Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/26/2012 09:00 PM, Anthony Liguori wrote: >>> Yes, that's one reason. But maybe a user wants to have a whole >>> different set of machine types and doesn't care to have the ones we >>> provide. Why prevent a user from doing this? >> >> How are we preventing a user from doing it? In what way is -nodefconfig >> helping it? > > > Let me explain it in a different way, perhaps. > > We launch smbd in QEMU in order to do file sharing over slirp. One of > the historic problems we've had is that we don't assume root > privileges, yet want to be able to run smbd without using any of the > system configuration files. > > You can do this by specify -s with the config file, and then in the > config file you can overload the various default paths (like private > dir, lock dir, etc.). In some cases, earlier versions of smbd didn't > allow you to change private dir. > > You should be able to tell a well behaved tool not to read any > configuration/data files and explicitly tell it where/how to read > them. We cannot exhaustively anticipate every future use case of QEMU. 100% agree. But that says nothing about a text file that defines "westmere" as a set of cpu flags, as long as we allow the user to define "mywestmere" as a different set. That is because target-x86_64.cfg does not configure anything, it just defines a macro, which qemu doesn't force you to use. > > But beyond the justification for -nodefconfig, the fact is that it > exists today, and has a specific semantic. If we want to have a > different semantic, we should introduce a new option (-no-user-config). Sure. -- error compiling committee.c: too many arguments to function -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/26/2012 09:03 PM, Anthony Liguori wrote: > > I think what we want to move toward is a -no-machine option which > allows a user to explicitly build a machine from scratch. That is: > > qemu -no-machine -device i440fx,id=host -device isa-serial,chr=chr0 ... > I'd call it -M bare-1.1, so that it can be used to override driver properties in 1.2+. So we'd have # default machine for this version qemu / qemu -M pc # an older version's pc qemu -M pc-1.1 # just a chassis, bring your own screwdriver qemu -M bare # previous generation chassis, beige qemu -M bare-1.1 That is because -M not only specifies the components that go into the machine, it also alters other devices you add to it. This also helps preserve the planet's dwindling supply of command line options. -- error compiling committee.c: too many arguments to function -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/26/2012 11:14 AM, Eduardo Habkost wrote: On Mon, Mar 26, 2012 at 02:03:21PM +0200, Gleb Natapov wrote: On Mon, Mar 26, 2012 at 01:59:05PM +0200, Avi Kivity wrote: On 03/26/2012 01:24 PM, Jiri Denemark wrote: ... The command line becomes unstable if you use -nodefconfig. -no-user-config solves this but I fully expect libvirt would continue to use -nodefconfig. Libvirt uses -nodefaults -nodefconfig because it wants to fully control how the virtual machine will look like (mainly in terms of devices). In other words, we don't want any devices to just magically appear without libvirt knowing about them. -nodefaults gets rid of default devices that are built directly in qemu. Since users can set any devices or command line options (such as enable-kvm) into qemu configuration files in @SYSCONFDIR@, we need to avoid reading those files as well. Hence we use -nodefconfig. However, we would still like qemu to read CPU definitions, machine types, etc. once they become externally loaded configuration (or however we decide to call it). That said, when CPU definitions are moved into @DATADIR@, and -no-user-config is introduced, I don't see any reason for libvirt to keep using -nodefconfig. ACK. I actually like -no-user-config more than -nodefconfig -readconfig @DATADIR@/... since it would avoid additional magic to detect what files libvirt should explicitly pass to -readconfig but basically any approach that would allow us to do read files only from @DATADIR@ is much better than what we have with -nodefconfig now. That's how I see it as well. +1 except that instead of -no-user-config we can do what most other programs do. If config file is specified during invocation default one is not used. After implementing -no-user-config (or similar) we can drop -nodefconfig entirely since its only user will be gone it its semantics is not clear. Awesome. It looks like we have a solution now? Anthony, do you agree with that? Daniel, it looks good for you? We cannot and should not drop -nodefconfig. But yes, I agree that we should introduce -no-user-config and use the semantics I specified earlier in the thread. Regards, Anthony Liguori -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/26/2012 04:08 AM, Avi Kivity wrote: If I see something like -nodefconfig, I assume it will create a bare bones guest that will not depend on any qemu defaults and will be stable across releases. That's not even close to what -nodefconfig is. That's pretty much what -nodefaults is but -nodefaults has also had a fluid definition historically. Okay. Let's just make sure to document -nodefconfig as version specific and -nodefaults as the stable way to create a bare bones guest (and define exactly what that means). Agreed. But I do want to point out, that -nodefaults has not been stable and since it doesn't universally create a bare bones guest, it's not clear that it will be. I think what we want to move toward is a -no-machine option which allows a user to explicitly build a machine from scratch. That is: qemu -no-machine -device i440fx,id=host -device isa-serial,chr=chr0 ... Regards, Anthony Liguori -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/25/2012 01:09 PM, Avi Kivity wrote: Suppose we define the southbridge via a configuration file. Does that mean we don't load it any more? Yes. If I want the leanest and meanest version of QEMU that will start in the smallest number of milliseconds, then being able to tell QEMU not to load configuration files and create a very specific machine is a Good Thing. Why exclude users from being able to do this? So is this the point? Reducing startup time? Yes, that's one reason. But maybe a user wants to have a whole different set of machine types and doesn't care to have the ones we provide. Why prevent a user from doing this? How are we preventing a user from doing it? In what way is -nodefconfig helping it? Let me explain it in a different way, perhaps. We launch smbd in QEMU in order to do file sharing over slirp. One of the historic problems we've had is that we don't assume root privileges, yet want to be able to run smbd without using any of the system configuration files. You can do this by specify -s with the config file, and then in the config file you can overload the various default paths (like private dir, lock dir, etc.). In some cases, earlier versions of smbd didn't allow you to change private dir. You should be able to tell a well behaved tool not to read any configuration/data files and explicitly tell it where/how to read them. We cannot exhaustively anticipate every future use case of QEMU. But beyond the justification for -nodefconfig, the fact is that it exists today, and has a specific semantic. If we want to have a different semantic, we should introduce a new option (-no-user-config). Regards, Anthony Liguori Maybe they have a management tool that attempts to totally hide QEMU from the end user and exposes a different set of machine types. It's certainly more convenient for something like the Android emulator to only have to deal with QEMU knowing about the 4 types of machines that it specifically supports. If it supports four types, it should always pass one of them to qemu. The only thing -nodefconfig adds is breakage when qemu moves something that one of those four machines relies on to a config file. -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Sun, Mar 25, 2012 at 01:11:04PM -0500, Anthony Liguori wrote: > On 03/25/2012 10:40 AM, Avi Kivity wrote: > >On 03/25/2012 05:26 PM, Anthony Liguori wrote: > >>>Put the emphasis around *configuration*. > >> > >> > >>So how about: > >> > >>1) Load ['@SYSCONFDIR@/qemu/qemu.cfg', > >>'@SYSCONFDIR@/qemu/target-@ARCH@.cfg', > >> '@DATADIR@/system.cfg', '@DATADIR@/system-@ARCH@.cfg'] > >> > >>2) system-@ARCH@.cfg will contain: > >> > >>[system] > >>readconfig=@DATADIR@/target-@a...@-cpus.cfg > >>readconfig=@DATADIR@/target-@a...@-machine.cfg > >> > >>3) -nodefconfig will not load any configuration files from DATADIR or > >>SYSCONFDIR. -no-user-config will not load any configuration files > >>from SYSCONFDIR. > > > >What, more options? > > Okay, we can just drop -no-user-config and then if a management tool > wants to do the equivalent, they can do -nodefconfig + '-readconfig > @DATADIR@/system-@ARCH@.cfg'. I'm equally happy with that :-) I actually prefer -no-user-config, because it gives Qemu freedom to add more stuff to the outside if needed, but without requiring more -readconfig options (or -read-something-else options, if we create them) to be added in the future. For example, if one day we move machine-types to external files, libvirt wouldn't have to be changed to add Yet Another -readconfig argument to make the machine-types available for use. If Qemu moves some device implementation to external modules, they won't suddenly go away for users of -no-user-config. The list of possible changes that would break compatibility for -nodefconfig users but no -no-user-config users is large. [...] > >I don't think -nodefconfig (as defined) is usable, since there is no way > >for the user to tell what it means short of reading those files. > > *if the user doesn't know specifics about this QEMU version. > > You make the assumption that all users are going to throw arbitrary > options at arbitrary QEMU versions. That's certainly an important > use-case but it's not the only one. Well, you make the assumption that somebody will every want to use -nodefconfig the way you want to define it. I don't think nobody will ever use it if we defined it that way, but that's OK with me. I will simply ignore the existence of -nodefconfig from now on. :-) [...] > >>>"#define westmere blah" is not configuration, otherwise the meaning of > >>>configuration will drift over time. > >>> > >>>-cpu blah is, of course. > >> > >>It's the same mechanism, but the above would create two classes of > >>default configuration files and then it becomes a question of how > >>they're used. > > > >Confused. > > We don't have a formal concept of -read-definition-config and > -read-configuration-config > > There's no easy or obvious way to create such a concept either nor do > I think the distinction is meaningful to users. The distinction _is_ meaningful to libvirt, that's what started this thread. [...] > >The file defines westmere as an alias for a grab bag of options. > >Whether it's loaded or not is immaterial, unless someone uses one > >of the > >names within. > > But you would agree, a management tool should be able to control > whether class factories get loaded, right? > >>> > >>>No, why? But perhaps I don't entirely get what you mean by "class > >>>factories". > >>> > >>>Aren't they just implementations of > >>> > >>> virtual Device *new_instance(...) = 0? > >>> > >>>if so, why not load them? > >> > >>No, a class factory creates a new type of class. -cpudef will > >>ultimately call type_register() to create a new QOM visible type. > >> From a management tools perspective, the type is no different than a > >>built-in type. > > > >Exactly. The types are no different, so there's no reason to > >discriminate against types that happen to live in qemu-provided data > >files vs. qemu code. They aren't instantiated, so we lose nothing by > >creating the factories (just so long as the factories aren't > >mass-producing objects). > > At some point, I'd like to have type modules that are shared objects. > I'd like QEMU to start with almost no builtin types and allow the > user to configure which modules get loaded. > > In the long term, I'd like QEMU to be a small, robust core with the > vast majority of code relegated to modules with the user ultimately > in control of module loading. > > Yes, I'd want some module autoloading system but there should always > be a way to launch QEMU without loading any modules and then load a > very specific set of modules (as defined by the user). And libvirt needs a way to keep module autoloading enabled while disabling the loading of files from /etc. > > You can imagine this being useful for something like Common Criteria > certifications. No problem, except that this is not the use-case libvirt has. If you want -nodefconfig to mean that, that's OK. But we need an option to just disable the loading of files from /etc, but keeping loading the "de
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Mon, Mar 26, 2012 at 02:03:21PM +0200, Gleb Natapov wrote: > On Mon, Mar 26, 2012 at 01:59:05PM +0200, Avi Kivity wrote: > > On 03/26/2012 01:24 PM, Jiri Denemark wrote: > > > ... > > > > > The command line becomes unstable if you use -nodefconfig. > > > > > > > > -no-user-config solves this but I fully expect libvirt would continue > > > > to use > > > > -nodefconfig. > > > > > > Libvirt uses -nodefaults -nodefconfig because it wants to fully control > > > how > > > the virtual machine will look like (mainly in terms of devices). In other > > > words, we don't want any devices to just magically appear without libvirt > > > knowing about them. -nodefaults gets rid of default devices that are built > > > directly in qemu. Since users can set any devices or command line options > > > (such as enable-kvm) into qemu configuration files in @SYSCONFDIR@, we > > > need to > > > avoid reading those files as well. Hence we use -nodefconfig. However, we > > > would still like qemu to read CPU definitions, machine types, etc. once > > > they > > > become externally loaded configuration (or however we decide to call it). > > > That > > > said, when CPU definitions are moved into @DATADIR@, and -no-user-config > > > is > > > introduced, I don't see any reason for libvirt to keep using -nodefconfig. ACK. > > > > > > I actually like > > > -no-user-config > > > more than > > > -nodefconfig -readconfig @DATADIR@/... > > > since it would avoid additional magic to detect what files libvirt should > > > explicitly pass to -readconfig but basically any approach that would > > > allow us > > > to do read files only from @DATADIR@ is much better than what we have with > > > -nodefconfig now. > > > > That's how I see it as well. > > > +1 > > except that instead of -no-user-config we can do what most other > programs do. If config file is specified during invocation default one > is not used. After implementing -no-user-config (or similar) we can drop > -nodefconfig entirely since its only user will be gone it its semantics > is not clear. Awesome. It looks like we have a solution now? Anthony, do you agree with that? Daniel, it looks good for you? It looks like in the end, no one will ever use -nodefconfig because it's optimizing for a use-case that nobody cares about. Maybe I'm wrong and somebody somewhere will use -nodefconfig, maybe Anthony has a specific use-case or specific tools in mind, I don't know. But personally I will probably simply ignore the existence of -nodefconfig because it is absolutely useless for me and for libvirt. -- Eduardo -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Sun, Mar 25, 2012 at 12:19:13PM +0200, Gleb Natapov wrote: > > (That's why I said that perhaps keymaps could become configuration > > someday. Because maybe they can be converted to a key=value model > > relatively easily) > > > Such whole sale approach is harmful since it starts to affect design > decisions. So now if it seams logical to move something outside the code > one can decide against it just because it will become "configuration" > due to that design. This is one point I agree completely with. There's no reason to couple the decision to "move something to an external file" with making changes to the Qemu external interfaces. We should be able to gradually move things to be "data" without breaking the expectations of libvirt at the same time. We must be able to make a gradual design change, where we first move data to an external file without making that change visible to the outside, then slowly try to make it part of the user-visible configuration (that means making externally visible interface changes, something that has to be made much more carefully than just moving "internal data" around). Anthony seems to be simply rejecting the possibility of doing this gradual change[1]. [1] I still need to read this whole thread, so sorry if I am wrong. -- Eduardo -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Mon, Mar 26, 2012 at 01:59:05PM +0200, Avi Kivity wrote: > On 03/26/2012 01:24 PM, Jiri Denemark wrote: > > ... > > > > The command line becomes unstable if you use -nodefconfig. > > > > > > -no-user-config solves this but I fully expect libvirt would continue to > > > use > > > -nodefconfig. > > > > Libvirt uses -nodefaults -nodefconfig because it wants to fully control how > > the virtual machine will look like (mainly in terms of devices). In other > > words, we don't want any devices to just magically appear without libvirt > > knowing about them. -nodefaults gets rid of default devices that are built > > directly in qemu. Since users can set any devices or command line options > > (such as enable-kvm) into qemu configuration files in @SYSCONFDIR@, we need > > to > > avoid reading those files as well. Hence we use -nodefconfig. However, we > > would still like qemu to read CPU definitions, machine types, etc. once they > > become externally loaded configuration (or however we decide to call it). > > That > > said, when CPU definitions are moved into @DATADIR@, and -no-user-config is > > introduced, I don't see any reason for libvirt to keep using -nodefconfig. > > > > I actually like > > -no-user-config > > more than > > -nodefconfig -readconfig @DATADIR@/... > > since it would avoid additional magic to detect what files libvirt should > > explicitly pass to -readconfig but basically any approach that would allow > > us > > to do read files only from @DATADIR@ is much better than what we have with > > -nodefconfig now. > > That's how I see it as well. > +1 except that instead of -no-user-config we can do what most other programs do. If config file is specified during invocation default one is not used. After implementing -no-user-config (or similar) we can drop -nodefconfig entirely since its only user will be gone it its semantics is not clear. -- Gleb. -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/26/2012 01:24 PM, Jiri Denemark wrote: > ... > > > The command line becomes unstable if you use -nodefconfig. > > > > -no-user-config solves this but I fully expect libvirt would continue to > > use > > -nodefconfig. > > Libvirt uses -nodefaults -nodefconfig because it wants to fully control how > the virtual machine will look like (mainly in terms of devices). In other > words, we don't want any devices to just magically appear without libvirt > knowing about them. -nodefaults gets rid of default devices that are built > directly in qemu. Since users can set any devices or command line options > (such as enable-kvm) into qemu configuration files in @SYSCONFDIR@, we need to > avoid reading those files as well. Hence we use -nodefconfig. However, we > would still like qemu to read CPU definitions, machine types, etc. once they > become externally loaded configuration (or however we decide to call it). That > said, when CPU definitions are moved into @DATADIR@, and -no-user-config is > introduced, I don't see any reason for libvirt to keep using -nodefconfig. > > I actually like > -no-user-config > more than > -nodefconfig -readconfig @DATADIR@/... > since it would avoid additional magic to detect what files libvirt should > explicitly pass to -readconfig but basically any approach that would allow us > to do read files only from @DATADIR@ is much better than what we have with > -nodefconfig now. That's how I see it as well. -- error compiling committee.c: too many arguments to function -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Sun, Mar 25, 2012 at 10:26:57 -0500, Anthony Liguori wrote: > On 03/25/2012 10:16 AM, Avi Kivity wrote: > > On 03/25/2012 04:59 PM, Anthony Liguori wrote: > So how about: > > 1) Load ['@SYSCONFDIR@/qemu/qemu.cfg', '@SYSCONFDIR@/qemu/target-@ARCH@.cfg', > '@DATADIR@/system.cfg', '@DATADIR@/system-@ARCH@.cfg'] > > 2) system-@ARCH@.cfg will contain: > > [system] > readconfig=@DATADIR@/target-@a...@-cpus.cfg > readconfig=@DATADIR@/target-@a...@-machine.cfg > > 3) -nodefconfig will not load any configuration files from DATADIR or > SYSCONFDIR. -no-user-config will not load any configuration files from > SYSCONFDIR. > ... > > The command line becomes unstable if you use -nodefconfig. > > -no-user-config solves this but I fully expect libvirt would continue to use > -nodefconfig. Libvirt uses -nodefaults -nodefconfig because it wants to fully control how the virtual machine will look like (mainly in terms of devices). In other words, we don't want any devices to just magically appear without libvirt knowing about them. -nodefaults gets rid of default devices that are built directly in qemu. Since users can set any devices or command line options (such as enable-kvm) into qemu configuration files in @SYSCONFDIR@, we need to avoid reading those files as well. Hence we use -nodefconfig. However, we would still like qemu to read CPU definitions, machine types, etc. once they become externally loaded configuration (or however we decide to call it). That said, when CPU definitions are moved into @DATADIR@, and -no-user-config is introduced, I don't see any reason for libvirt to keep using -nodefconfig. I actually like -no-user-config more than -nodefconfig -readconfig @DATADIR@/... since it would avoid additional magic to detect what files libvirt should explicitly pass to -readconfig but basically any approach that would allow us to do read files only from @DATADIR@ is much better than what we have with -nodefconfig now. Jirka -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Mon, Mar 26, 2012 at 11:08:16AM +0200, Avi Kivity wrote: > >> Exactly. The types are no different, so there's no reason to > >> discriminate against types that happen to live in qemu-provided data > >> files vs. qemu code. They aren't instantiated, so we lose nothing by > >> creating the factories (just so long as the factories aren't > >> mass-producing objects). > > > > > > At some point, I'd like to have type modules that are shared objects. > > I'd like QEMU to start with almost no builtin types and allow the user > > to configure which modules get loaded. > > > > In the long term, I'd like QEMU to be a small, robust core with the > > vast majority of code relegated to modules with the user ultimately in > > control of module loading. > > > > Yes, I'd want some module autoloading system but there should always > > be a way to launch QEMU without loading any modules and then load a > > very specific set of modules (as defined by the user). > > > > You can imagine this being useful for something like Common Criteria > > certifications. > > Okay. > Modularised minimal QEMU may be a good thing, but how -nodefconfig helps here? Won't you have the same effect if QEMU will load modules on demand, only when they are actually needed (regardless of -nodefconfig). i.e virtio-blk is loaded only if there is -device virtio-blk somewhere in configuration. > > It's obviously defined for a given release, just not defined long term. > > > >> If I see something like -nodefconfig, I assume it will create a bare > >> bones guest that will not depend on any qemu defaults and will be stable > >> across releases. > > > > That's not even close to what -nodefconfig is. That's pretty much > > what -nodefaults is but -nodefaults has also had a fluid definition > > historically. > > Okay. Let's just make sure to document -nodefconfig as version specific > and -nodefaults as the stable way to create a bare bones guest (and > define exactly what that means). > What is the reason libvirt uses -nodefconfig instead of -nodefaults now? What the former does for them that the later doesn't? -- Gleb. -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/25/2012 08:11 PM, Anthony Liguori wrote: > >> I don't think -nodefconfig (as defined) is usable, since there is no way >> for the user to tell what it means short of reading those files. > > *if the user doesn't know specifics about this QEMU version. > > You make the assumption that all users are going to throw arbitrary > options at arbitrary QEMU versions. That's certainly an important > use-case but it's not the only one. If a Fedora user is using qemu, then their qemu version will change every six months. Their options are to update their scripts/management tool in step, or not have their management tool use -nodefconfig. The same holds for anyone using qemu from upstream, since that's approximately the qemu release cycle. > >> -no-user-config is usable, I think it needs also to mean that qemu >> without -M/-cpu/-m options will error out? > > You're confusing -nodefaults (or something stronger than -nodefaults) > with -no-user-config. > Right. > Yes, the distinctions are confusing. It's not all fixable tomorrow. > If we take my config refactoring series, we can get 90% of the way > there soon but Paolo has a more thorough refactoring.. > "#define westmere blah" is not configuration, otherwise the meaning of configuration will drift over time. -cpu blah is, of course. >>> >>> It's the same mechanism, but the above would create two classes of >>> default configuration files and then it becomes a question of how >>> they're used. >> >> Confused. > > We don't have a formal concept of -read-definition-config and > -read-configuration-config > > There's no easy or obvious way to create such a concept either nor do > I think the distinction is meaningful to users. Definition files should be invisible to users. They're part of the implementation. If we have a file that says pc-1.1 = piix + cirrus + memory(128) + ... then it's nobody's business if it's in a text file or a .c file. Of course it's nice to allow users to load their own definition files, but that's strictly a convenience. >> Exactly. The types are no different, so there's no reason to >> discriminate against types that happen to live in qemu-provided data >> files vs. qemu code. They aren't instantiated, so we lose nothing by >> creating the factories (just so long as the factories aren't >> mass-producing objects). > > > At some point, I'd like to have type modules that are shared objects. > I'd like QEMU to start with almost no builtin types and allow the user > to configure which modules get loaded. > > In the long term, I'd like QEMU to be a small, robust core with the > vast majority of code relegated to modules with the user ultimately in > control of module loading. > > Yes, I'd want some module autoloading system but there should always > be a way to launch QEMU without loading any modules and then load a > very specific set of modules (as defined by the user). > > You can imagine this being useful for something like Common Criteria > certifications. Okay. > It's obviously defined for a given release, just not defined long term. > >> If I see something like -nodefconfig, I assume it will create a bare >> bones guest that will not depend on any qemu defaults and will be stable >> across releases. > > That's not even close to what -nodefconfig is. That's pretty much > what -nodefaults is but -nodefaults has also had a fluid definition > historically. Okay. Let's just make sure to document -nodefconfig as version specific and -nodefaults as the stable way to create a bare bones guest (and define exactly what that means). -- error compiling committee.c: too many arguments to function -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/25/2012 08:01 PM, Anthony Liguori wrote: >> I don't think this came out of happiness, but despair. Seriously, >> keeping compatibility is one of the things we work hardest to achieve, >> and we can't manage it for our command line? > > > I hate to burst your bubble, but we struggle and rarely maintain the > level of compatibility you're seeking to have. > > I agree with you that we need to do a better job maintaining > compatibility which is why I'm trying to clearly separate the things > that we will never break from the things that will change over time. > > -nodefconfig is a moving target. If you want stability, don't use > it. If you just want to prevent the user's /etc/qemu stuff from being > loaded, use -no-user-config. Fine, but let's clearly document it as such. Note just saying it doesn't load any configuration files isn't sufficient. We have to say that it kills Westmere and some of its friends, but preserves others like qemu64. Otherwise it's impossible to use it except by trial and error. > >>> >>> I'm not saying that backwards compat isn't important--it is. But >>> there are users who are happy to live on the bleeding edge. >> >> That's fine, but I don't see how -nodefconfig helps them. All it does >> is take away the building blocks (definitions) that they can use when >> setting up their configuration. > > Yes, this is a feature. I don't see how, but okay. > Suppose we define the southbridge via a configuration file. Does that mean we don't load it any more? >>> >>> Yes. If I want the leanest and meanest version of QEMU that will >>> start in the smallest number of milliseconds, then being able to tell >>> QEMU not to load configuration files and create a very specific >>> machine is a Good Thing. Why exclude users from being able to do this? >> >> So is this the point? Reducing startup time? > > Yes, that's one reason. But maybe a user wants to have a whole > different set of machine types and doesn't care to have the ones we > provide. Why prevent a user from doing this? How are we preventing a user from doing it? In what way is -nodefconfig helping it? > Maybe they have a management tool that attempts to totally hide QEMU > from the end user and exposes a different set of machine types. It's > certainly more convenient for something like the Android emulator to > only have to deal with QEMU knowing about the 4 types of machines that > it specifically supports. If it supports four types, it should always pass one of them to qemu. The only thing -nodefconfig adds is breakage when qemu moves something that one of those four machines relies on to a config file. -- error compiling committee.c: too many arguments to function -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/25/2012 10:40 AM, Avi Kivity wrote: On 03/25/2012 05:26 PM, Anthony Liguori wrote: Put the emphasis around *configuration*. So how about: 1) Load ['@SYSCONFDIR@/qemu/qemu.cfg', '@SYSCONFDIR@/qemu/target-@ARCH@.cfg', '@DATADIR@/system.cfg', '@DATADIR@/system-@ARCH@.cfg'] 2) system-@ARCH@.cfg will contain: [system] readconfig=@DATADIR@/target-@a...@-cpus.cfg readconfig=@DATADIR@/target-@a...@-machine.cfg 3) -nodefconfig will not load any configuration files from DATADIR or SYSCONFDIR. -no-user-config will not load any configuration files from SYSCONFDIR. What, more options? Okay, we can just drop -no-user-config and then if a management tool wants to do the equivalent, they can do -nodefconfig + '-readconfig @DATADIR@/system-@ARCH@.cfg'. I'm equally happy with that :-) I don't think -nodefconfig (as defined) is usable, since there is no way for the user to tell what it means short of reading those files. *if the user doesn't know specifics about this QEMU version. You make the assumption that all users are going to throw arbitrary options at arbitrary QEMU versions. That's certainly an important use-case but it's not the only one. -no-user-config is usable, I think it needs also to mean that qemu without -M/-cpu/-m options will error out? You're confusing -nodefaults (or something stronger than -nodefaults) with -no-user-config. Yes, the distinctions are confusing. It's not all fixable tomorrow. If we take my config refactoring series, we can get 90% of the way there soon but Paolo has a more thorough refactoring.. "#define westmere blah" is not configuration, otherwise the meaning of configuration will drift over time. -cpu blah is, of course. It's the same mechanism, but the above would create two classes of default configuration files and then it becomes a question of how they're used. Confused. We don't have a formal concept of -read-definition-config and -read-configuration-config There's no easy or obvious way to create such a concept either nor do I think the distinction is meaningful to users. The file defines westmere as an alias for a grab bag of options. Whether it's loaded or not is immaterial, unless someone uses one of the names within. But you would agree, a management tool should be able to control whether class factories get loaded, right? No, why? But perhaps I don't entirely get what you mean by "class factories". Aren't they just implementations of virtual Device *new_instance(...) = 0? if so, why not load them? No, a class factory creates a new type of class. -cpudef will ultimately call type_register() to create a new QOM visible type. From a management tools perspective, the type is no different than a built-in type. Exactly. The types are no different, so there's no reason to discriminate against types that happen to live in qemu-provided data files vs. qemu code. They aren't instantiated, so we lose nothing by creating the factories (just so long as the factories aren't mass-producing objects). At some point, I'd like to have type modules that are shared objects. I'd like QEMU to start with almost no builtin types and allow the user to configure which modules get loaded. In the long term, I'd like QEMU to be a small, robust core with the vast majority of code relegated to modules with the user ultimately in control of module loading. Yes, I'd want some module autoloading system but there should always be a way to launch QEMU without loading any modules and then load a very specific set of modules (as defined by the user). You can imagine this being useful for something like Common Criteria certifications. Otherwise, the meaning of -nodefconfig changes as more stuff is moved out of .c and into .cfg. What's the problem with this? The command line becomes unstable if you use -nodefconfig. -no-user-config solves this but I fully expect libvirt would continue to use -nodefconfig. I don't see how libvirt can use -nodefconfig with the fluid meaning you attach to it, or what it gains from it. -nodefconfig = create an empty machine, don't assume anything (=don't read qemu.cfg) let me build it out of all those lego bricks. Those can be defined in code or in definition files in /usr/share, I don't care. Maybe that's -nodevices -vga none. But in this case I don't see the point in -nodefconfig. Not loading target_x86-64.cfg doesn't buy the user anything, since it wouldn't affect the guest in any way. -nodefconfig doesn't mean what you think it means. -nodefconfig doesn't say anything about the user visible machine. -nodefconfig tells QEMU not to read any configuration files at start up. This has an undefined affect on the user visible machine that depends on the specific version of QEMU. Then it's broken. How can anyone use something that has an undefined effect? It's obviously defined for a given release, just not defined long term. If I see something like -
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/25/2012 10:45 AM, Avi Kivity wrote: On 03/25/2012 05:30 PM, Anthony Liguori wrote: On 03/25/2012 10:18 AM, Avi Kivity wrote: On 03/25/2012 05:07 PM, Anthony Liguori wrote: As log as qemu -nodefconfig -cpu westmere -M pc1.1 -nodefconfig is going to eventually mean that -cpu westmere and -M pc-1.1 will not work. This is where QEMU is going. There is no reason that a normal user should ever use -nodefconfig. I don't think anyone or anything can use it, since it's meaning is not well defined. "not read any configuration files" where parts of qemu are continually moved out to configuration files means its a moving target. I think you assume that all QEMU users care about forward and backwards compatibility on the command line about all else. That's really not true. The libvirt folks have stated repeatedly that command line backwards compatibility is not critical to them. They are happy to require that a new version of QEMU requires a new version of libvirt. I don't think this came out of happiness, but despair. Seriously, keeping compatibility is one of the things we work hardest to achieve, and we can't manage it for our command line? I hate to burst your bubble, but we struggle and rarely maintain the level of compatibility you're seeking to have. I agree with you that we need to do a better job maintaining compatibility which is why I'm trying to clearly separate the things that we will never break from the things that will change over time. -nodefconfig is a moving target. If you want stability, don't use it. If you just want to prevent the user's /etc/qemu stuff from being loaded, use -no-user-config. I'm not saying that backwards compat isn't important--it is. But there are users who are happy to live on the bleeding edge. That's fine, but I don't see how -nodefconfig helps them. All it does is take away the building blocks (definitions) that they can use when setting up their configuration. Yes, this is a feature. Suppose we define the southbridge via a configuration file. Does that mean we don't load it any more? Yes. If I want the leanest and meanest version of QEMU that will start in the smallest number of milliseconds, then being able to tell QEMU not to load configuration files and create a very specific machine is a Good Thing. Why exclude users from being able to do this? So is this the point? Reducing startup time? Yes, that's one reason. But maybe a user wants to have a whole different set of machine types and doesn't care to have the ones we provide. Why prevent a user from doing this? Maybe they have a management tool that attempts to totally hide QEMU from the end user and exposes a different set of machine types. It's certainly more convenient for something like the Android emulator to only have to deal with QEMU knowing about the 4 types of machines that it specifically supports. Regards, Anthony Liguori -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/25/2012 03:26 PM, Anthony Liguori wrote: >>> We would continue to have Westmere/etc in QEMU exposed as part of the >>> user configuration. But I don't think it makes a lot of sense to have >>> to modify QEMU any time a new CPU comes out. >> >> We have to. New features often come with new MSRs which need to be live >> migrated, and of course the cpu flags as well. We may push all these to >> qemu data files, but this is still qemu. We can't let a management tool >> decide that cpu feature X is safe to use on qemu version Y. > > > I think QEMU should own CPU definitions. Agree. > I think a management tool should have the choice of whether they are > used though because they are a policy IMHO. > > It's okay for QEMU to implement some degree of policy as long as a > management tool can override it with a different policy. Sure. We can have something like # default machine's westmere qemu -cpu westmere # pc-1.0's westmere qemu -M pc-1.0 -cpu westmere # pc-1.0's westmere, without nx-less qemu -M pc-1.0 -cpu westmere,-nx # specify everything in painful detail qemu -cpu vendor=Foo,family=17,model=19,stepping=3,maxleaf=12,+fpu,+vme,leaf10eax=0x1234567,+etc -- error compiling committee.c: too many arguments to function -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/25/2012 05:30 PM, Anthony Liguori wrote: > On 03/25/2012 10:18 AM, Avi Kivity wrote: >> On 03/25/2012 05:07 PM, Anthony Liguori wrote: As log as qemu -nodefconfig -cpu westmere -M pc1.1 >>> >>> >>> -nodefconfig is going to eventually mean that -cpu westmere and -M >>> pc-1.1 will not work. >>> >>> This is where QEMU is going. There is no reason that a normal user >>> should ever use -nodefconfig. >> >> I don't think anyone or anything can use it, since it's meaning is not >> well defined. "not read any configuration files" where parts of qemu >> are continually moved out to configuration files means its a moving >> target. > > I think you assume that all QEMU users care about forward and > backwards compatibility on the command line about all else. > > That's really not true. The libvirt folks have stated repeatedly that > command line backwards compatibility is not critical to them. They > are happy to require that a new version of QEMU requires a new version > of libvirt. I don't think this came out of happiness, but despair. Seriously, keeping compatibility is one of the things we work hardest to achieve, and we can't manage it for our command line? > > I'm not saying that backwards compat isn't important--it is. But > there are users who are happy to live on the bleeding edge. That's fine, but I don't see how -nodefconfig helps them. All it does is take away the building blocks (definitions) that they can use when setting up their configuration. > >> Suppose we define the southbridge via a configuration file. Does that >> mean we don't load it any more? > > Yes. If I want the leanest and meanest version of QEMU that will > start in the smallest number of milliseconds, then being able to tell > QEMU not to load configuration files and create a very specific > machine is a Good Thing. Why exclude users from being able to do this? So is this the point? Reducing startup time? I can't say I see the reason to invest so much effort in shaving a millisecond or less from this, but if we did want to, the way would be lazy loading of the configuration where items are parsed as they are referenced. -- error compiling committee.c: too many arguments to function -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/25/2012 05:26 PM, Anthony Liguori wrote: >> Put the emphasis around *configuration*. > > > So how about: > > 1) Load ['@SYSCONFDIR@/qemu/qemu.cfg', > '@SYSCONFDIR@/qemu/target-@ARCH@.cfg', > '@DATADIR@/system.cfg', '@DATADIR@/system-@ARCH@.cfg'] > > 2) system-@ARCH@.cfg will contain: > > [system] > readconfig=@DATADIR@/target-@a...@-cpus.cfg > readconfig=@DATADIR@/target-@a...@-machine.cfg > > 3) -nodefconfig will not load any configuration files from DATADIR or > SYSCONFDIR. -no-user-config will not load any configuration files > from SYSCONFDIR. What, more options? I don't think -nodefconfig (as defined) is usable, since there is no way for the user to tell what it means short of reading those files. -no-user-config is usable, I think it needs also to mean that qemu without -M/-cpu/-m options will error out? since the default machine/cpu types are default configuration. > >> "#define westmere blah" is not configuration, otherwise the meaning of >> configuration will drift over time. >> >> -cpu blah is, of course. > > It's the same mechanism, but the above would create two classes of > default configuration files and then it becomes a question of how > they're used. Confused. > The file defines westmere as an alias for a grab bag of options. Whether it's loaded or not is immaterial, unless someone uses one of the names within. >>> >>> But you would agree, a management tool should be able to control >>> whether class factories get loaded, right? >> >> No, why? But perhaps I don't entirely get what you mean by "class >> factories". >> >> Aren't they just implementations of >> >> virtual Device *new_instance(...) = 0? >> >> if so, why not load them? > > No, a class factory creates a new type of class. -cpudef will > ultimately call type_register() to create a new QOM visible type. > From a management tools perspective, the type is no different than a > built-in type. Exactly. The types are no different, so there's no reason to discriminate against types that happen to live in qemu-provided data files vs. qemu code. They aren't instantiated, so we lose nothing by creating the factories (just so long as the factories aren't mass-producing objects). > Otherwise, the meaning of -nodefconfig changes as more stuff is moved out of .c and into .cfg. >>> >>> What's the problem with this? >> >> The command line becomes unstable if you use -nodefconfig. > > -no-user-config solves this but I fully expect libvirt would continue > to use -nodefconfig. I don't see how libvirt can use -nodefconfig with the fluid meaning you attach to it, or what it gains from it. >> >> -nodefconfig = create an empty machine, don't assume anything (=don't >> read qemu.cfg) let me build it out of all those lego bricks. Those can >> be defined in code or in definition files in /usr/share, I don't care. >> >> Maybe that's -nodevices -vga none. But in this case I don't see the >> point in -nodefconfig. Not loading target_x86-64.cfg doesn't buy the >> user anything, since it wouldn't affect the guest in any way. > > > -nodefconfig doesn't mean what you think it means. -nodefconfig > doesn't say anything about the user visible machine. > > -nodefconfig tells QEMU not to read any configuration files at start > up. This has an undefined affect on the user visible machine that > depends on the specific version of QEMU. Then it's broken. How can anyone use something that has an undefined effect? If I see something like -nodefconfig, I assume it will create a bare bones guest that will not depend on any qemu defaults and will be stable across releases. I don't think anyone will understand -nodefconfig to be something version dependent without reading the qemu management tool author's guide. -- error compiling committee.c: too many arguments to function -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/25/2012 10:18 AM, Avi Kivity wrote: On 03/25/2012 05:07 PM, Anthony Liguori wrote: As log as qemu -nodefconfig -cpu westmere -M pc1.1 -nodefconfig is going to eventually mean that -cpu westmere and -M pc-1.1 will not work. This is where QEMU is going. There is no reason that a normal user should ever use -nodefconfig. I don't think anyone or anything can use it, since it's meaning is not well defined. "not read any configuration files" where parts of qemu are continually moved out to configuration files means its a moving target. I think you assume that all QEMU users care about forward and backwards compatibility on the command line about all else. That's really not true. The libvirt folks have stated repeatedly that command line backwards compatibility is not critical to them. They are happy to require that a new version of QEMU requires a new version of libvirt. I'm not saying that backwards compat isn't important--it is. But there are users who are happy to live on the bleeding edge. Suppose we define the southbridge via a configuration file. Does that mean we don't load it any more? Yes. If I want the leanest and meanest version of QEMU that will start in the smallest number of milliseconds, then being able to tell QEMU not to load configuration files and create a very specific machine is a Good Thing. Why exclude users from being able to do this? Regards, Anthony Liguori -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/25/2012 10:16 AM, Avi Kivity wrote: On 03/25/2012 04:59 PM, Anthony Liguori wrote: On 03/25/2012 09:46 AM, Avi Kivity wrote: On 03/25/2012 04:36 PM, Anthony Liguori wrote: Apart from the command line length, it confuses configuration with definition. There is no distinction with what we have today. Our configuration file basically corresponds to command line options and as there is no distinction in command line options, there's no distinction in the configuration format. We don't have command line options for defining, only configuring. That's an oversight. There should be a -cpudef option. It's a QemuOptsList. Again, defining = #define I think -global fits your definition of #define... Yes (apart from the corner case of modifying a default-instantiated device). B) A management tool has complete control over cpu definitions without modifying the underlying filesystem. -nodefconfig will prevent it from loading and the management tool can explicitly load the QEMU definition (via -readconfig, potentially using a /dev/fd/N path) or it can define it's own cpu definitions. Why does -nodefconfig affect anything? Because -nodefconfig means "don't load *any* default configuration files". Put the emphasis around *configuration*. So how about: 1) Load ['@SYSCONFDIR@/qemu/qemu.cfg', '@SYSCONFDIR@/qemu/target-@ARCH@.cfg', '@DATADIR@/system.cfg', '@DATADIR@/system-@ARCH@.cfg'] 2) system-@ARCH@.cfg will contain: [system] readconfig=@DATADIR@/target-@a...@-cpus.cfg readconfig=@DATADIR@/target-@a...@-machine.cfg 3) -nodefconfig will not load any configuration files from DATADIR or SYSCONFDIR. -no-user-config will not load any configuration files from SYSCONFDIR. "#define westmere blah" is not configuration, otherwise the meaning of configuration will drift over time. -cpu blah is, of course. It's the same mechanism, but the above would create two classes of default configuration files and then it becomes a question of how they're used. The file defines westmere as an alias for a grab bag of options. Whether it's loaded or not is immaterial, unless someone uses one of the names within. But you would agree, a management tool should be able to control whether class factories get loaded, right? No, why? But perhaps I don't entirely get what you mean by "class factories". Aren't they just implementations of virtual Device *new_instance(...) = 0? if so, why not load them? No, a class factory creates a new type of class. -cpudef will ultimately call type_register() to create a new QOM visible type. From a management tools perspective, the type is no different than a built-in type. Otherwise, the meaning of -nodefconfig changes as more stuff is moved out of .c and into .cfg. What's the problem with this? The command line becomes unstable if you use -nodefconfig. -no-user-config solves this but I fully expect libvirt would continue to use -nodefconfig. In my target-$(ARCH).cfg, I have: [machine] enable-kvm = "on" Which means I don't have to use -enable-kvm anymore. But if you look at a tool like libguestfs, start up time is the most important thing so avoiding unnecessary I/O and processing is critical. So this is definitely configuration (applies to the current instance) as opposed to target-x86_64.cfg, which doesn't. I'm not sure which part you're responding to.. I was saying that target-x86_64.cfg appears to be definitions, not configuration, and was asking about qemu.cfg (which is configuration). As far as I can tell, the only difference is that -nodefconfig -cpu westmere will error out instead of working. But if you don't supply -cpu westmere, the configuration is identical. What configuration? Let me ask, what do you think the semantics of -nodefconfig should be? I'm not sure I understand what you're advocating for. -nodefconfig = create an empty machine, don't assume anything (=don't read qemu.cfg) let me build it out of all those lego bricks. Those can be defined in code or in definition files in /usr/share, I don't care. Maybe that's -nodevices -vga none. But in this case I don't see the point in -nodefconfig. Not loading target_x86-64.cfg doesn't buy the user anything, since it wouldn't affect the guest in any way. -nodefconfig doesn't mean what you think it means. -nodefconfig doesn't say anything about the user visible machine. -nodefconfig tells QEMU not to read any configuration files at start up. This has an undefined affect on the user visible machine that depends on the specific version of QEMU. Regards, Anthony Liguori -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/25/2012 05:07 PM, Anthony Liguori wrote: >> As log as qemu -nodefconfig -cpu westmere -M pc1.1 > > > -nodefconfig is going to eventually mean that -cpu westmere and -M > pc-1.1 will not work. > > This is where QEMU is going. There is no reason that a normal user > should ever use -nodefconfig. I don't think anyone or anything can use it, since it's meaning is not well defined. "not read any configuration files" where parts of qemu are continually moved out to configuration files means its a moving target. Suppose we define the southbridge via a configuration file. Does that mean we don't load it any more? -- error compiling committee.c: too many arguments to function -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/25/2012 04:59 PM, Anthony Liguori wrote: > On 03/25/2012 09:46 AM, Avi Kivity wrote: >> On 03/25/2012 04:36 PM, Anthony Liguori wrote: Apart from the command line length, it confuses configuration with definition. >>> >>> >>> There is no distinction with what we have today. Our configuration >>> file basically corresponds to command line options and as there is no >>> distinction in command line options, there's no distinction in the >>> configuration format. >> >> We don't have command line options for defining, only configuring. > > That's an oversight. There should be a -cpudef option. It's a > QemuOptsList. > >> Again, defining = #define > > I think -global fits your definition of #define... Yes (apart from the corner case of modifying a default-instantiated device). >>> B) A management tool has complete control over cpu definitions without >>> modifying the underlying filesystem. -nodefconfig will prevent it >>> from loading and the management tool can explicitly load the QEMU >>> definition (via -readconfig, potentially using a /dev/fd/N path) or it >>> can define it's own cpu definitions. >> >> Why does -nodefconfig affect anything? > > > Because -nodefconfig means "don't load *any* default configuration > files". Put the emphasis around *configuration*. "#define westmere blah" is not configuration, otherwise the meaning of configuration will drift over time. -cpu blah is, of course. > >> The file defines westmere as an alias for a grab bag of options. >> Whether it's loaded or not is immaterial, unless someone uses one of the >> names within. > > But you would agree, a management tool should be able to control > whether class factories get loaded, right? No, why? But perhaps I don't entirely get what you mean by "class factories". Aren't they just implementations of virtual Device *new_instance(...) = 0? if so, why not load them? > So what's the mechanism to do this? > >>> C) This model maps to any other type of class factory. Machines will >>> eventually be expressed as a class factory. When we implement this, >>> we would change the default target-x86_64-cpu.cfg to: >>> >>> [system] >>> # Load default CPU definitions >>> readconfig = @DATADIR@/target-x86_64-cpus.cfg >>> # Load default machines >>> readconfig = @DATADIR@/target-x86_64-machines.cfg >>> >>> A machine definition would look like: >>> >>> [machinedef] >>> name = pc-0.15 >>> virtio-blk.class_code = 32 >>> ... >>> >>> Loading a file based on -cpu doesn't generalize well unless we try to >>> load a definition for any possible QOM type to find the class factory >>> for it. I don't think this is a good idea. >> >> Why not load all class factories? Just don't instantiate any objects. > > Unless we have two different config syntaxes, I think it will lead to > a lot of confusion. Having some parts of a config file be parsed and > others not is fairly strange. Parse all of them (and make sure all are class factories). The only real configuration item is that without -nodefconfig, we create a -M pc-1.1 system. Everything else derives from that. > >> Otherwise, the meaning of -nodefconfig changes as more stuff is moved >> out of .c and into .cfg. > > What's the problem with this? The command line becomes unstable if you use -nodefconfig. >>> >>> In my target-$(ARCH).cfg, I have: >>> >>> [machine] >>> enable-kvm = "on" >>> >>> Which means I don't have to use -enable-kvm anymore. But if you look >>> at a tool like libguestfs, start up time is the most important thing >>> so avoiding unnecessary I/O and processing is critical. >> >> So this is definitely configuration (applies to the current instance) as >> opposed to target-x86_64.cfg, which doesn't. > > > I'm not sure which part you're responding to.. I was saying that target-x86_64.cfg appears to be definitions, not configuration, and was asking about qemu.cfg (which is configuration). >> As far as I can tell, the only difference is that -nodefconfig -cpu >> westmere will error out instead of working. But if you don't supply >> -cpu westmere, the configuration is identical. > > What configuration? > > Let me ask, what do you think the semantics of -nodefconfig should > be? I'm not sure I understand what you're advocating for. > -nodefconfig = create an empty machine, don't assume anything (=don't read qemu.cfg) let me build it out of all those lego bricks. Those can be defined in code or in definition files in /usr/share, I don't care. Maybe that's -nodevices -vga none. But in this case I don't see the point in -nodefconfig. Not loading target_x86-64.cfg doesn't buy the user anything, since it wouldn't affect the guest in any way. -- error compiling committee.c: too many arguments to function -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/25/2012 09:58 AM, Gleb Natapov wrote: On Sun, Mar 25, 2012 at 03:14:56PM +0200, Avi Kivity wrote: On 03/25/2012 03:12 PM, Anthony Liguori wrote: qemu -M pc Would effectively be short hand for -readconfig /usr/share/qemu/machines/pc.cfg In that case qemu -cpu westmere is shorthand for -readconfig /usr/share/qemu/cpus/westmere.cfg. This is not a bad suggestion, although it would make -cpu ? a bit awkward. Do you see an advantage to this over having /usr/share/qemu/target-x86_64-cpus.cfg that's read early on? Nope. As long as qemu -nodefconfig -cpu westmere works, I'm happy. As log as qemu -nodefconfig -cpu westmere -M pc1.1 -nodefconfig is going to eventually mean that -cpu westmere and -M pc-1.1 will not work. This is where QEMU is going. There is no reason that a normal user should ever use -nodefconfig. Regards, Anthony Liguori -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/25/2012 09:46 AM, Avi Kivity wrote:
On 03/25/2012 04:36 PM, Anthony Liguori wrote:
Apart from the command line length, it confuses configuration with
definition.
There is no distinction with what we have today. Our configuration
file basically corresponds to command line options and as there is no
distinction in command line options, there's no distinction in the
configuration format.
We don't have command line options for defining, only configuring.
That's an oversight. There should be a -cpudef option. It's a QemuOptsList.
Again, defining = #define
I think -global fits your definition of #define...
Configuring = modifying current instance
target-x86_64-cpus.cfg does not configure qemu for anything, it's merely
the equivalent of
#define westmere (x86_def_t) { ... }
#define nehalem (x86_def_t) { ... }
#define bulldozer (x86_def_t) { ... } // for PC
so it should be read at each invocation. On the other hand, pc.cfg and
westmere.cfg (as used previously) are shorthand for
machine = (QEMUMachine) { ... };
cpu = (x86_def_t) { ... };
so they should only be read if requested explicitly (or indirectly).
This doesn't make a lot of sense to me. Here's what I'm proposing:
1) QEMU would have a target-x86_64-cpu.cfg.in that is installed by
default in /etc/qemu. It would contain:
[system]
# Load default CPU definitions
readconfig = @DATADIR@/target-x86_64-cpus.cfg
2) target-x86_64-cpus.cfg would be installed to @DATADIR@ and would
contain:
[cpudef]
name = "Westmere"
...
This has the following properties:
A) QEMU has no builtin notion of CPU definitions. It just has a "cpu
factory". -cpudef will create a new class called Westmere that can
then be enumerated through qom-type-list and created via qom-create.
B) A management tool has complete control over cpu definitions without
modifying the underlying filesystem. -nodefconfig will prevent it
from loading and the management tool can explicitly load the QEMU
definition (via -readconfig, potentially using a /dev/fd/N path) or it
can define it's own cpu definitions.
Why does -nodefconfig affect anything?
Because -nodefconfig means "don't load *any* default configuration files".
The file defines westmere as an alias for a grab bag of options.
Whether it's loaded or not is immaterial, unless someone uses one of the
names within.
But you would agree, a management tool should be able to control whether class
factories get loaded, right? So what's the mechanism to do this?
C) This model maps to any other type of class factory. Machines will
eventually be expressed as a class factory. When we implement this,
we would change the default target-x86_64-cpu.cfg to:
[system]
# Load default CPU definitions
readconfig = @DATADIR@/target-x86_64-cpus.cfg
# Load default machines
readconfig = @DATADIR@/target-x86_64-machines.cfg
A machine definition would look like:
[machinedef]
name = pc-0.15
virtio-blk.class_code = 32
...
Loading a file based on -cpu doesn't generalize well unless we try to
load a definition for any possible QOM type to find the class factory
for it. I don't think this is a good idea.
Why not load all class factories? Just don't instantiate any objects.
Unless we have two different config syntaxes, I think it will lead to a lot of
confusion. Having some parts of a config file be parsed and others not is
fairly strange.
Otherwise, the meaning of -nodefconfig changes as more stuff is moved
out of .c and into .cfg.
What's the problem with this?
The reasoning is, loading target-x86_64-cpus.cfg does not alter the
current instance's configuration, so reading it doesn't violate
-nodefconfig.
I think we have a different view of what -nodefconfig does.
We have a couple options today:
-nodefconfig
Don't read the default configuration files. By default, we read
/etc/qemu/qemu.cfg and /etc/qemu/target-$(ARCH).cfg
The latter seems meaningless to avoid reading. It's just a set of
#defines, what do you get by not reading it?
In my target-$(ARCH).cfg, I have:
[machine]
enable-kvm = "on"
Which means I don't have to use -enable-kvm anymore. But if you look
at a tool like libguestfs, start up time is the most important thing
so avoiding unnecessary I/O and processing is critical.
So this is definitely configuration (applies to the current instance) as
opposed to target-x86_64.cfg, which doesn't.
I'm not sure which part you're responding to..
-nodefaults
Don't create default devices.
-vga none
Don't create the default VGA device (not covered by -nodefaults).
With these two options, the semantics you get an absolutely
minimalistic instance of QEMU. Tools like libguestfs really want to
create the simplest guest and do the least amount of processing so the
guest runs as fast as possible.
It does suck a lot that this isn't a single option. I would much
prefer -nodefaults to be implied by -nodefconfig. Likewise, I would
prefer that -nodefaults implied -
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Sun, Mar 25, 2012 at 03:14:56PM +0200, Avi Kivity wrote: > On 03/25/2012 03:12 PM, Anthony Liguori wrote: > >>> qemu -M pc > >>> > >>> Would effectively be short hand for -readconfig > >>> /usr/share/qemu/machines/pc.cfg > >> > >> In that case > >> > >> qemu -cpu westmere > >> > >> is shorthand for -readconfig /usr/share/qemu/cpus/westmere.cfg. > > > > > > This is not a bad suggestion, although it would make -cpu ? a bit > > awkward. Do you see an advantage to this over having > > /usr/share/qemu/target-x86_64-cpus.cfg that's read early on? > > Nope. As long as qemu -nodefconfig -cpu westmere works, I'm happy. > As log as qemu -nodefconfig -cpu westmere -M pc1.1 can use different westmere definition than -M pc1.0 (by amending it according to qom properties in pc1.1 machine description or by reading /usr/share/qemu/cpus/westmere-pc1.1.cfg instead) I'm happy too. > The reasoning is, loading target-x86_64-cpus.cfg does not alter the > current instance's configuration, so reading it doesn't violate > -nodefconfig. > > >>> files be read by default or just treated as additional configuration > >>> files. > >> > >> If they're read as soon as they're referenced, what's the difference? > > I think the thread has reduced to: should /usr/share configuration > > > > I suspect libvirt would not be happy with reading configuration files > > on demand.. > > Why not? > > -- > error compiling committee.c: too many arguments to function -- Gleb. -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/25/2012 04:36 PM, Anthony Liguori wrote:
>> Apart from the command line length, it confuses configuration with
>> definition.
>
>
> There is no distinction with what we have today. Our configuration
> file basically corresponds to command line options and as there is no
> distinction in command line options, there's no distinction in the
> configuration format.
We don't have command line options for defining, only configuring.
Again, defining = #define
Configuring = modifying current instance
>
>> target-x86_64-cpus.cfg does not configure qemu for anything, it's merely
>> the equivalent of
>>
>>#define westmere (x86_def_t) { ... }
>>#define nehalem (x86_def_t) { ... }
>>#define bulldozer (x86_def_t) { ... } // for PC
>>
>> so it should be read at each invocation. On the other hand, pc.cfg and
>> westmere.cfg (as used previously) are shorthand for
>>
>> machine = (QEMUMachine) { ... };
>> cpu = (x86_def_t) { ... };
>>
>> so they should only be read if requested explicitly (or indirectly).
>
> This doesn't make a lot of sense to me. Here's what I'm proposing:
>
> 1) QEMU would have a target-x86_64-cpu.cfg.in that is installed by
> default in /etc/qemu. It would contain:
>
> [system]
> # Load default CPU definitions
> readconfig = @DATADIR@/target-x86_64-cpus.cfg
>
> 2) target-x86_64-cpus.cfg would be installed to @DATADIR@ and would
> contain:
>
> [cpudef]
> name = "Westmere"
> ...
>
> This has the following properties:
>
> A) QEMU has no builtin notion of CPU definitions. It just has a "cpu
> factory". -cpudef will create a new class called Westmere that can
> then be enumerated through qom-type-list and created via qom-create.
>
> B) A management tool has complete control over cpu definitions without
> modifying the underlying filesystem. -nodefconfig will prevent it
> from loading and the management tool can explicitly load the QEMU
> definition (via -readconfig, potentially using a /dev/fd/N path) or it
> can define it's own cpu definitions.
Why does -nodefconfig affect anything?
The file defines westmere as an alias for a grab bag of options.
Whether it's loaded or not is immaterial, unless someone uses one of the
names within.
>
> C) This model maps to any other type of class factory. Machines will
> eventually be expressed as a class factory. When we implement this,
> we would change the default target-x86_64-cpu.cfg to:
>
> [system]
> # Load default CPU definitions
> readconfig = @DATADIR@/target-x86_64-cpus.cfg
> # Load default machines
> readconfig = @DATADIR@/target-x86_64-machines.cfg
>
> A machine definition would look like:
>
> [machinedef]
> name = pc-0.15
> virtio-blk.class_code = 32
> ...
>
> Loading a file based on -cpu doesn't generalize well unless we try to
> load a definition for any possible QOM type to find the class factory
> for it. I don't think this is a good idea.
Why not load all class factories? Just don't instantiate any objects.
Otherwise, the meaning of -nodefconfig changes as more stuff is moved
out of .c and into .cfg.
>
The reasoning is, loading target-x86_64-cpus.cfg does not alter the
current instance's configuration, so reading it doesn't violate
-nodefconfig.
>>>
>>> I think we have a different view of what -nodefconfig does.
>>>
>>> We have a couple options today:
>>>
>>> -nodefconfig
>>>
>>> Don't read the default configuration files. By default, we read
>>> /etc/qemu/qemu.cfg and /etc/qemu/target-$(ARCH).cfg
>>>
>>
>> The latter seems meaningless to avoid reading. It's just a set of
>> #defines, what do you get by not reading it?
>
> In my target-$(ARCH).cfg, I have:
>
> [machine]
> enable-kvm = "on"
>
> Which means I don't have to use -enable-kvm anymore. But if you look
> at a tool like libguestfs, start up time is the most important thing
> so avoiding unnecessary I/O and processing is critical.
So this is definitely configuration (applies to the current instance) as
opposed to target-x86_64.cfg, which doesn't.
>
>>> -nodefaults
>>>
>>> Don't create default devices.
>>>
>>> -vga none
>>>
>>> Don't create the default VGA device (not covered by -nodefaults).
>>>
>>> With these two options, the semantics you get an absolutely
>>> minimalistic instance of QEMU. Tools like libguestfs really want to
>>> create the simplest guest and do the least amount of processing so the
>>> guest runs as fast as possible.
>>>
>>> It does suck a lot that this isn't a single option. I would much
>>> prefer -nodefaults to be implied by -nodefconfig. Likewise, I would
>>> prefer that -nodefaults implied -vga none.
>>
>> I don't have a qemu.cfg so can't comment on it, but in what way does
>> reading target-x86_64.cfg affect the current instance (that is, why is
>> -nodefconfig needed over -nodefaults -vga look-at-the-previous-option?)
>
> It depends on what the user configures it to do.
How?
As far as I can tell, the only difference is that -nodefconfig -cpu
westmere will error out instead of working. But if
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/25/2012 08:34 AM, Avi Kivity wrote:
On 03/25/2012 03:22 PM, Anthony Liguori wrote:
In that case
qemu -cpu westmere
is shorthand for -readconfig /usr/share/qemu/cpus/westmere.cfg.
This is not a bad suggestion, although it would make -cpu ? a bit
awkward. Do you see an advantage to this over having
/usr/share/qemu/target-x86_64-cpus.cfg that's read early on?
Nope. As long as qemu -nodefconfig -cpu westmere works, I'm happy.
Why? What's wrong with:
qemu -nodefconfig -readconfig
/usr/share/qemu/cpus/target-x86_64-cpus.cfg \
-cpu westmere
And if that's not okay, would:
qemu -nodefconfig -nocpudefconfig -cpu Westmere
Not working be a problem?
Apart from the command line length, it confuses configuration with
definition.
There is no distinction with what we have today. Our configuration file
basically corresponds to command line options and as there is no distinction in
command line options, there's no distinction in the configuration format.
target-x86_64-cpus.cfg does not configure qemu for anything, it's merely
the equivalent of
#define westmere (x86_def_t) { ... }
#define nehalem (x86_def_t) { ... }
#define bulldozer (x86_def_t) { ... } // for PC
so it should be read at each invocation. On the other hand, pc.cfg and
westmere.cfg (as used previously) are shorthand for
machine = (QEMUMachine) { ... };
cpu = (x86_def_t) { ... };
so they should only be read if requested explicitly (or indirectly).
This doesn't make a lot of sense to me. Here's what I'm proposing:
1) QEMU would have a target-x86_64-cpu.cfg.in that is installed by default in
/etc/qemu. It would contain:
[system]
# Load default CPU definitions
readconfig = @DATADIR@/target-x86_64-cpus.cfg
2) target-x86_64-cpus.cfg would be installed to @DATADIR@ and would contain:
[cpudef]
name = "Westmere"
...
This has the following properties:
A) QEMU has no builtin notion of CPU definitions. It just has a "cpu factory".
-cpudef will create a new class called Westmere that can then be enumerated
through qom-type-list and created via qom-create.
B) A management tool has complete control over cpu definitions without modifying
the underlying filesystem. -nodefconfig will prevent it from loading and the
management tool can explicitly load the QEMU definition (via -readconfig,
potentially using a /dev/fd/N path) or it can define it's own cpu definitions.
C) This model maps to any other type of class factory. Machines will eventually
be expressed as a class factory. When we implement this, we would change the
default target-x86_64-cpu.cfg to:
[system]
# Load default CPU definitions
readconfig = @DATADIR@/target-x86_64-cpus.cfg
# Load default machines
readconfig = @DATADIR@/target-x86_64-machines.cfg
A machine definition would look like:
[machinedef]
name = pc-0.15
virtio-blk.class_code = 32
...
Loading a file based on -cpu doesn't generalize well unless we try to load a
definition for any possible QOM type to find the class factory for it. I don't
think this is a good idea.
The reasoning is, loading target-x86_64-cpus.cfg does not alter the
current instance's configuration, so reading it doesn't violate
-nodefconfig.
I think we have a different view of what -nodefconfig does.
We have a couple options today:
-nodefconfig
Don't read the default configuration files. By default, we read
/etc/qemu/qemu.cfg and /etc/qemu/target-$(ARCH).cfg
The latter seems meaningless to avoid reading. It's just a set of
#defines, what do you get by not reading it?
In my target-$(ARCH).cfg, I have:
[machine]
enable-kvm = "on"
Which means I don't have to use -enable-kvm anymore. But if you look at a tool
like libguestfs, start up time is the most important thing so avoiding
unnecessary I/O and processing is critical.
-nodefaults
Don't create default devices.
-vga none
Don't create the default VGA device (not covered by -nodefaults).
With these two options, the semantics you get an absolutely
minimalistic instance of QEMU. Tools like libguestfs really want to
create the simplest guest and do the least amount of processing so the
guest runs as fast as possible.
It does suck a lot that this isn't a single option. I would much
prefer -nodefaults to be implied by -nodefconfig. Likewise, I would
prefer that -nodefaults implied -vga none.
I don't have a qemu.cfg so can't comment on it, but in what way does
reading target-x86_64.cfg affect the current instance (that is, why is
-nodefconfig needed over -nodefaults -vga look-at-the-previous-option?)
It depends on what the user configures it to do.
Regards,
Anthony Liguori
--
libvir-list mailing list
libvir-list@redhat.com
https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/25/2012 03:22 PM, Anthony Liguori wrote:
In that case
qemu -cpu westmere
is shorthand for -readconfig /usr/share/qemu/cpus/westmere.cfg.
>>>
>>>
>>> This is not a bad suggestion, although it would make -cpu ? a bit
>>> awkward. Do you see an advantage to this over having
>>> /usr/share/qemu/target-x86_64-cpus.cfg that's read early on?
>>
>> Nope. As long as qemu -nodefconfig -cpu westmere works, I'm happy.
>
>
> Why? What's wrong with:
>
> qemu -nodefconfig -readconfig
> /usr/share/qemu/cpus/target-x86_64-cpus.cfg \
> -cpu westmere
>
> And if that's not okay, would:
>
> qemu -nodefconfig -nocpudefconfig -cpu Westmere
>
> Not working be a problem?
Apart from the command line length, it confuses configuration with
definition.
target-x86_64-cpus.cfg does not configure qemu for anything, it's merely
the equivalent of
#define westmere (x86_def_t) { ... }
#define nehalem (x86_def_t) { ... }
#define bulldozer (x86_def_t) { ... } // for PC
so it should be read at each invocation. On the other hand, pc.cfg and
westmere.cfg (as used previously) are shorthand for
machine = (QEMUMachine) { ... };
cpu = (x86_def_t) { ... };
so they should only be read if requested explicitly (or indirectly).
>
>> The reasoning is, loading target-x86_64-cpus.cfg does not alter the
>> current instance's configuration, so reading it doesn't violate
>> -nodefconfig.
>
> I think we have a different view of what -nodefconfig does.
>
> We have a couple options today:
>
> -nodefconfig
>
> Don't read the default configuration files. By default, we read
> /etc/qemu/qemu.cfg and /etc/qemu/target-$(ARCH).cfg
>
The latter seems meaningless to avoid reading. It's just a set of
#defines, what do you get by not reading it?
> -nodefaults
>
> Don't create default devices.
>
> -vga none
>
> Don't create the default VGA device (not covered by -nodefaults).
>
> With these two options, the semantics you get an absolutely
> minimalistic instance of QEMU. Tools like libguestfs really want to
> create the simplest guest and do the least amount of processing so the
> guest runs as fast as possible.
>
> It does suck a lot that this isn't a single option. I would much
> prefer -nodefaults to be implied by -nodefconfig. Likewise, I would
> prefer that -nodefaults implied -vga none.
I don't have a qemu.cfg so can't comment on it, but in what way does
reading target-x86_64.cfg affect the current instance (that is, why is
-nodefconfig needed over -nodefaults -vga look-at-the-previous-option?)
>
> files be read by default or just treated as additional configuration
> files.
If they're read as soon as they're referenced, what's the difference?
>>> I think the thread has reduced to: should /usr/share configuration
>>>
>>> I suspect libvirt would not be happy with reading configuration files
>>> on demand..
>>
>> Why not?
>
> It implies a bunch of SELinux labeling to make sVirt work. libvirt
> tries very hard to avoid having QEMU read *any* files at all when it
> starts up.
The /usr/share/qemu files should be statically labelled to allow qemu to
read them, so we can push more code into data files.
--
error compiling committee.c: too many arguments to function
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Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/25/2012 08:21 AM, Avi Kivity wrote: On 03/11/2012 04:12 PM, Anthony Liguori wrote: This discussion isn't about whether QEMU should have a Westmere processor definition. In fact, I think I already applied that patch. It's a discussion about how we handle this up and down the stack. The question is who should define and manage CPU compatibility. Right now QEMU does to a certain degree, libvirt discards this and does it's own thing, and VDSM/ovirt-engine assume that we're providing something and has built a UI around it. What I'm proposing we consider: have VDSM manage CPU definitions in order to provide a specific user experience in ovirt-engine. We would continue to have Westmere/etc in QEMU exposed as part of the user configuration. But I don't think it makes a lot of sense to have to modify QEMU any time a new CPU comes out. We have to. New features often come with new MSRs which need to be live migrated, and of course the cpu flags as well. We may push all these to qemu data files, but this is still qemu. We can't let a management tool decide that cpu feature X is safe to use on qemu version Y. I think QEMU should own CPU definitions. I think a management tool should have the choice of whether they are used though because they are a policy IMHO. It's okay for QEMU to implement some degree of policy as long as a management tool can override it with a different policy. Regards, Anthony Liguori -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/25/2012 08:14 AM, Avi Kivity wrote: On 03/25/2012 03:12 PM, Anthony Liguori wrote: qemu -M pc Would effectively be short hand for -readconfig /usr/share/qemu/machines/pc.cfg In that case qemu -cpu westmere is shorthand for -readconfig /usr/share/qemu/cpus/westmere.cfg. This is not a bad suggestion, although it would make -cpu ? a bit awkward. Do you see an advantage to this over having /usr/share/qemu/target-x86_64-cpus.cfg that's read early on? Nope. As long as qemu -nodefconfig -cpu westmere works, I'm happy. Why? What's wrong with: qemu -nodefconfig -readconfig /usr/share/qemu/cpus/target-x86_64-cpus.cfg \ -cpu westmere And if that's not okay, would: qemu -nodefconfig -nocpudefconfig -cpu Westmere Not working be a problem? The reasoning is, loading target-x86_64-cpus.cfg does not alter the current instance's configuration, so reading it doesn't violate -nodefconfig. I think we have a different view of what -nodefconfig does. We have a couple options today: -nodefconfig Don't read the default configuration files. By default, we read /etc/qemu/qemu.cfg and /etc/qemu/target-$(ARCH).cfg -nodefaults Don't create default devices. -vga none Don't create the default VGA device (not covered by -nodefaults). With these two options, the semantics you get an absolutely minimalistic instance of QEMU. Tools like libguestfs really want to create the simplest guest and do the least amount of processing so the guest runs as fast as possible. It does suck a lot that this isn't a single option. I would much prefer -nodefaults to be implied by -nodefconfig. Likewise, I would prefer that -nodefaults implied -vga none. files be read by default or just treated as additional configuration files. If they're read as soon as they're referenced, what's the difference? I think the thread has reduced to: should /usr/share configuration I suspect libvirt would not be happy with reading configuration files on demand.. Why not? It implies a bunch of SELinux labeling to make sVirt work. libvirt tries very hard to avoid having QEMU read *any* files at all when it starts up. Regards, Anthony Liguori -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/11/2012 04:12 PM, Anthony Liguori wrote: >> Let me elaborate about the later. Suppose host CPU has kill_guest >> feature and at the time a guest was installed it was not implemented by >> kvm. Since it was not implemented by kvm it was not present in vcpu >> during installation and the guest didn't install "workaround kill_guest" >> module. Now unsuspecting user upgrades the kernel and tries to restart >> the guest and fails. He writes angry letter to qemu-devel and is >> asked to >> reinstall his guest and move along. > > > -cpu best wouldn't solve this. You need a read/write configuration > file where QEMU probes the available CPU and records it to be used for > the lifetime of the VM. This doesn't work with live migration, and makes templating harder. The only persistent storage we can count on are disk images. The current approach is simple. The management tool determines the configuration, qemu applies it. Unidirectional information flow. This also lends itself to the management tool scanning a cluster and determining a GCD. > This discussion isn't about whether QEMU should have a Westmere > processor definition. In fact, I think I already applied that patch. > > It's a discussion about how we handle this up and down the stack. > > The question is who should define and manage CPU compatibility. Right > now QEMU does to a certain degree, libvirt discards this and does it's > own thing, and VDSM/ovirt-engine assume that we're providing something > and has built a UI around it. > > What I'm proposing we consider: have VDSM manage CPU definitions in > order to provide a specific user experience in ovirt-engine. > > We would continue to have Westmere/etc in QEMU exposed as part of the > user configuration. But I don't think it makes a lot of sense to have > to modify QEMU any time a new CPU comes out. We have to. New features often come with new MSRs which need to be live migrated, and of course the cpu flags as well. We may push all these to qemu data files, but this is still qemu. We can't let a management tool decide that cpu feature X is safe to use on qemu version Y. -- error compiling committee.c: too many arguments to function -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/25/2012 03:12 PM, Anthony Liguori wrote: >>> qemu -M pc >>> >>> Would effectively be short hand for -readconfig >>> /usr/share/qemu/machines/pc.cfg >> >> In that case >> >> qemu -cpu westmere >> >> is shorthand for -readconfig /usr/share/qemu/cpus/westmere.cfg. > > > This is not a bad suggestion, although it would make -cpu ? a bit > awkward. Do you see an advantage to this over having > /usr/share/qemu/target-x86_64-cpus.cfg that's read early on? Nope. As long as qemu -nodefconfig -cpu westmere works, I'm happy. The reasoning is, loading target-x86_64-cpus.cfg does not alter the current instance's configuration, so reading it doesn't violate -nodefconfig. >>> files be read by default or just treated as additional configuration >>> files. >> >> If they're read as soon as they're referenced, what's the difference? > I think the thread has reduced to: should /usr/share configuration > > I suspect libvirt would not be happy with reading configuration files > on demand.. Why not? -- error compiling committee.c: too many arguments to function -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/25/2012 08:08 AM, Avi Kivity wrote: On 03/25/2012 02:55 PM, Anthony Liguori wrote: If cpu models are not part of configuration they should not be affected by configuration mechanism. You are just avoiding addressing the real question that if asked above. I think you're just refusing to listen. The stated direction of QEMU, for literally years now, is that we want to arrive at the following: QEMU is composed of a series of objects who's relationships can be fully described by an external configuration file. Much of the current baked in concepts (like machines) would then become configuration files. qemu -M pc Would effectively be short hand for -readconfig /usr/share/qemu/machines/pc.cfg In that case qemu -cpu westmere is shorthand for -readconfig /usr/share/qemu/cpus/westmere.cfg. This is not a bad suggestion, although it would make -cpu ? a bit awkward. Do you see an advantage to this over having /usr/share/qemu/target-x86_64-cpus.cfg that's read early on? I think the thread has reduced to: should /usr/share configuration files be read by default or just treated as additional configuration files. If they're read as soon as they're referenced, what's the difference? I suspect libvirt would not be happy with reading configuration files on demand.. Regards, Anthony Liguori -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/25/2012 02:55 PM, Anthony Liguori wrote: >> If cpu models are not part of configuration they should not be affected >> by configuration mechanism. You are just avoiding addressing the real >> question that if asked above. > > > I think you're just refusing to listen. > > The stated direction of QEMU, for literally years now, is that we want > to arrive at the following: > > QEMU is composed of a series of objects who's relationships can be > fully described by an external configuration file. Much of the > current baked in concepts (like machines) would then become > configuration files. > > qemu -M pc > > Would effectively be short hand for -readconfig > /usr/share/qemu/machines/pc.cfg In that case qemu -cpu westmere is shorthand for -readconfig /usr/share/qemu/cpus/westmere.cfg. > I think the thread has reduced to: should /usr/share configuration > files be read by default or just treated as additional configuration > files. If they're read as soon as they're referenced, what's the difference? -- error compiling committee.c: too many arguments to function -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/25/2012 04:49 AM, Gleb Natapov wrote: On Thu, Mar 22, 2012 at 03:01:17PM -0500, Anthony Liguori wrote: So let's avoid that and start by having a positive configuration mechanism that the user can use to change the path and exclude it. My suggestion eliminate the need for two future command line options. If cpu models are not part of configuration they should not be affected by configuration mechanism. You are just avoiding addressing the real question that if asked above. I think you're just refusing to listen. The stated direction of QEMU, for literally years now, is that we want to arrive at the following: QEMU is composed of a series of objects who's relationships can be fully described by an external configuration file. Much of the current baked in concepts (like machines) would then become configuration files. qemu -M pc Would effectively be short hand for -readconfig /usr/share/qemu/machines/pc.cfg There are some valid points that were raised in this thread, namely that the user needs to have a file that acts as strictly config (stored in /etc). I'm totally happy moving the CPU configuration to /usr/share in order to address this. I think the thread has reduced to: should /usr/share configuration files be read by default or just treated as additional configuration files. It seems pretty obvious to me that they should be treated as normal configuration files. This gives you the user the ability to have fine grain control over which files are used including the ability to change the location for each file. Maybe RHEL only wants to expose supported CPUs and supported machines, wouldn't it be better to not have to patch QEMU to do that? Wouldn't it be even better if you could drop in a separate CPU configuration file with the supported CPU types and then change the default /etc config to use that instead? Regards, Anthony Liguori -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Thu, Mar 22, 2012 at 12:50:18PM -0300, Eduardo Habkost wrote: > On Thu, Mar 22, 2012 at 04:30:55PM +0200, Gleb Natapov wrote: > > On Thu, Mar 22, 2012 at 10:31:21AM -0300, Eduardo Habkost wrote: > > > On Thu, Mar 22, 2012 at 11:32:44AM +0200, Gleb Natapov wrote: > > > > What does this mean? Will -nodefconfig disable loading of bios.bin, > > > > option roms, keymaps? > > > > > > Correcting myself: loading of _config_ files on /usr/share. ROM images > > > are opaque data to be presented to the guest somehow, just like a disk > > > image or kernel binary. But maybe keymaps will become "configuration" > > > someday, I really don't know. > > > > > Where do you draw the line between "opaque data" and configuration. CPU > > models are also something that is present to a guest somehow. > > Just the fact that it's in a structured key=value format that Qemu > itself will interpret before exposing something to the guest. Yes, it's > a bit arbitrary. If we could make everything "configuration data", we > would (or that's what I think Anthony is pushing for--I hope he will > reply and clarify that). > It is not a "bit arbitrary" it is completely arbitrary. > > Are you > > consider ROMs to be "opaque data" because they are binary and CPU models > > to be config just because it is ascii file? > > Not just "ascii file", but structured (and relatively small) > [section]key=value data. If BIOSes were not opaque binary code and could > be converted to a small set of config sections and key=values just like > cpudefs, one could argue that BIOSes could become configuration data, > too. > There is no argument I can make about it since there is no logic to refute to begin with :) Well may be except that when cpu model file will support configuring all couid leafs for each cpu model it will not be so small :) > > > What if we pre-process CPU > > models into binary for QEMU to read will it magically stop being > > configuration? > > Doing the reverse (transforming simple [section]key=value data to a > binary format) would just be silly and wouldn't gain us anything. The > point here is that we (Qemu) seem to be moving towards a design where > most things are structured "configuration data" that fits on a > [section]key=value model, and Qemu just interprets that structured data > to build a virtual machine. Nothing silly about it. You can move data parsing outside of QEMU and just mmap cpu definitions in QEMU. > > (That's why I said that perhaps keymaps could become configuration > someday. Because maybe they can be converted to a key=value model > relatively easily) > Such whole sale approach is harmful since it starts to affect design decisions. So now if it seams logical to move something outside the code one can decide against it just because it will become "configuration" due to that design. > > > > > > > Doing this would make it impossible to deploy fixes to users if we > > > > > > evern > > > > > > find out that the default configuration file had a serious bug. > > > > > > What if > > > > > > a bug in our default configuration file has a serious security > > > > > > implication? > > > > > > > > > > The answer to this is: if the broken templates/defaults are on > > > > > /usr/share, it would be easy to deploy the fix. > > > > > > > > > > So, the compromise solution is: > > > > > > > > > > - We can move some configuration data (especially defaults/templates) > > > > > to /usr/share (machine-types and CPU models could go there). This > > > > > way we can easily deploy fixes to the defaults, if necessary. > > > > > - To reuse Qemu models, or machine-types, and not define everything > > > > > from > > > > > scratch, libvirt will have to use something like: > > > > > "-nodefconfig -readconfig /usr/share/qemu/cpu-models-x86.conf" > > > > > > > > > cpu-models-x86.conf is not a configuration file. It is hardware > > > > description file. QEMU should not lose capability just because you run > > > > it with -nodefconfig. -nodefconfig means that QEMU does not create > > > > machine for you, but all parts needed to create a machine that would > > > > have > > > > been created without -nodefconfig are still present. Not been able to > > > > create Nehalem CPU after specifying -nodefconfig is the same as not been > > > > able to create virtio-net i.e the bug. > > > > > > > > > The current design direction Qemu seems to be following is different > > > from that: hardware description is also considered "configuration" just > > > like actual machine configuration. Anthony, please correct me if I am > > > wrong. > > That's a bug. Why trying to rationalize it now instead of fixing it. > > It's just a bug for you because you disagree with the current design. > You can call it rationalization, yes; I am just accepting Anthony's > proposal because it's equally good (to me) as what you are proposing. > > > > It > > was fixed in RHEL by the same person who introduced it in upstream in > > the first place. He j
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Thu, Mar 22, 2012 at 03:01:17PM -0500, Anthony Liguori wrote: > On 03/22/2012 12:14 PM, Eduardo Habkost wrote: > >On Thu, Mar 22, 2012 at 11:37:39AM -0500, Anthony Liguori wrote: > >>On 03/22/2012 04:32 AM, Gleb Natapov wrote: > >>>On Tue, Mar 13, 2012 at 11:53:19AM -0300, Eduardo Habkost wrote: > So, this problem is solved if the defaults are easily found on > /usr/share. > > >>>What problem is solved and why are we mixing machine configuration files > >>>and cpu configuration files? They are different and should be treated > >>>differently. -nodefconfig exists only because there is not machine > >>>configuration files currently. With machine configuration files > >>>libvirt does not need -nodefconfig because it can create its own machine > >>>file and make QEMU use it. So specifying machine file on QEMU's command > >>>line implies -nodefconfig. The option itself loses its meaning and can be > >>>dropped. > >> > >>No, -nodefconfig means "no default config". > >> > >>As with many projects, we can have *some* configuration required. > >> > >>The default configure should have a: > >> > >>[system] > >>readconfig=@SYSCONFDIR@/cpu-models-x86_64.cfg > > > >Not @SYSCONFDIR@, but @DATADIR@. CPU models belong to /usr/share because > >they aren't meant to be changed by the user (I think I already explained > >why: because we have to be able to deploy fixes to them). > > > >> > >>Stanza by default. If libvirt wants to reuse this, they can use > >>-readconfig if they use -nodefconfig. > > > >You are just repeating how you believe it should work based on the > >premise that "cpudefs are configuration". We're discussing/questioning > >this exact premise, here, and I would really appreciate to hear why the > >model Gleb is proposing is not valid. > > > >More precisely, this part: > > > >>>cpu-models-x86.conf is not a configuration file. It is hardware > >>>description file. QEMU should not lose capability just because you run > >>>it with -nodefconfig. -nodefconfig means that QEMU does not create > >>>machine for you, but all parts needed to create a machine that would have > >>>been created without -nodefconfig are still present. Not been able to > >>>create Nehalem CPU after specifying -nodefconfig is the same as not been > >>>able to create virtio-net i.e the bug. > > > >And the related points Gleb mentioned further in this thread. > > Because the next patch series that would follow would be a > -cpu-defs-path that would be a one-off hack with a global variable > and a -no-cpu-defs. > And it will be rejected since cpu models are not part of configuration, but QEMU internals stored in outside file. We have -L switch to tell qemu where such things should be loaded from and that's it. > So let's avoid that and start by having a positive configuration > mechanism that the user can use to change the path and exclude it. > My suggestion eliminate the need for two future command line > options. > If cpu models are not part of configuration they should not be affected by configuration mechanism. You are just avoiding addressing the real question that if asked above. -- Gleb. -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/22/2012 12:14 PM, Eduardo Habkost wrote: On Thu, Mar 22, 2012 at 11:37:39AM -0500, Anthony Liguori wrote: On 03/22/2012 04:32 AM, Gleb Natapov wrote: On Tue, Mar 13, 2012 at 11:53:19AM -0300, Eduardo Habkost wrote: So, this problem is solved if the defaults are easily found on /usr/share. What problem is solved and why are we mixing machine configuration files and cpu configuration files? They are different and should be treated differently. -nodefconfig exists only because there is not machine configuration files currently. With machine configuration files libvirt does not need -nodefconfig because it can create its own machine file and make QEMU use it. So specifying machine file on QEMU's command line implies -nodefconfig. The option itself loses its meaning and can be dropped. No, -nodefconfig means "no default config". As with many projects, we can have *some* configuration required. The default configure should have a: [system] readconfig=@SYSCONFDIR@/cpu-models-x86_64.cfg Not @SYSCONFDIR@, but @DATADIR@. CPU models belong to /usr/share because they aren't meant to be changed by the user (I think I already explained why: because we have to be able to deploy fixes to them). Stanza by default. If libvirt wants to reuse this, they can use -readconfig if they use -nodefconfig. You are just repeating how you believe it should work based on the premise that "cpudefs are configuration". We're discussing/questioning this exact premise, here, and I would really appreciate to hear why the model Gleb is proposing is not valid. More precisely, this part: cpu-models-x86.conf is not a configuration file. It is hardware description file. QEMU should not lose capability just because you run it with -nodefconfig. -nodefconfig means that QEMU does not create machine for you, but all parts needed to create a machine that would have been created without -nodefconfig are still present. Not been able to create Nehalem CPU after specifying -nodefconfig is the same as not been able to create virtio-net i.e the bug. And the related points Gleb mentioned further in this thread. Because the next patch series that would follow would be a -cpu-defs-path that would be a one-off hack with a global variable and a -no-cpu-defs. So let's avoid that and start by having a positive configuration mechanism that the user can use to change the path and exclude it. My suggestion eliminate the need for two future command line options. Regards, Anthony Liguori -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Thu, Mar 22, 2012 at 11:37:39AM -0500, Anthony Liguori wrote: > On 03/22/2012 04:32 AM, Gleb Natapov wrote: > >On Tue, Mar 13, 2012 at 11:53:19AM -0300, Eduardo Habkost wrote: > >>So, this problem is solved if the defaults are easily found on > >>/usr/share. > >> > >What problem is solved and why are we mixing machine configuration files > >and cpu configuration files? They are different and should be treated > >differently. -nodefconfig exists only because there is not machine > >configuration files currently. With machine configuration files > >libvirt does not need -nodefconfig because it can create its own machine > >file and make QEMU use it. So specifying machine file on QEMU's command > >line implies -nodefconfig. The option itself loses its meaning and can be > >dropped. > > No, -nodefconfig means "no default config". > > As with many projects, we can have *some* configuration required. > > The default configure should have a: > > [system] > readconfig=@SYSCONFDIR@/cpu-models-x86_64.cfg Not @SYSCONFDIR@, but @DATADIR@. CPU models belong to /usr/share because they aren't meant to be changed by the user (I think I already explained why: because we have to be able to deploy fixes to them). > > Stanza by default. If libvirt wants to reuse this, they can use > -readconfig if they use -nodefconfig. You are just repeating how you believe it should work based on the premise that "cpudefs are configuration". We're discussing/questioning this exact premise, here, and I would really appreciate to hear why the model Gleb is proposing is not valid. More precisely, this part: > >cpu-models-x86.conf is not a configuration file. It is hardware > >description file. QEMU should not lose capability just because you run > >it with -nodefconfig. -nodefconfig means that QEMU does not create > >machine for you, but all parts needed to create a machine that would have > >been created without -nodefconfig are still present. Not been able to > >create Nehalem CPU after specifying -nodefconfig is the same as not been > >able to create virtio-net i.e the bug. And the related points Gleb mentioned further in this thread. -- Eduardo -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/22/2012 04:32 AM, Gleb Natapov wrote: On Tue, Mar 13, 2012 at 11:53:19AM -0300, Eduardo Habkost wrote: So, trying to summarize what was discussed in the call: On Mon, Mar 12, 2012 at 10:08:10AM -0300, Eduardo Habkost wrote: Let's say we moved CPU definitions to /usr/share/qemu/cpu-models.xml. Obviously, we'd want a command line option to be able to change that location so we'd introduce -cpu-models PATH. But we want all of our command line options to be settable by the global configuration file so we would have a cpu-model=PATH to the configuration file. But why hard code a path when we can just set the default path in the configuration file so let's avoid hard coding and just put cpu-models=/usr/share/qemu/cpu-models.xml in the default configuration file. We wouldn't do the above. -nodefconfig should disable the loading of files on /etc, but it shouldn't disable loading internal non-configurable data that we just happened to choose to store outside the qemu binary because it makes development easier. The statement above is the one not fulfilled by the compromise solution: -nodefconfig would really disable the loading of files on /usr/share. What does this mean? Will -nodefconfig disable loading of bios.bin, option roms, keymaps? Really, the requirement of a "default configuration file" is a problem by itself. Qemu should not require a default configuration file to work, and it shouldn't require users to copy the default configuration file to change options from the default. The statement above is only partly true. The default configuration file would be still needed, but if defaults are stored on /usr/share, I will be happy with it. My main problem was with the need to _copy_ or edit a non-trivial default config file. If the not-often-edited defaults/templates are easily found on /usr/share to be used with -readconfig, I will be happy with this solution, even if -nodefconfig disable the files on /usr/share. Doing this would make it impossible to deploy fixes to users if we evern find out that the default configuration file had a serious bug. What if a bug in our default configuration file has a serious security implication? The answer to this is: if the broken templates/defaults are on /usr/share, it would be easy to deploy the fix. So, the compromise solution is: - We can move some configuration data (especially defaults/templates) to /usr/share (machine-types and CPU models could go there). This way we can easily deploy fixes to the defaults, if necessary. - To reuse Qemu models, or machine-types, and not define everything from scratch, libvirt will have to use something like: "-nodefconfig -readconfig /usr/share/qemu/cpu-models-x86.conf" cpu-models-x86.conf is not a configuration file. It is hardware description file. QEMU should not lose capability just because you run it with -nodefconfig. -nodefconfig means that QEMU does not create machine for you, but all parts needed to create a machine that would have been created without -nodefconfig are still present. Not been able to create Nehalem CPU after specifying -nodefconfig is the same as not been able to create virtio-net i.e the bug. (the item below is not something discussed on the call, just something I want to add) To make this work better, we can allow users (humans or machines) to "extend" CPU models on the config file, instead of having to define everything from scratch. So, on /etc (or on a libvirt-generated config) we could have something like: = [cpu] base_cpudef = Nehalem add_features = "vmx" = Then, as long as /usr/share/cpu-models-x86.conf is loaded, the user will be able to reuse the Nehalem CPU model provided by Qemu. And if it will not be loaded? But now when libvirt uses -nodefconfig, those models go away. -nodefconfig means start QEMU in the most minimal state possible. You get what you pay for if you use it. We'll have the same problem with machine configuration files. At some point in time, -nodefconfig will make machine models disappear. It shouldn't. Machine-types are defaults to be used as base, they are not user-provided configuration. And the fact that we decided to store some data outside of the Qemu binary is orthogonal the design decisions in the Qemu command-line and configuration interface. So, this problem is solved if the defaults are easily found on /usr/share. What problem is solved and why are we mixing machine configuration files and cpu configuration files? They are different and should be treated differently. -nodefconfig exists only because there is not machine configuration files currently. With machine configuration files libvirt does not need -nodefconfig because it can create its own machine file and make QEMU use it. So specifying machine file on QEMU's command line implies -nodefconfig. The option itself loses its meaning and can be dropped. No, -nodefconfig means "no default config". As with many projects, we c
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Thu, Mar 22, 2012 at 04:30:55PM +0200, Gleb Natapov wrote: > On Thu, Mar 22, 2012 at 10:31:21AM -0300, Eduardo Habkost wrote: > > On Thu, Mar 22, 2012 at 11:32:44AM +0200, Gleb Natapov wrote: > > > What does this mean? Will -nodefconfig disable loading of bios.bin, > > > option roms, keymaps? > > > > Correcting myself: loading of _config_ files on /usr/share. ROM images > > are opaque data to be presented to the guest somehow, just like a disk > > image or kernel binary. But maybe keymaps will become "configuration" > > someday, I really don't know. > > > Where do you draw the line between "opaque data" and configuration. CPU > models are also something that is present to a guest somehow. Just the fact that it's in a structured key=value format that Qemu itself will interpret before exposing something to the guest. Yes, it's a bit arbitrary. If we could make everything "configuration data", we would (or that's what I think Anthony is pushing for--I hope he will reply and clarify that). > Are you > consider ROMs to be "opaque data" because they are binary and CPU models > to be config just because it is ascii file? Not just "ascii file", but structured (and relatively small) [section]key=value data. If BIOSes were not opaque binary code and could be converted to a small set of config sections and key=values just like cpudefs, one could argue that BIOSes could become configuration data, too. > What if we pre-process CPU > models into binary for QEMU to read will it magically stop being > configuration? Doing the reverse (transforming simple [section]key=value data to a binary format) would just be silly and wouldn't gain us anything. The point here is that we (Qemu) seem to be moving towards a design where most things are structured "configuration data" that fits on a [section]key=value model, and Qemu just interprets that structured data to build a virtual machine. (That's why I said that perhaps keymaps could become configuration someday. Because maybe they can be converted to a key=value model relatively easily) > > > > > Doing this would make it impossible to deploy fixes to users if we > > > > > evern > > > > > find out that the default configuration file had a serious bug. What > > > > > if > > > > > a bug in our default configuration file has a serious security > > > > > implication? > > > > > > > > The answer to this is: if the broken templates/defaults are on > > > > /usr/share, it would be easy to deploy the fix. > > > > > > > > So, the compromise solution is: > > > > > > > > - We can move some configuration data (especially defaults/templates) > > > > to /usr/share (machine-types and CPU models could go there). This > > > > way we can easily deploy fixes to the defaults, if necessary. > > > > - To reuse Qemu models, or machine-types, and not define everything from > > > > scratch, libvirt will have to use something like: > > > > "-nodefconfig -readconfig /usr/share/qemu/cpu-models-x86.conf" > > > > > > > cpu-models-x86.conf is not a configuration file. It is hardware > > > description file. QEMU should not lose capability just because you run > > > it with -nodefconfig. -nodefconfig means that QEMU does not create > > > machine for you, but all parts needed to create a machine that would have > > > been created without -nodefconfig are still present. Not been able to > > > create Nehalem CPU after specifying -nodefconfig is the same as not been > > > able to create virtio-net i.e the bug. > > > > > > The current design direction Qemu seems to be following is different > > from that: hardware description is also considered "configuration" just > > like actual machine configuration. Anthony, please correct me if I am > > wrong. > That's a bug. Why trying to rationalize it now instead of fixing it. It's just a bug for you because you disagree with the current design. You can call it rationalization, yes; I am just accepting Anthony's proposal because it's equally good (to me) as what you are proposing. > It > was fixed in RHEL by the same person who introduced it in upstream in > the first place. He just forgot to send the fix upstream. Does bug that > is present for a long time is promoted to a feature? John didn't forget it, he knew that upstream could go in a different direction. The RHEL6 patch description has this: "Note this is intended as an interim work-around for rhel6.0. While the new location of the config file should remain the same, the mechanism to direct qemu to it will likely differ going forward." > > > > (the item below is not something discussed on the call, just something I > > > > want to add) > > > > > > > > To make this work better, we can allow users (humans or machines) to > > > > "extend" CPU models on the config file, instead of having to define > > > > everything from scratch. So, on /etc (or on a libvirt-generated config) > > > > we could have something like: > > > > > > > > = > > > > [cpu] > > > > base_cpudef = Nehalem >
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Thu, Mar 22, 2012 at 10:31:21AM -0300, Eduardo Habkost wrote: > On Thu, Mar 22, 2012 at 11:32:44AM +0200, Gleb Natapov wrote: > > On Tue, Mar 13, 2012 at 11:53:19AM -0300, Eduardo Habkost wrote: > > > So, trying to summarize what was discussed in the call: > > > > > > On Mon, Mar 12, 2012 at 10:08:10AM -0300, Eduardo Habkost wrote: > > > > > Let's say we moved CPU definitions to /usr/share/qemu/cpu-models.xml. > > > > > > > > > > Obviously, we'd want a command line option to be able to change that > > > > > location so we'd introduce -cpu-models PATH. > > > > > > > > > > But we want all of our command line options to be settable by the > > > > > global configuration file so we would have a cpu-model=PATH to the > > > > > configuration file. > > > > > > > > > > But why hard code a path when we can just set the default path in the > > > > > configuration file so let's avoid hard coding and just put > > > > > cpu-models=/usr/share/qemu/cpu-models.xml in the default > > > > > configuration file. > > > > > > > > We wouldn't do the above. > > > > > > > > -nodefconfig should disable the loading of files on /etc, but it > > > > shouldn't disable loading internal non-configurable data that we just > > > > happened to choose to store outside the qemu binary because it makes > > > > development easier. > > > > > > The statement above is the one not fulfilled by the compromise solution: > > > -nodefconfig would really disable the loading of files on /usr/share. > > > > > What does this mean? Will -nodefconfig disable loading of bios.bin, > > option roms, keymaps? > > Correcting myself: loading of _config_ files on /usr/share. ROM images > are opaque data to be presented to the guest somehow, just like a disk > image or kernel binary. But maybe keymaps will become "configuration" > someday, I really don't know. > Where do you draw the line between "opaque data" and configuration. CPU models are also something that is present to a guest somehow. Are you consider ROMs to be "opaque data" because they are binary and CPU models to be config just because it is ascii file? What if we pre-process CPU models into binary for QEMU to read will it magically stop being configuration? > > > > > > > > > Doing this would make it impossible to deploy fixes to users if we evern > > > > find out that the default configuration file had a serious bug. What if > > > > a bug in our default configuration file has a serious security > > > > implication? > > > > > > The answer to this is: if the broken templates/defaults are on > > > /usr/share, it would be easy to deploy the fix. > > > > > > So, the compromise solution is: > > > > > > - We can move some configuration data (especially defaults/templates) > > > to /usr/share (machine-types and CPU models could go there). This > > > way we can easily deploy fixes to the defaults, if necessary. > > > - To reuse Qemu models, or machine-types, and not define everything from > > > scratch, libvirt will have to use something like: > > > "-nodefconfig -readconfig /usr/share/qemu/cpu-models-x86.conf" > > > > > cpu-models-x86.conf is not a configuration file. It is hardware > > description file. QEMU should not lose capability just because you run > > it with -nodefconfig. -nodefconfig means that QEMU does not create > > machine for you, but all parts needed to create a machine that would have > > been created without -nodefconfig are still present. Not been able to > > create Nehalem CPU after specifying -nodefconfig is the same as not been > > able to create virtio-net i.e the bug. > > > The current design direction Qemu seems to be following is different > from that: hardware description is also considered "configuration" just > like actual machine configuration. Anthony, please correct me if I am > wrong. That's a bug. Why trying to rationalize it now instead of fixing it. It was fixed in RHEL by the same person who introduced it in upstream in the first place. He just forgot to send the fix upstream. Does bug that is present for a long time is promoted to a feature? > > > What you propose is to have two levels of "configuration" (or > descriptions, or whatever we call it): > > 1) Hardware descriptions (or templates, or models, whatever we call it), >that are not editable by the user (and not disabled by -nodefconfig). >This may include CPU models, hardware emulation implemented in >another language, machine-types, and other stuff that is part of >"what Qemu always provides". > 2) Actual machine configuration file, that is configurable and editable >by the user, and normally loaded from /etc on from the command-line. > > The only problem is: the Qemu design simply doesn't have this > distinction today (well, it _has_, the only difference is that today > item (1) is almost completely coded inside tables in .c files). So if we > want to go in that direction we have to agree this will be part of the > Qemu design. > > I am not strongly inclined ei
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Thu, Mar 22, 2012 at 11:32:44AM +0200, Gleb Natapov wrote: > On Tue, Mar 13, 2012 at 11:53:19AM -0300, Eduardo Habkost wrote: > > So, trying to summarize what was discussed in the call: > > > > On Mon, Mar 12, 2012 at 10:08:10AM -0300, Eduardo Habkost wrote: > > > > Let's say we moved CPU definitions to /usr/share/qemu/cpu-models.xml. > > > > > > > > Obviously, we'd want a command line option to be able to change that > > > > location so we'd introduce -cpu-models PATH. > > > > > > > > But we want all of our command line options to be settable by the > > > > global configuration file so we would have a cpu-model=PATH to the > > > > configuration file. > > > > > > > > But why hard code a path when we can just set the default path in the > > > > configuration file so let's avoid hard coding and just put > > > > cpu-models=/usr/share/qemu/cpu-models.xml in the default > > > > configuration file. > > > > > > We wouldn't do the above. > > > > > > -nodefconfig should disable the loading of files on /etc, but it > > > shouldn't disable loading internal non-configurable data that we just > > > happened to choose to store outside the qemu binary because it makes > > > development easier. > > > > The statement above is the one not fulfilled by the compromise solution: > > -nodefconfig would really disable the loading of files on /usr/share. > > > What does this mean? Will -nodefconfig disable loading of bios.bin, > option roms, keymaps? Correcting myself: loading of _config_ files on /usr/share. ROM images are opaque data to be presented to the guest somehow, just like a disk image or kernel binary. But maybe keymaps will become "configuration" someday, I really don't know. > > > > > > Doing this would make it impossible to deploy fixes to users if we evern > > > find out that the default configuration file had a serious bug. What if > > > a bug in our default configuration file has a serious security > > > implication? > > > > The answer to this is: if the broken templates/defaults are on > > /usr/share, it would be easy to deploy the fix. > > > > So, the compromise solution is: > > > > - We can move some configuration data (especially defaults/templates) > > to /usr/share (machine-types and CPU models could go there). This > > way we can easily deploy fixes to the defaults, if necessary. > > - To reuse Qemu models, or machine-types, and not define everything from > > scratch, libvirt will have to use something like: > > "-nodefconfig -readconfig /usr/share/qemu/cpu-models-x86.conf" > > > cpu-models-x86.conf is not a configuration file. It is hardware > description file. QEMU should not lose capability just because you run > it with -nodefconfig. -nodefconfig means that QEMU does not create > machine for you, but all parts needed to create a machine that would have > been created without -nodefconfig are still present. Not been able to > create Nehalem CPU after specifying -nodefconfig is the same as not been > able to create virtio-net i.e the bug. The current design direction Qemu seems to be following is different from that: hardware description is also considered "configuration" just like actual machine configuration. Anthony, please correct me if I am wrong. What you propose is to have two levels of "configuration" (or descriptions, or whatever we call it): 1) Hardware descriptions (or templates, or models, whatever we call it), that are not editable by the user (and not disabled by -nodefconfig). This may include CPU models, hardware emulation implemented in another language, machine-types, and other stuff that is part of "what Qemu always provides". 2) Actual machine configuration file, that is configurable and editable by the user, and normally loaded from /etc on from the command-line. The only problem is: the Qemu design simply doesn't have this distinction today (well, it _has_, the only difference is that today item (1) is almost completely coded inside tables in .c files). So if we want to go in that direction we have to agree this will be part of the Qemu design. I am not strongly inclined either way. Both approaches look good to me, we just have to decide where we are going, because we're are in this weird position todady because we never decided it explicitly, libvirt expected one thing, and we implemented something else. On the one hand I think the "two-layer" design gives us more freedom to move stuff outside .c files and change implementation details, and fits how we have been doing until today with machine types and built-in CPU models, keymaps, etc. On the other hand, I think not having this distinction between "machine configuration" and "hardware description" may be a good thing. For example: today there are two different ways of enabling a feature on a CPU: defining a new model, and adding a flag to "-cpu". And I think this asymmetry shouldn't be there: you just need a good system to define a CPU, a good set of defaults/templates, and a goo
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Tue, Mar 13, 2012 at 11:53:19AM -0300, Eduardo Habkost wrote: > So, trying to summarize what was discussed in the call: > > On Mon, Mar 12, 2012 at 10:08:10AM -0300, Eduardo Habkost wrote: > > > Let's say we moved CPU definitions to /usr/share/qemu/cpu-models.xml. > > > > > > Obviously, we'd want a command line option to be able to change that > > > location so we'd introduce -cpu-models PATH. > > > > > > But we want all of our command line options to be settable by the > > > global configuration file so we would have a cpu-model=PATH to the > > > configuration file. > > > > > > But why hard code a path when we can just set the default path in the > > > configuration file so let's avoid hard coding and just put > > > cpu-models=/usr/share/qemu/cpu-models.xml in the default > > > configuration file. > > > > We wouldn't do the above. > > > > -nodefconfig should disable the loading of files on /etc, but it > > shouldn't disable loading internal non-configurable data that we just > > happened to choose to store outside the qemu binary because it makes > > development easier. > > The statement above is the one not fulfilled by the compromise solution: > -nodefconfig would really disable the loading of files on /usr/share. > What does this mean? Will -nodefconfig disable loading of bios.bin, option roms, keymaps? > > > > Really, the requirement of a "default configuration file" is a problem > > by itself. Qemu should not require a default configuration file to work, > > and it shouldn't require users to copy the default configuration file to > > change options from the default. > > The statement above is only partly true. The default configuration file > would be still needed, but if defaults are stored on /usr/share, I will > be happy with it. > > My main problem was with the need to _copy_ or edit a non-trivial > default config file. If the not-often-edited defaults/templates are > easily found on /usr/share to be used with -readconfig, I will be happy > with this solution, even if -nodefconfig disable the files on > /usr/share. > > > > > Doing this would make it impossible to deploy fixes to users if we evern > > find out that the default configuration file had a serious bug. What if > > a bug in our default configuration file has a serious security > > implication? > > The answer to this is: if the broken templates/defaults are on > /usr/share, it would be easy to deploy the fix. > > So, the compromise solution is: > > - We can move some configuration data (especially defaults/templates) > to /usr/share (machine-types and CPU models could go there). This > way we can easily deploy fixes to the defaults, if necessary. > - To reuse Qemu models, or machine-types, and not define everything from > scratch, libvirt will have to use something like: > "-nodefconfig -readconfig /usr/share/qemu/cpu-models-x86.conf" > cpu-models-x86.conf is not a configuration file. It is hardware description file. QEMU should not lose capability just because you run it with -nodefconfig. -nodefconfig means that QEMU does not create machine for you, but all parts needed to create a machine that would have been created without -nodefconfig are still present. Not been able to create Nehalem CPU after specifying -nodefconfig is the same as not been able to create virtio-net i.e the bug. > > (the item below is not something discussed on the call, just something I > want to add) > > To make this work better, we can allow users (humans or machines) to > "extend" CPU models on the config file, instead of having to define > everything from scratch. So, on /etc (or on a libvirt-generated config) > we could have something like: > > = > [cpu] > base_cpudef = Nehalem > add_features = "vmx" > = > > Then, as long as /usr/share/cpu-models-x86.conf is loaded, the user will > be able to reuse the Nehalem CPU model provided by Qemu. > And if it will not be loaded? > > > > > > > > But now when libvirt uses -nodefconfig, those models go away. > > > -nodefconfig means start QEMU in the most minimal state possible. > > > You get what you pay for if you use it. > > > > > > We'll have the same problem with machine configuration files. At > > > some point in time, -nodefconfig will make machine models disappear. > > > > It shouldn't. Machine-types are defaults to be used as base, they are > > not user-provided configuration. And the fact that we decided to store > > some data outside of the Qemu binary is orthogonal the design decisions > > in the Qemu command-line and configuration interface. > > So, this problem is solved if the defaults are easily found on > /usr/share. > What problem is solved and why are we mixing machine configuration files and cpu configuration files? They are different and should be treated differently. -nodefconfig exists only because there is not machine configuration files currently. With machine configuration files libvirt does not need -nodefconfig because it can c
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
- Original Message - > On 03/12/2012 10:19 PM, Ayal Baron wrote: > > > > > > - Original Message - > >> On 03/12/2012 02:12 PM, Itamar Heim wrote: > >>> On 03/12/2012 09:01 PM, Anthony Liguori wrote: > > It's a trade off. From a RAS perspective, it's helpful to have > information about the host available in the guest. > > If you're already exposing a compatible family, exposing the > actual > processor seems to be worth the extra effort. > >>> > >>> only if the entire cluster is (and will be?) identical cpu. > >> > >> At least in my experience, this isn't unusual. > > > > I can definitely see places choosing homogeneous hardware and > > upgrading every few years. > > Giving them max capabilities for their cluster sounds logical to > > me. > > Esp. cloud providers. > > they would get same performance as from the matching "cpu family". > only difference would be if the guest known the name of the host cpu. > > > > >> > >>> or if you don't care about live migration i guess, which could be > >>> hte case for > >>> clouds, then again, not sure a cloud provider would want to > >>> expose > >>> the physical > >>> cpu to the tenant. > >> > >> Depends on the type of cloud you're building, I guess. > >> > > > > Wouldn't this affect a simple startup of a VM with a different CPU > > (if motherboard changed as well cause reactivation issues in > > windows and fun things like that)? > > that's an interesting question, I have to assume this works though, > since we didn't see issues with changing the cpu family for guests so > far. > assumption... :) I'd try changing twice in a row (run VM, stop, change family, restart VM, stop, change family restart VM). -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
So, trying to summarize what was discussed in the call: On Mon, Mar 12, 2012 at 10:08:10AM -0300, Eduardo Habkost wrote: > > Let's say we moved CPU definitions to /usr/share/qemu/cpu-models.xml. > > > > Obviously, we'd want a command line option to be able to change that > > location so we'd introduce -cpu-models PATH. > > > > But we want all of our command line options to be settable by the > > global configuration file so we would have a cpu-model=PATH to the > > configuration file. > > > > But why hard code a path when we can just set the default path in the > > configuration file so let's avoid hard coding and just put > > cpu-models=/usr/share/qemu/cpu-models.xml in the default > > configuration file. > > We wouldn't do the above. > > -nodefconfig should disable the loading of files on /etc, but it > shouldn't disable loading internal non-configurable data that we just > happened to choose to store outside the qemu binary because it makes > development easier. The statement above is the one not fulfilled by the compromise solution: -nodefconfig would really disable the loading of files on /usr/share. > > Really, the requirement of a "default configuration file" is a problem > by itself. Qemu should not require a default configuration file to work, > and it shouldn't require users to copy the default configuration file to > change options from the default. The statement above is only partly true. The default configuration file would be still needed, but if defaults are stored on /usr/share, I will be happy with it. My main problem was with the need to _copy_ or edit a non-trivial default config file. If the not-often-edited defaults/templates are easily found on /usr/share to be used with -readconfig, I will be happy with this solution, even if -nodefconfig disable the files on /usr/share. > > Doing this would make it impossible to deploy fixes to users if we evern > find out that the default configuration file had a serious bug. What if > a bug in our default configuration file has a serious security > implication? The answer to this is: if the broken templates/defaults are on /usr/share, it would be easy to deploy the fix. So, the compromise solution is: - We can move some configuration data (especially defaults/templates) to /usr/share (machine-types and CPU models could go there). This way we can easily deploy fixes to the defaults, if necessary. - To reuse Qemu models, or machine-types, and not define everything from scratch, libvirt will have to use something like: "-nodefconfig -readconfig /usr/share/qemu/cpu-models-x86.conf" (the item below is not something discussed on the call, just something I want to add) To make this work better, we can allow users (humans or machines) to "extend" CPU models on the config file, instead of having to define everything from scratch. So, on /etc (or on a libvirt-generated config) we could have something like: = [cpu] base_cpudef = Nehalem add_features = "vmx" = Then, as long as /usr/share/cpu-models-x86.conf is loaded, the user will be able to reuse the Nehalem CPU model provided by Qemu. > > > > > But now when libvirt uses -nodefconfig, those models go away. > > -nodefconfig means start QEMU in the most minimal state possible. > > You get what you pay for if you use it. > > > > We'll have the same problem with machine configuration files. At > > some point in time, -nodefconfig will make machine models disappear. > > It shouldn't. Machine-types are defaults to be used as base, they are > not user-provided configuration. And the fact that we decided to store > some data outside of the Qemu binary is orthogonal the design decisions > in the Qemu command-line and configuration interface. So, this problem is solved if the defaults are easily found on /usr/share. We still have the backwards compatibility problem for pc-1.0, pc-1.1, and so on. But that can be discussed later, when we actually move machine-types to somewhere outside .c files. > > As I said previously, requiring generation of opaque config files (and > "copy the default config file and change it" is included on my > definition of "generation of opaque config files") is poor design, IMO. > I bet this even has an entry in some design anti-pattern catalog > somewhere. This problem is also solved if the defaults are deployed on /usr/share and just reused/included by the config files on /etc. -- Eduardo -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/12/2012 10:19 PM, Ayal Baron wrote: - Original Message - On 03/12/2012 02:12 PM, Itamar Heim wrote: On 03/12/2012 09:01 PM, Anthony Liguori wrote: It's a trade off. From a RAS perspective, it's helpful to have information about the host available in the guest. If you're already exposing a compatible family, exposing the actual processor seems to be worth the extra effort. only if the entire cluster is (and will be?) identical cpu. At least in my experience, this isn't unusual. I can definitely see places choosing homogeneous hardware and upgrading every few years. Giving them max capabilities for their cluster sounds logical to me. Esp. cloud providers. they would get same performance as from the matching "cpu family". only difference would be if the guest known the name of the host cpu. or if you don't care about live migration i guess, which could be hte case for clouds, then again, not sure a cloud provider would want to expose the physical cpu to the tenant. Depends on the type of cloud you're building, I guess. Wouldn't this affect a simple startup of a VM with a different CPU (if motherboard changed as well cause reactivation issues in windows and fun things like that)? that's an interesting question, I have to assume this works though, since we didn't see issues with changing the cpu family for guests so far. -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
- Original Message - > On 03/12/2012 02:12 PM, Itamar Heim wrote: > > On 03/12/2012 09:01 PM, Anthony Liguori wrote: > >> > >> It's a trade off. From a RAS perspective, it's helpful to have > >> information about the host available in the guest. > >> > >> If you're already exposing a compatible family, exposing the > >> actual > >> processor seems to be worth the extra effort. > > > > only if the entire cluster is (and will be?) identical cpu. > > At least in my experience, this isn't unusual. I can definitely see places choosing homogeneous hardware and upgrading every few years. Giving them max capabilities for their cluster sounds logical to me. Esp. cloud providers. > > > or if you don't care about live migration i guess, which could be > > hte case for > > clouds, then again, not sure a cloud provider would want to expose > > the physical > > cpu to the tenant. > > Depends on the type of cloud you're building, I guess. > Wouldn't this affect a simple startup of a VM with a different CPU (if motherboard changed as well cause reactivation issues in windows and fun things like that)? Even if the cloud doesn't support live migration, they don't pin VMs to a host. User could shut it down and start it up again and it might run on a different node. Your ephemeral storage would be lost, but persistent image storage could still contain os info pertinent to cpu type. Btw, I don't see why internally they would not support live migration even for when they need to put a host in maintenance etc. live storage migration could take care of the ephemeral storage if that's the issue (albeit take a million years to finish). > >>> ovirt allows to set "cpu family" per cluster. assume tomorrow it > >>> could > >>> do it an > >>> even more granular way. > >>> it could also do it automatically based on subset of flags on all > >>> hosts - but > >>> would it really make sense to expose a set of capabilities which > >>> doesn't exist > >>> in the real world (which iiuc, is pretty much aligned with the > >>> cpu > >>> families?), > >>> that users understand? > >> > >> No, I think the lesson we've learned in QEMU (the hard way) is > >> that > >> exposing a CPU that never existed will cause something to break. > >> Often > >> times, that something is glibc or GCC which tends to be rather > >> epic in > >> terms of failure. > > > > good to hear - I think this is the important part. > > so from that perspective, cpu families sounds the right abstraction > > for general > > use case to me. > > for ovirt, could improve on smaller/dynamic subsets of migration > > domains rather > > than current clusters > > and sounds like you would want to see "expose host cpu for non > > migratable > > guests, or for identical clusters". > > Would it be possible to have a "best available" option in > oVirt-engine that > would assume that all processors are of the same class and fail an > attempt to > add something that's an older class? > > I think that most people probably would start with "best available" > and then > after adding a node fails, revisit the decision and start lowering > the minimum > CPU family (I'm assuming that it's possible to modify the CPU family > over time). But then they'd already have VMs that were started with the better CPU and now it'd change under their feet? or would we start them up with the best and fail to start these VMs on the newly added hosts which have the lower cpu family/type? > > From a QEMU perspective, I think that means having per-family CPU > options and > then Alex's '-cpu best'. But presumably it's also necessary to be > able to > figure out in virsh capabilities what '-cpu best' would be. > > Regards, > > Anthony Liguori > > > ___ > > Arch mailing list > > a...@ovirt.org > > http://lists.ovirt.org/mailman/listinfo/arch > > > > -- > libvir-list mailing list > libvir-list@redhat.com > https://www.redhat.com/mailman/listinfo/libvir-list > -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/12/2012 09:50 PM, Anthony Liguori wrote: On 03/12/2012 02:12 PM, Itamar Heim wrote: On 03/12/2012 09:01 PM, Anthony Liguori wrote: It's a trade off. From a RAS perspective, it's helpful to have information about the host available in the guest. If you're already exposing a compatible family, exposing the actual processor seems to be worth the extra effort. only if the entire cluster is (and will be?) identical cpu. At least in my experience, this isn't unusual. or if you don't care about live migration i guess, which could be hte case for clouds, then again, not sure a cloud provider would want to expose the physical cpu to the tenant. Depends on the type of cloud you're building, I guess. ovirt allows to set "cpu family" per cluster. assume tomorrow it could do it an even more granular way. it could also do it automatically based on subset of flags on all hosts - but would it really make sense to expose a set of capabilities which doesn't exist in the real world (which iiuc, is pretty much aligned with the cpu families?), that users understand? No, I think the lesson we've learned in QEMU (the hard way) is that exposing a CPU that never existed will cause something to break. Often times, that something is glibc or GCC which tends to be rather epic in terms of failure. good to hear - I think this is the important part. so from that perspective, cpu families sounds the right abstraction for general use case to me. for ovirt, could improve on smaller/dynamic subsets of migration domains rather than current clusters and sounds like you would want to see "expose host cpu for non migratable guests, or for identical clusters". Would it be possible to have a "best available" option in oVirt-engine that would assume that all processors are of the same class and fail an attempt to add something that's an older class? I think that most people probably would start with "best available" and then after adding a node fails, revisit the decision and start lowering the minimum CPU family (I'm assuming that it's possible to modify the CPU family over time). iirc, the original implementation for cpu family was start with an empty family, and use the best match from the first host added to the cluster. not sure if that's still the behavior though. worth mentioning the cpu families in ovirt have a 'sort' field to allow starting from best available. and you can change the cpu family of a cluster today as well (with some validations hosts in the cluster match up) From a QEMU perspective, I think that means having per-family CPU options and then Alex's '-cpu best'. But presumably it's also necessary to be able to figure out in virsh capabilities what '-cpu best' would be. if sticking to cpu families, updating the config with name/prioirty of the families twice a year (or by user) seems good enough to me... Regards, Anthony Liguori ___ Arch mailing list a...@ovirt.org http://lists.ovirt.org/mailman/listinfo/arch -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/12/2012 02:12 PM, Itamar Heim wrote: On 03/12/2012 09:01 PM, Anthony Liguori wrote: It's a trade off. From a RAS perspective, it's helpful to have information about the host available in the guest. If you're already exposing a compatible family, exposing the actual processor seems to be worth the extra effort. only if the entire cluster is (and will be?) identical cpu. At least in my experience, this isn't unusual. or if you don't care about live migration i guess, which could be hte case for clouds, then again, not sure a cloud provider would want to expose the physical cpu to the tenant. Depends on the type of cloud you're building, I guess. ovirt allows to set "cpu family" per cluster. assume tomorrow it could do it an even more granular way. it could also do it automatically based on subset of flags on all hosts - but would it really make sense to expose a set of capabilities which doesn't exist in the real world (which iiuc, is pretty much aligned with the cpu families?), that users understand? No, I think the lesson we've learned in QEMU (the hard way) is that exposing a CPU that never existed will cause something to break. Often times, that something is glibc or GCC which tends to be rather epic in terms of failure. good to hear - I think this is the important part. so from that perspective, cpu families sounds the right abstraction for general use case to me. for ovirt, could improve on smaller/dynamic subsets of migration domains rather than current clusters and sounds like you would want to see "expose host cpu for non migratable guests, or for identical clusters". Would it be possible to have a "best available" option in oVirt-engine that would assume that all processors are of the same class and fail an attempt to add something that's an older class? I think that most people probably would start with "best available" and then after adding a node fails, revisit the decision and start lowering the minimum CPU family (I'm assuming that it's possible to modify the CPU family over time). From a QEMU perspective, I think that means having per-family CPU options and then Alex's '-cpu best'. But presumably it's also necessary to be able to figure out in virsh capabilities what '-cpu best' would be. Regards, Anthony Liguori ___ Arch mailing list a...@ovirt.org http://lists.ovirt.org/mailman/listinfo/arch -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/12/2012 09:01 PM, Anthony Liguori wrote: On 03/12/2012 01:53 PM, Itamar Heim wrote: On 03/11/2012 05:33 PM, Anthony Liguori wrote: On 03/11/2012 09:56 AM, Gleb Natapov wrote: On Sun, Mar 11, 2012 at 09:12:58AM -0500, Anthony Liguori wrote: -cpu best wouldn't solve this. You need a read/write configuration file where QEMU probes the available CPU and records it to be used for the lifetime of the VM. That what I thought too, but this shouldn't be the case (Avi's idea). We need two things: 1) CPU model config should be per machine type. 2) QEMU should refuse to start if it cannot create cpu exactly as specified by model config. This would either mean: A. pc-1.1 uses -cpu best with a fixed mask for 1.1 B. pc-1.1 hardcodes Westmere or some other family (A) would imply a different CPU if you moved the machine from one system to another. I would think this would be very problematic from a user's perspective. (B) would imply that we had to choose the least common denominator which is essentially what we do today with qemu64. If you want to just switch qemu64 to Conroe, I don't think that's a huge difference from what we have today. It's a discussion about how we handle this up and down the stack. The question is who should define and manage CPU compatibility. Right now QEMU does to a certain degree, libvirt discards this and does it's own thing, and VDSM/ovirt-engine assume that we're providing something and has built a UI around it. If we want QEMU to be usable without management layer then QEMU should provide stable CPU models. Stable in a sense that qemu, kernel or CPU upgrade does not change what guest sees. We do this today by exposing -cpu qemu64 by default. If all you're advocating is doing -cpu Conroe by default, that's fine. But I fail to see where this fits into the larger discussion here. The problem to solve is: I want to use the largest possible subset of CPU features available uniformly throughout my datacenter. QEMU and libvirt have single node views so they cannot solve this problem on their own. Whether that subset is a generic Westmere-like processor that never existed IRL or a specific Westmere processor seems like a decision that should be made by the datacenter level manager with the node level view. If I have a homogeneous environments of Xeon 7540, I would probably like to see a Xeon 7540 in my guest. Doesn't it make sense to enable the management tool to make this decision? literally, or in capabilities? literally means you want to allow passing the cpu name to be exposed to the guest? Yes, literally. Xen exposes the host CPUID to the guest for PV. Both PHYP (IBM System P) and z/VM (IBM System Z) do the same. What does VMware expose to guests by default? if in capabilities, how would it differ from choosing the correct "cpu family"? it wouldn't really be identical (say, number of cores/sockets and no VT for time being) It's a trade off. From a RAS perspective, it's helpful to have information about the host available in the guest. If you're already exposing a compatible family, exposing the actual processor seems to be worth the extra effort. only if the entire cluster is (and will be?) identical cpu. or if you don't care about live migration i guess, which could be hte case for clouds, then again, not sure a cloud provider would want to expose the physical cpu to the tenant. ovirt allows to set "cpu family" per cluster. assume tomorrow it could do it an even more granular way. it could also do it automatically based on subset of flags on all hosts - but would it really make sense to expose a set of capabilities which doesn't exist in the real world (which iiuc, is pretty much aligned with the cpu families?), that users understand? No, I think the lesson we've learned in QEMU (the hard way) is that exposing a CPU that never existed will cause something to break. Often times, that something is glibc or GCC which tends to be rather epic in terms of failure. good to hear - I think this is the important part. so from that perspective, cpu families sounds the right abstraction for general use case to me. for ovirt, could improve on smaller/dynamic subsets of migration domains rather than current clusters and sounds like you would want to see "expose host cpu for non migratable guests, or for identical clusters". -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/12/2012 01:53 PM, Itamar Heim wrote: On 03/11/2012 05:33 PM, Anthony Liguori wrote: On 03/11/2012 09:56 AM, Gleb Natapov wrote: On Sun, Mar 11, 2012 at 09:12:58AM -0500, Anthony Liguori wrote: -cpu best wouldn't solve this. You need a read/write configuration file where QEMU probes the available CPU and records it to be used for the lifetime of the VM. That what I thought too, but this shouldn't be the case (Avi's idea). We need two things: 1) CPU model config should be per machine type. 2) QEMU should refuse to start if it cannot create cpu exactly as specified by model config. This would either mean: A. pc-1.1 uses -cpu best with a fixed mask for 1.1 B. pc-1.1 hardcodes Westmere or some other family (A) would imply a different CPU if you moved the machine from one system to another. I would think this would be very problematic from a user's perspective. (B) would imply that we had to choose the least common denominator which is essentially what we do today with qemu64. If you want to just switch qemu64 to Conroe, I don't think that's a huge difference from what we have today. It's a discussion about how we handle this up and down the stack. The question is who should define and manage CPU compatibility. Right now QEMU does to a certain degree, libvirt discards this and does it's own thing, and VDSM/ovirt-engine assume that we're providing something and has built a UI around it. If we want QEMU to be usable without management layer then QEMU should provide stable CPU models. Stable in a sense that qemu, kernel or CPU upgrade does not change what guest sees. We do this today by exposing -cpu qemu64 by default. If all you're advocating is doing -cpu Conroe by default, that's fine. But I fail to see where this fits into the larger discussion here. The problem to solve is: I want to use the largest possible subset of CPU features available uniformly throughout my datacenter. QEMU and libvirt have single node views so they cannot solve this problem on their own. Whether that subset is a generic Westmere-like processor that never existed IRL or a specific Westmere processor seems like a decision that should be made by the datacenter level manager with the node level view. If I have a homogeneous environments of Xeon 7540, I would probably like to see a Xeon 7540 in my guest. Doesn't it make sense to enable the management tool to make this decision? literally, or in capabilities? literally means you want to allow passing the cpu name to be exposed to the guest? Yes, literally. Xen exposes the host CPUID to the guest for PV. Both PHYP (IBM System P) and z/VM (IBM System Z) do the same. What does VMware expose to guests by default? if in capabilities, how would it differ from choosing the correct "cpu family"? it wouldn't really be identical (say, number of cores/sockets and no VT for time being) It's a trade off. From a RAS perspective, it's helpful to have information about the host available in the guest. If you're already exposing a compatible family, exposing the actual processor seems to be worth the extra effort. ovirt allows to set "cpu family" per cluster. assume tomorrow it could do it an even more granular way. it could also do it automatically based on subset of flags on all hosts - but would it really make sense to expose a set of capabilities which doesn't exist in the real world (which iiuc, is pretty much aligned with the cpu families?), that users understand? No, I think the lesson we've learned in QEMU (the hard way) is that exposing a CPU that never existed will cause something to break. Often times, that something is glibc or GCC which tends to be rather epic in terms of failure. Regards, Anthony Liguori -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/11/2012 05:33 PM, Anthony Liguori wrote: On 03/11/2012 09:56 AM, Gleb Natapov wrote: On Sun, Mar 11, 2012 at 09:12:58AM -0500, Anthony Liguori wrote: -cpu best wouldn't solve this. You need a read/write configuration file where QEMU probes the available CPU and records it to be used for the lifetime of the VM. That what I thought too, but this shouldn't be the case (Avi's idea). We need two things: 1) CPU model config should be per machine type. 2) QEMU should refuse to start if it cannot create cpu exactly as specified by model config. This would either mean: A. pc-1.1 uses -cpu best with a fixed mask for 1.1 B. pc-1.1 hardcodes Westmere or some other family (A) would imply a different CPU if you moved the machine from one system to another. I would think this would be very problematic from a user's perspective. (B) would imply that we had to choose the least common denominator which is essentially what we do today with qemu64. If you want to just switch qemu64 to Conroe, I don't think that's a huge difference from what we have today. It's a discussion about how we handle this up and down the stack. The question is who should define and manage CPU compatibility. Right now QEMU does to a certain degree, libvirt discards this and does it's own thing, and VDSM/ovirt-engine assume that we're providing something and has built a UI around it. If we want QEMU to be usable without management layer then QEMU should provide stable CPU models. Stable in a sense that qemu, kernel or CPU upgrade does not change what guest sees. We do this today by exposing -cpu qemu64 by default. If all you're advocating is doing -cpu Conroe by default, that's fine. But I fail to see where this fits into the larger discussion here. The problem to solve is: I want to use the largest possible subset of CPU features available uniformly throughout my datacenter. QEMU and libvirt have single node views so they cannot solve this problem on their own. Whether that subset is a generic Westmere-like processor that never existed IRL or a specific Westmere processor seems like a decision that should be made by the datacenter level manager with the node level view. If I have a homogeneous environments of Xeon 7540, I would probably like to see a Xeon 7540 in my guest. Doesn't it make sense to enable the management tool to make this decision? literally, or in capabilities? literally means you want to allow passing the cpu name to be exposed to the guest? if in capabilities, how would it differ from choosing the correct "cpu family"? it wouldn't really be identical (say, number of cores/sockets and no VT for time being) ovirt allows to set "cpu family" per cluster. assume tomorrow it could do it an even more granular way. it could also do it automatically based on subset of flags on all hosts - but would it really make sense to expose a set of capabilities which doesn't exist in the real world (which iiuc, is pretty much aligned with the cpu families?), that users understand? -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/12/2012 01:30 PM, Eduardo Habkost wrote: On Mon, Mar 12, 2012 at 06:41:06PM +0100, Andreas Färber wrote: Am 12.03.2012 17:50, schrieb Eduardo Habkost: On Mon, Mar 12, 2012 at 04:49:47PM +0100, Andreas Färber wrote: [...] IMO interpreting an explicit -cpu parameter depending on -M would be wrong. Changing the default CPU based on -M is fine with me. For an explicit argument we would need Westmere-1.0 analog to pc-1.0. Then the user gets what the user asks for, without unexpected magic. It is not unexpected magic. It would be a documented mechanism: "-cpu Nehalem-1.0" and "-cpu Nehalem-1.1" would have the same meaning every time, with any machine-type, but "-cpu Nehalem" would be an alias, whose meaning depends on the machine-type. Otherwise we would be stuck with a broken "Nehalem" model forever, and we don't want that. Not quite what I meant: In light of QOM we should be able to instantiate a CPU based on its name and optional parameters IMO. No dependency on the machine, please. An alias sure, but if the user explicitly says -cpu Nehalem then on 1.1 it should always be an alias to Nehalem-1.1 whether the machine is -M pc-0.15 or pc. If no -cpu was specified by the user, then choosing a default of Nehalem-1.0 for pc-1.0 is fine. Just trying to keep separate things separate here. As Gleb explained, things aren't really separated: "qemu-1.1 -M pc-1.0 -cpu Nehalem" should result in the same machine as "qemu-1.0 -cpu Nehalem", no difference should be visible to the guest. simply make incompatible changes. So this is easy. CPU's need to be qdev/QOM and the various cpuid settings need to be done through qdev properties. Then you can just add globals to the machine definition. No different than what we do with virtio-blk. Regards, Anthony Liguori Also keep in mind linux-user. There's no concept of a machine there, but there's a cpu_copy() function used for forking that tries to re-create the CPU based on its model. So currently cpu_*_init(env->cpu_model_str) needs to be able to recreate an identical CPU through the central code path, without access to a QEMUMachine. So just translate the CPU alias given to "-cpu" to the true CPU model name as soon as possible, at the command-line-handling code, so the rest of the code always see the true CPU model name. After all, the need to make the aliases is a command-line interface compatibility problem, so it makes sense to handle this at the command-line-handling code. -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Mon, Mar 12, 2012 at 06:41:06PM +0100, Andreas Färber wrote: > Am 12.03.2012 17:50, schrieb Eduardo Habkost: > > On Mon, Mar 12, 2012 at 04:49:47PM +0100, Andreas Färber wrote: [...] > >> IMO interpreting an explicit -cpu parameter depending on -M would be > >> wrong. Changing the default CPU based on -M is fine with me. For an > >> explicit argument we would need Westmere-1.0 analog to pc-1.0. Then the > >> user gets what the user asks for, without unexpected magic. > > > > It is not unexpected magic. It would be a documented mechanism: > > "-cpu Nehalem-1.0" and "-cpu Nehalem-1.1" would have the same meaning > > every time, with any machine-type, but "-cpu Nehalem" would be an alias, > > whose meaning depends on the machine-type. > > > > Otherwise we would be stuck with a broken "Nehalem" model forever, and > > we don't want that. > > Not quite what I meant: In light of QOM we should be able to instantiate > a CPU based on its name and optional parameters IMO. No dependency on > the machine, please. An alias sure, but if the user explicitly says -cpu > Nehalem then on 1.1 it should always be an alias to Nehalem-1.1 whether > the machine is -M pc-0.15 or pc. If no -cpu was specified by the user, > then choosing a default of Nehalem-1.0 for pc-1.0 is fine. Just trying > to keep separate things separate here. As Gleb explained, things aren't really separated: "qemu-1.1 -M pc-1.0 -cpu Nehalem" should result in the same machine as "qemu-1.0 -cpu Nehalem", no difference should be visible to the guest. simply make incompatible changes. > > Also keep in mind linux-user. There's no concept of a machine there, but > there's a cpu_copy() function used for forking that tries to re-create > the CPU based on its model. So currently cpu_*_init(env->cpu_model_str) > needs to be able to recreate an identical CPU through the central code > path, without access to a QEMUMachine. So just translate the CPU alias given to "-cpu" to the true CPU model name as soon as possible, at the command-line-handling code, so the rest of the code always see the true CPU model name. After all, the need to make the aliases is a command-line interface compatibility problem, so it makes sense to handle this at the command-line-handling code. -- Eduardo -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 12.03.2012, at 18:53, Andreas Färber wrote: > Am 12.03.2012 18:47, schrieb Peter Maydell: >> On 12 March 2012 17:41, Andreas Färber wrote: >>> Also keep in mind linux-user. There's no concept of a machine there, but >>> there's a cpu_copy() function used for forking that tries to re-create >>> the CPU based on its model. >> >> Incidentally, do you know why the linux-user code calls cpu_reset on >> the newly copied CPU state but only for TARGET_I386/SPARC/PPC ? That >> looks very odd to me... > > Incidentally for i386 I do: cpu_reset() is intentionally not part of > cpu_init() there because afterwards the machine or something sets > whether this CPU is a "bsp" (Board Support Package? ;)) and only then > resets it. > > For ppc and sparc I don't know but I'd be surprised if it's necessary > for ppc... Alex? Phew - no idea. Does git blame know more there? :) Alex -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Mon, Mar 12, 2012 at 06:41:06PM +0100, Andreas Färber wrote: > Am 12.03.2012 17:50, schrieb Eduardo Habkost: > > On Mon, Mar 12, 2012 at 04:49:47PM +0100, Andreas Färber wrote: > >> Am 11.03.2012 17:16, schrieb Gleb Natapov: > >>> On Sun, Mar 11, 2012 at 10:33:15AM -0500, Anthony Liguori wrote: > On 03/11/2012 09:56 AM, Gleb Natapov wrote: > > On Sun, Mar 11, 2012 at 09:12:58AM -0500, Anthony Liguori wrote: > >> -cpu best wouldn't solve this. You need a read/write configuration > >> file where QEMU probes the available CPU and records it to be used > >> for the lifetime of the VM. > > That what I thought too, but this shouldn't be the case (Avi's idea). > > We need two things: 1) CPU model config should be per machine type. > > 2) QEMU should refuse to start if it cannot create cpu exactly as > > specified by model config. > > This would either mean: > > A. pc-1.1 uses -cpu best with a fixed mask for 1.1 > > B. pc-1.1 hardcodes Westmere or some other family > > >>> This would mean neither A nor B. May be it wasn't clear but I didn't talk > >>> about -cpu best above. I am talking about any CPU model with fixed meaning > >>> (not host or best which are host cpu dependant). Lets take Nehalem for > >>> example (just to move from Westmere :)). Currently it has level=2. Eduardo > >>> wants to fix it to be 11, but old guests, installed with -cpu Nehalem, > >>> should see the same CPU exactly. How do you do it? Have different > >>> Nehalem definition for pc-1.0 (which level=2) and pc-1.1 (with level=11). > >>> Lets get back to Westmere. It actually has level=11, but that's only > >>> expose another problem. Kernel 3.3 and qemu-1.1 combo will support > >>> architectural PMU which is exposed in cpuid leaf 10. We do not want > >>> guests installed with -cpu Westmere and qemu-1.0 to see architectural > >>> PMU after upgrade. How do you do it? Have different Westmere definitions > >>> for pc-1.0 (does not report PMU) and pc-1.1 (reports PMU). What happens > >>> if you'll try to run qemu-1.1 -cpu Westmere on Kernel < 3.3 (without > >>> PMU support)? Qemu will fail to start. > [...] > >> IMO interpreting an explicit -cpu parameter depending on -M would be > >> wrong. Changing the default CPU based on -M is fine with me. For an > >> explicit argument we would need Westmere-1.0 analog to pc-1.0. Then the > >> user gets what the user asks for, without unexpected magic. > > > > It is not unexpected magic. It would be a documented mechanism: > > "-cpu Nehalem-1.0" and "-cpu Nehalem-1.1" would have the same meaning > > every time, with any machine-type, but "-cpu Nehalem" would be an alias, > > whose meaning depends on the machine-type. > > > > Otherwise we would be stuck with a broken "Nehalem" model forever, and > > we don't want that. > > Not quite what I meant: In light of QOM we should be able to instantiate > a CPU based on its name and optional parameters IMO. No dependency on > the machine, please. An alias sure, but if the user explicitly says -cpu > Nehalem then on 1.1 it should always be an alias to Nehalem-1.1 whether > the machine is -M pc-0.15 or pc. If no -cpu was specified by the user, > then choosing a default of Nehalem-1.0 for pc-1.0 is fine. Just trying > to keep separate things separate here. > Those things are not separate. If user will get Nehalem-1.1 with -M pc-0.15 on qemu-1.1 it will get broken VM. If user uses -M pc-0.15 it should get exactly same machine it gets by running qemu-0.15. Guest should not be able to tell the difference. This is the reason -M exists, anything else is a bug. -- Gleb. -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 12 March 2012 17:41, Andreas Färber wrote: > Also keep in mind linux-user. There's no concept of a machine there, but > there's a cpu_copy() function used for forking that tries to re-create > the CPU based on its model. Incidentally, do you know why the linux-user code calls cpu_reset on the newly copied CPU state but only for TARGET_I386/SPARC/PPC ? That looks very odd to me... -- PMM -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
Am 12.03.2012 18:47, schrieb Peter Maydell: > On 12 March 2012 17:41, Andreas Färber wrote: >> Also keep in mind linux-user. There's no concept of a machine there, but >> there's a cpu_copy() function used for forking that tries to re-create >> the CPU based on its model. > > Incidentally, do you know why the linux-user code calls cpu_reset on > the newly copied CPU state but only for TARGET_I386/SPARC/PPC ? That > looks very odd to me... Incidentally for i386 I do: cpu_reset() is intentionally not part of cpu_init() there because afterwards the machine or something sets whether this CPU is a "bsp" (Board Support Package? ;)) and only then resets it. For ppc and sparc I don't know but I'd be surprised if it's necessary for ppc... Alex? Andreas -- SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Mon, Mar 12, 2012 at 06:53:27PM +0100, Andreas Färber wrote: > Am 12.03.2012 18:47, schrieb Peter Maydell: > > On 12 March 2012 17:41, Andreas Färber wrote: > >> Also keep in mind linux-user. There's no concept of a machine there, but > >> there's a cpu_copy() function used for forking that tries to re-create > >> the CPU based on its model. > > > > Incidentally, do you know why the linux-user code calls cpu_reset on > > the newly copied CPU state but only for TARGET_I386/SPARC/PPC ? That > > looks very odd to me... > > Incidentally for i386 I do: cpu_reset() is intentionally not part of > cpu_init() there because afterwards the machine or something sets > whether this CPU is a "bsp" (Board Support Package? ;)) and only then Boot Strap Processor I guess :) > resets it. > > For ppc and sparc I don't know but I'd be surprised if it's necessary > for ppc... Alex? > > Andreas > > -- > SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany > GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg -- Gleb. -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
Am 12.03.2012 17:50, schrieb Eduardo Habkost: > On Mon, Mar 12, 2012 at 04:49:47PM +0100, Andreas Färber wrote: >> Am 11.03.2012 17:16, schrieb Gleb Natapov: >>> On Sun, Mar 11, 2012 at 10:33:15AM -0500, Anthony Liguori wrote: On 03/11/2012 09:56 AM, Gleb Natapov wrote: > On Sun, Mar 11, 2012 at 09:12:58AM -0500, Anthony Liguori wrote: >> -cpu best wouldn't solve this. You need a read/write configuration >> file where QEMU probes the available CPU and records it to be used >> for the lifetime of the VM. > That what I thought too, but this shouldn't be the case (Avi's idea). > We need two things: 1) CPU model config should be per machine type. > 2) QEMU should refuse to start if it cannot create cpu exactly as > specified by model config. This would either mean: A. pc-1.1 uses -cpu best with a fixed mask for 1.1 B. pc-1.1 hardcodes Westmere or some other family >>> This would mean neither A nor B. May be it wasn't clear but I didn't talk >>> about -cpu best above. I am talking about any CPU model with fixed meaning >>> (not host or best which are host cpu dependant). Lets take Nehalem for >>> example (just to move from Westmere :)). Currently it has level=2. Eduardo >>> wants to fix it to be 11, but old guests, installed with -cpu Nehalem, >>> should see the same CPU exactly. How do you do it? Have different >>> Nehalem definition for pc-1.0 (which level=2) and pc-1.1 (with level=11). >>> Lets get back to Westmere. It actually has level=11, but that's only >>> expose another problem. Kernel 3.3 and qemu-1.1 combo will support >>> architectural PMU which is exposed in cpuid leaf 10. We do not want >>> guests installed with -cpu Westmere and qemu-1.0 to see architectural >>> PMU after upgrade. How do you do it? Have different Westmere definitions >>> for pc-1.0 (does not report PMU) and pc-1.1 (reports PMU). What happens >>> if you'll try to run qemu-1.1 -cpu Westmere on Kernel < 3.3 (without >>> PMU support)? Qemu will fail to start. [...] >> IMO interpreting an explicit -cpu parameter depending on -M would be >> wrong. Changing the default CPU based on -M is fine with me. For an >> explicit argument we would need Westmere-1.0 analog to pc-1.0. Then the >> user gets what the user asks for, without unexpected magic. > > It is not unexpected magic. It would be a documented mechanism: > "-cpu Nehalem-1.0" and "-cpu Nehalem-1.1" would have the same meaning > every time, with any machine-type, but "-cpu Nehalem" would be an alias, > whose meaning depends on the machine-type. > > Otherwise we would be stuck with a broken "Nehalem" model forever, and > we don't want that. Not quite what I meant: In light of QOM we should be able to instantiate a CPU based on its name and optional parameters IMO. No dependency on the machine, please. An alias sure, but if the user explicitly says -cpu Nehalem then on 1.1 it should always be an alias to Nehalem-1.1 whether the machine is -M pc-0.15 or pc. If no -cpu was specified by the user, then choosing a default of Nehalem-1.0 for pc-1.0 is fine. Just trying to keep separate things separate here. Also keep in mind linux-user. There's no concept of a machine there, but there's a cpu_copy() function used for forking that tries to re-create the CPU based on its model. So currently cpu_*_init(env->cpu_model_str) needs to be able to recreate an identical CPU through the central code path, without access to a QEMUMachine. (I'd really like to fix this "reentrancy" but we can't just trivially memcpy().) Andreas -- SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Mon, Mar 12, 2012 at 04:49:47PM +0100, Andreas Färber wrote: > Am 11.03.2012 17:16, schrieb Gleb Natapov: > > On Sun, Mar 11, 2012 at 10:33:15AM -0500, Anthony Liguori wrote: > >> On 03/11/2012 09:56 AM, Gleb Natapov wrote: > >>> On Sun, Mar 11, 2012 at 09:12:58AM -0500, Anthony Liguori wrote: > -cpu best wouldn't solve this. You need a read/write configuration > file where QEMU probes the available CPU and records it to be used > for the lifetime of the VM. > >>> That what I thought too, but this shouldn't be the case (Avi's idea). > >>> We need two things: 1) CPU model config should be per machine type. > >>> 2) QEMU should refuse to start if it cannot create cpu exactly as > >>> specified by model config. > >> > >> This would either mean: > >> > >> A. pc-1.1 uses -cpu best with a fixed mask for 1.1 > >> > >> B. pc-1.1 hardcodes Westmere or some other family > >> > > This would mean neither A nor B. May be it wasn't clear but I didn't talk > > about -cpu best above. I am talking about any CPU model with fixed meaning > > (not host or best which are host cpu dependant). Lets take Nehalem for > > example (just to move from Westmere :)). Currently it has level=2. Eduardo > > wants to fix it to be 11, but old guests, installed with -cpu Nehalem, > > should see the same CPU exactly. How do you do it? Have different > > Nehalem definition for pc-1.0 (which level=2) and pc-1.1 (with level=11). > > Lets get back to Westmere. It actually has level=11, but that's only > > expose another problem. Kernel 3.3 and qemu-1.1 combo will support > > architectural PMU which is exposed in cpuid leaf 10. We do not want > > guests installed with -cpu Westmere and qemu-1.0 to see architectural > > PMU after upgrade. How do you do it? Have different Westmere definitions > > for pc-1.0 (does not report PMU) and pc-1.1 (reports PMU). What happens > > if you'll try to run qemu-1.1 -cpu Westmere on Kernel < 3.3 (without > > PMU support)? Qemu will fail to start. > > This sounds pretty much like what Liu Jinsong and Jan are discussing in > the TSC thread on qemu-devel. (cc'ing) I'll look for that thread. Thanks! > > IMO interpreting an explicit -cpu parameter depending on -M would be > wrong. Changing the default CPU based on -M is fine with me. For an > explicit argument we would need Westmere-1.0 analog to pc-1.0. Then the > user gets what the user asks for, without unexpected magic. It is not unexpected magic. It would be a documented mechanism: "-cpu Nehalem-1.0" and "-cpu Nehalem-1.1" would have the same meaning every time, with any machine-type, but "-cpu Nehalem" would be an alias, whose meaning depends on the machine-type. Otherwise we would be stuck with a broken "Nehalem" model forever, and we don't want that. > Note that on my qom-cpu-wip branch [1] (that I hope to have cleaned up > and sent out by tomorrow), all built-in CPUs become statically > registered QOM types. The external definitions that get passed in via > -cpudef become dynamically registered QOM types; I took care to allow > overriding existing classes with the specified -cpudef fields (but > untested). Setting family, level, etc. for -cpu is done on the X86CPU > object instance. [2] > What I don't have yet are QOM properties to set the fields from, e.g., > machine code, but those should be fairly easy to add. Sounds interesting. I will have to take a look at the code to understand how it affects what's being discussed in this thread. > > Andreas > > [1] http://repo.or.cz/w/qemu/afaerber.git/shortlog/refs/heads/qom-cpu-wip > > [2] > http://repo.or.cz/w/qemu/afaerber.git/commit/8a6ede101a2722b790489989f21cad38d3e41fb5 > > -- > SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany > GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg -- Eduardo -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
Am 10.03.2012 19:24, schrieb Anthony Liguori: > Humans probably do one of two things: 1) no cpu option or 2) -cpu host. > > So then why are you introducing -cpu Westmere? [...] > P.S. I spent 30 minutes the other day helping a user who was attempting > to figure out whether his processor was a Conroe, Penryn, etc. Making > this determination is fairly difficult and it makes me wonder whether > having CPU code names is even the best interface for oVirt.. That's why Alex suggested -cpu best, which goes through all those definitions whatever their name and chooses the closest one IIUC. http://patchwork.ozlabs.org/patch/134955/ Andreas -- SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
Am 11.03.2012 17:16, schrieb Gleb Natapov: > On Sun, Mar 11, 2012 at 10:33:15AM -0500, Anthony Liguori wrote: >> On 03/11/2012 09:56 AM, Gleb Natapov wrote: >>> On Sun, Mar 11, 2012 at 09:12:58AM -0500, Anthony Liguori wrote: -cpu best wouldn't solve this. You need a read/write configuration file where QEMU probes the available CPU and records it to be used for the lifetime of the VM. >>> That what I thought too, but this shouldn't be the case (Avi's idea). >>> We need two things: 1) CPU model config should be per machine type. >>> 2) QEMU should refuse to start if it cannot create cpu exactly as >>> specified by model config. >> >> This would either mean: >> >> A. pc-1.1 uses -cpu best with a fixed mask for 1.1 >> >> B. pc-1.1 hardcodes Westmere or some other family >> > This would mean neither A nor B. May be it wasn't clear but I didn't talk > about -cpu best above. I am talking about any CPU model with fixed meaning > (not host or best which are host cpu dependant). Lets take Nehalem for > example (just to move from Westmere :)). Currently it has level=2. Eduardo > wants to fix it to be 11, but old guests, installed with -cpu Nehalem, > should see the same CPU exactly. How do you do it? Have different > Nehalem definition for pc-1.0 (which level=2) and pc-1.1 (with level=11). > Lets get back to Westmere. It actually has level=11, but that's only > expose another problem. Kernel 3.3 and qemu-1.1 combo will support > architectural PMU which is exposed in cpuid leaf 10. We do not want > guests installed with -cpu Westmere and qemu-1.0 to see architectural > PMU after upgrade. How do you do it? Have different Westmere definitions > for pc-1.0 (does not report PMU) and pc-1.1 (reports PMU). What happens > if you'll try to run qemu-1.1 -cpu Westmere on Kernel < 3.3 (without > PMU support)? Qemu will fail to start. This sounds pretty much like what Liu Jinsong and Jan are discussing in the TSC thread on qemu-devel. (cc'ing) IMO interpreting an explicit -cpu parameter depending on -M would be wrong. Changing the default CPU based on -M is fine with me. For an explicit argument we would need Westmere-1.0 analog to pc-1.0. Then the user gets what the user asks for, without unexpected magic. Note that on my qom-cpu-wip branch [1] (that I hope to have cleaned up and sent out by tomorrow), all built-in CPUs become statically registered QOM types. The external definitions that get passed in via -cpudef become dynamically registered QOM types; I took care to allow overriding existing classes with the specified -cpudef fields (but untested). Setting family, level, etc. for -cpu is done on the X86CPU object instance. [2] What I don't have yet are QOM properties to set the fields from, e.g., machine code, but those should be fairly easy to add. Andreas [1] http://repo.or.cz/w/qemu/afaerber.git/shortlog/refs/heads/qom-cpu-wip [2] http://repo.or.cz/w/qemu/afaerber.git/commit/8a6ede101a2722b790489989f21cad38d3e41fb5 -- SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Mon, Mar 12, 2012 at 09:48:11AM -0500, Anthony Liguori wrote: > On 03/11/2012 11:16 AM, Gleb Natapov wrote: > >On Sun, Mar 11, 2012 at 10:33:15AM -0500, Anthony Liguori wrote: > >>On 03/11/2012 09:56 AM, Gleb Natapov wrote: > >>>On Sun, Mar 11, 2012 at 09:12:58AM -0500, Anthony Liguori wrote: > -cpu best wouldn't solve this. You need a read/write configuration > file where QEMU probes the available CPU and records it to be used > for the lifetime of the VM. > >>>That what I thought too, but this shouldn't be the case (Avi's idea). > >>>We need two things: 1) CPU model config should be per machine type. > >>>2) QEMU should refuse to start if it cannot create cpu exactly as > >>>specified by model config. > >> > >>This would either mean: > >> > >>A. pc-1.1 uses -cpu best with a fixed mask for 1.1 > >> > >>B. pc-1.1 hardcodes Westmere or some other family > >> > >This would mean neither A nor B. May be it wasn't clear but I didn't talk > >about -cpu best above. I am talking about any CPU model with fixed meaning > >(not host or best which are host cpu dependant). Lets take Nehalem for > >example (just to move from Westmere :)). Currently it has level=2. Eduardo > >wants to fix it to be 11, but old guests, installed with -cpu Nehalem, > >should see the same CPU exactly. How do you do it? Have different > >Nehalem definition for pc-1.0 (which level=2) and pc-1.1 (with level=11). > >Lets get back to Westmere. It actually has level=11, but that's only > >expose another problem. Kernel 3.3 and qemu-1.1 combo will support > >architectural PMU which is exposed in cpuid leaf 10. We do not want > >guests installed with -cpu Westmere and qemu-1.0 to see architectural > >PMU after upgrade. How do you do it? Have different Westmere definitions > >for pc-1.0 (does not report PMU) and pc-1.1 (reports PMU). What happens > >if you'll try to run qemu-1.1 -cpu Westmere on Kernel< 3.3 (without > >PMU support)? Qemu will fail to start. > > So, you're essentially proposing that -cpu Westmere becomes a machine > option and that we let the machines interpret it as they see fit? > > So --machine pc-1.0,cpu=Westmere would result in something different > than --machine pc-1.1,cpu=Westmere? Exactly. > That's something pretty different than what we're doing today. I > think that we would have a single CPUX86 object and that part of the > pc initialization process was to create an appropriately configured > CPUx86 object. Yes, that's different from what we're doing today, and it has to be fixed. (And, BTW, I'm really worried about your proposal that machine-types would suddenly disappear when using -nodefconfig in case we decide to move machine-type data to an external file one day. Design decisions aside, this would break an interface that management tools already have today.) -- Eduardo -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/11/2012 11:16 AM, Gleb Natapov wrote: On Sun, Mar 11, 2012 at 10:33:15AM -0500, Anthony Liguori wrote: On 03/11/2012 09:56 AM, Gleb Natapov wrote: On Sun, Mar 11, 2012 at 09:12:58AM -0500, Anthony Liguori wrote: -cpu best wouldn't solve this. You need a read/write configuration file where QEMU probes the available CPU and records it to be used for the lifetime of the VM. That what I thought too, but this shouldn't be the case (Avi's idea). We need two things: 1) CPU model config should be per machine type. 2) QEMU should refuse to start if it cannot create cpu exactly as specified by model config. This would either mean: A. pc-1.1 uses -cpu best with a fixed mask for 1.1 B. pc-1.1 hardcodes Westmere or some other family This would mean neither A nor B. May be it wasn't clear but I didn't talk about -cpu best above. I am talking about any CPU model with fixed meaning (not host or best which are host cpu dependant). Lets take Nehalem for example (just to move from Westmere :)). Currently it has level=2. Eduardo wants to fix it to be 11, but old guests, installed with -cpu Nehalem, should see the same CPU exactly. How do you do it? Have different Nehalem definition for pc-1.0 (which level=2) and pc-1.1 (with level=11). Lets get back to Westmere. It actually has level=11, but that's only expose another problem. Kernel 3.3 and qemu-1.1 combo will support architectural PMU which is exposed in cpuid leaf 10. We do not want guests installed with -cpu Westmere and qemu-1.0 to see architectural PMU after upgrade. How do you do it? Have different Westmere definitions for pc-1.0 (does not report PMU) and pc-1.1 (reports PMU). What happens if you'll try to run qemu-1.1 -cpu Westmere on Kernel< 3.3 (without PMU support)? Qemu will fail to start. So, you're essentially proposing that -cpu Westmere becomes a machine option and that we let the machines interpret it as they see fit? So --machine pc-1.0,cpu=Westmere would result in something different than --machine pc-1.1,cpu=Westmere? That's something pretty different than what we're doing today. I think that we would have a single CPUX86 object and that part of the pc initialization process was to create an appropriately configured CPUx86 object. Regards, Anthony Liguori -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Mon, Mar 12, 2012 at 01:55:34PM +, Daniel P. Berrange wrote: > On Mon, Mar 12, 2012 at 03:53:38PM +0200, Gleb Natapov wrote: > > On Mon, Mar 12, 2012 at 01:50:18PM +, Daniel P. Berrange wrote: > > > On Mon, Mar 12, 2012 at 03:15:32PM +0200, Gleb Natapov wrote: > > > > On Mon, Mar 12, 2012 at 01:04:19PM +, Daniel P. Berrange wrote: > > > > > On Mon, Mar 12, 2012 at 09:52:27AM -0300, Eduardo Habkost wrote: > > > > > > On Sun, Mar 11, 2012 at 09:12:58AM -0500, Anthony Liguori wrote: > > > > > > > On 03/11/2012 08:27 AM, Gleb Natapov wrote: > > > > > > > >On Sat, Mar 10, 2012 at 12:24:47PM -0600, Anthony Liguori wrote: > > > > > > > >>Let's step back here. > > > > > > > >> > > > > > > > >>Why are you writing these patches? It's probably not because > > > > > > > >>you > > > > > > > >>have a desire to say -cpu Westmere when you run QEMU on your > > > > > > > >>laptop. > > > > > > > >>I'd wager to say that no human has ever done that or that if > > > > > > > >>they > > > > > > > >>had, they did so by accident because they read documentation and > > > > > > > >>thought they had to. > > > > > > > > > > > > No, it's because libvirt doesn't handle all the tiny small details > > > > > > involved in specifying a CPU. All libvirty knows about are a set of > > > > > > CPU > > > > > > flag bits, but it knows nothing about 'level', 'family', and > > > > > > 'xlevel', > > > > > > but we would like to allow it to expose a Westmere-like CPU to the > > > > > > guest. > > > > > > > > > > This is easily fixable in libvirt - so for the point of going > > > > > discussion, > > > > > IMHO, we can assume libvirt will support level, family, xlevel, etc. > > > > > > > > > And fill in all cpuid leafs by querying /dev/kvm when needed or, if TCG > > > > is used, replicating QEMU logic? And since QEMU should be usable without > > > > libvirt the same logic should be implemented in QEMU anyway. > > > > > > I'm not refering to that. I'm saying that any data QEMU has in its > > > config file (/etc/qemu/target-x86_64.conf) should be represented > > > in the libvirt CPU XML. family, model, stepping, xlevel and > > > model_id are currently in QEMU CPU configs, but not in libvirt XML, > > > which is something we will fix. The other issues you mention are > > > completely independant of that. > > > > > Eduardo is going to extend what can be configured in > > /etc/qemu/target-x86_64.conf > > and make CPU models name per machine type. What QEMU has now is not > > good enough. I doubt libvirt goal is to be as bad as QEMU :) > > Of course not - libvirt will obviously be extended to cope with this > too > So you goal is to follow closely what QEMU does? Fine by me, but then QEMU design decisions in this ares should not rely on libvirt (as in "this is libvirt job"). -- Gleb. -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Mon, Mar 12, 2012 at 03:53:38PM +0200, Gleb Natapov wrote: > On Mon, Mar 12, 2012 at 01:50:18PM +, Daniel P. Berrange wrote: > > On Mon, Mar 12, 2012 at 03:15:32PM +0200, Gleb Natapov wrote: > > > On Mon, Mar 12, 2012 at 01:04:19PM +, Daniel P. Berrange wrote: > > > > On Mon, Mar 12, 2012 at 09:52:27AM -0300, Eduardo Habkost wrote: > > > > > On Sun, Mar 11, 2012 at 09:12:58AM -0500, Anthony Liguori wrote: > > > > > > On 03/11/2012 08:27 AM, Gleb Natapov wrote: > > > > > > >On Sat, Mar 10, 2012 at 12:24:47PM -0600, Anthony Liguori wrote: > > > > > > >>Let's step back here. > > > > > > >> > > > > > > >>Why are you writing these patches? It's probably not because you > > > > > > >>have a desire to say -cpu Westmere when you run QEMU on your > > > > > > >>laptop. > > > > > > >>I'd wager to say that no human has ever done that or that if they > > > > > > >>had, they did so by accident because they read documentation and > > > > > > >>thought they had to. > > > > > > > > > > No, it's because libvirt doesn't handle all the tiny small details > > > > > involved in specifying a CPU. All libvirty knows about are a set of > > > > > CPU > > > > > flag bits, but it knows nothing about 'level', 'family', and 'xlevel', > > > > > but we would like to allow it to expose a Westmere-like CPU to the > > > > > guest. > > > > > > > > This is easily fixable in libvirt - so for the point of going > > > > discussion, > > > > IMHO, we can assume libvirt will support level, family, xlevel, etc. > > > > > > > And fill in all cpuid leafs by querying /dev/kvm when needed or, if TCG > > > is used, replicating QEMU logic? And since QEMU should be usable without > > > libvirt the same logic should be implemented in QEMU anyway. > > > > I'm not refering to that. I'm saying that any data QEMU has in its > > config file (/etc/qemu/target-x86_64.conf) should be represented > > in the libvirt CPU XML. family, model, stepping, xlevel and > > model_id are currently in QEMU CPU configs, but not in libvirt XML, > > which is something we will fix. The other issues you mention are > > completely independant of that. > > > Eduardo is going to extend what can be configured in > /etc/qemu/target-x86_64.conf > and make CPU models name per machine type. What QEMU has now is not > good enough. I doubt libvirt goal is to be as bad as QEMU :) Of course not - libvirt will obviously be extended to cope with this too Daniel -- |: http://berrange.com -o-http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :| -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Mon, Mar 12, 2012 at 01:50:18PM +, Daniel P. Berrange wrote: > On Mon, Mar 12, 2012 at 03:15:32PM +0200, Gleb Natapov wrote: > > On Mon, Mar 12, 2012 at 01:04:19PM +, Daniel P. Berrange wrote: > > > On Mon, Mar 12, 2012 at 09:52:27AM -0300, Eduardo Habkost wrote: > > > > On Sun, Mar 11, 2012 at 09:12:58AM -0500, Anthony Liguori wrote: > > > > > On 03/11/2012 08:27 AM, Gleb Natapov wrote: > > > > > >On Sat, Mar 10, 2012 at 12:24:47PM -0600, Anthony Liguori wrote: > > > > > >>Let's step back here. > > > > > >> > > > > > >>Why are you writing these patches? It's probably not because you > > > > > >>have a desire to say -cpu Westmere when you run QEMU on your laptop. > > > > > >>I'd wager to say that no human has ever done that or that if they > > > > > >>had, they did so by accident because they read documentation and > > > > > >>thought they had to. > > > > > > > > No, it's because libvirt doesn't handle all the tiny small details > > > > involved in specifying a CPU. All libvirty knows about are a set of CPU > > > > flag bits, but it knows nothing about 'level', 'family', and 'xlevel', > > > > but we would like to allow it to expose a Westmere-like CPU to the > > > > guest. > > > > > > This is easily fixable in libvirt - so for the point of going discussion, > > > IMHO, we can assume libvirt will support level, family, xlevel, etc. > > > > > And fill in all cpuid leafs by querying /dev/kvm when needed or, if TCG > > is used, replicating QEMU logic? And since QEMU should be usable without > > libvirt the same logic should be implemented in QEMU anyway. > > I'm not refering to that. I'm saying that any data QEMU has in its > config file (/etc/qemu/target-x86_64.conf) should be represented > in the libvirt CPU XML. family, model, stepping, xlevel and > model_id are currently in QEMU CPU configs, but not in libvirt XML, > which is something we will fix. The other issues you mention are > completely independant of that. > Eduardo is going to extend what can be configured in /etc/qemu/target-x86_64.conf and make CPU models name per machine type. What QEMU has now is not good enough. I doubt libvirt goal is to be as bad as QEMU :) -- Gleb. -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Mon, Mar 12, 2012 at 03:15:32PM +0200, Gleb Natapov wrote: > On Mon, Mar 12, 2012 at 01:04:19PM +, Daniel P. Berrange wrote: > > On Mon, Mar 12, 2012 at 09:52:27AM -0300, Eduardo Habkost wrote: > > > On Sun, Mar 11, 2012 at 09:12:58AM -0500, Anthony Liguori wrote: > > > > On 03/11/2012 08:27 AM, Gleb Natapov wrote: > > > > >On Sat, Mar 10, 2012 at 12:24:47PM -0600, Anthony Liguori wrote: > > > > >>Let's step back here. > > > > >> > > > > >>Why are you writing these patches? It's probably not because you > > > > >>have a desire to say -cpu Westmere when you run QEMU on your laptop. > > > > >>I'd wager to say that no human has ever done that or that if they > > > > >>had, they did so by accident because they read documentation and > > > > >>thought they had to. > > > > > > No, it's because libvirt doesn't handle all the tiny small details > > > involved in specifying a CPU. All libvirty knows about are a set of CPU > > > flag bits, but it knows nothing about 'level', 'family', and 'xlevel', > > > but we would like to allow it to expose a Westmere-like CPU to the > > > guest. > > > > This is easily fixable in libvirt - so for the point of going discussion, > > IMHO, we can assume libvirt will support level, family, xlevel, etc. > > > And fill in all cpuid leafs by querying /dev/kvm when needed or, if TCG > is used, replicating QEMU logic? And since QEMU should be usable without > libvirt the same logic should be implemented in QEMU anyway. I'm not refering to that. I'm saying that any data QEMU has in its config file (/etc/qemu/target-x86_64.conf) should be represented in the libvirt CPU XML. family, model, stepping, xlevel and model_id are currently in QEMU CPU configs, but not in libvirt XML, which is something we will fix. The other issues you mention are completely independant of that. Regards, Daniel -- |: http://berrange.com -o-http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :| -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Mon, Mar 12, 2012 at 10:32:21AM -0300, Eduardo Habkost wrote: > On Mon, Mar 12, 2012 at 03:15:32PM +0200, Gleb Natapov wrote: > > On Mon, Mar 12, 2012 at 01:04:19PM +, Daniel P. Berrange wrote: > > > On Mon, Mar 12, 2012 at 09:52:27AM -0300, Eduardo Habkost wrote: > > > > On Sun, Mar 11, 2012 at 09:12:58AM -0500, Anthony Liguori wrote: > > > > > On 03/11/2012 08:27 AM, Gleb Natapov wrote: > > > > > >On Sat, Mar 10, 2012 at 12:24:47PM -0600, Anthony Liguori wrote: > > > > > >>Let's step back here. > > > > > >> > > > > > >>Why are you writing these patches? It's probably not because you > > > > > >>have a desire to say -cpu Westmere when you run QEMU on your laptop. > > > > > >>I'd wager to say that no human has ever done that or that if they > > > > > >>had, they did so by accident because they read documentation and > > > > > >>thought they had to. > > > > > > > > No, it's because libvirt doesn't handle all the tiny small details > > > > involved in specifying a CPU. All libvirty knows about are a set of CPU > > > > flag bits, but it knows nothing about 'level', 'family', and 'xlevel', > > > > but we would like to allow it to expose a Westmere-like CPU to the > > > > guest. > > > > > > This is easily fixable in libvirt - so for the point of going discussion, > > > IMHO, we can assume libvirt will support level, family, xlevel, etc. > > > > > And fill in all cpuid leafs by querying /dev/kvm when needed or, if TCG > > is used, replicating QEMU logic? And since QEMU should be usable without > > libvirt the same logic should be implemented in QEMU anyway. > > To implement this properly, libvirt will need a proper probing interface > to know what exactly is available and can be enabled. I plan to > implement that. > > I am have no problem in giving to libvirt the power to shoot itself in > the foot. I believe libvirt developers can handle that. I have a problem > with requiring every user (human or machine) to handle a weapon that can > shoot their foot (that means, requiring the user to write the CPU model > definition from scratch, or requiring the user to blindly copy&paste the > default config file). > You are dangerous person Eduardo! -- Gleb. -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Mon, Mar 12, 2012 at 03:15:32PM +0200, Gleb Natapov wrote: > On Mon, Mar 12, 2012 at 01:04:19PM +, Daniel P. Berrange wrote: > > On Mon, Mar 12, 2012 at 09:52:27AM -0300, Eduardo Habkost wrote: > > > On Sun, Mar 11, 2012 at 09:12:58AM -0500, Anthony Liguori wrote: > > > > On 03/11/2012 08:27 AM, Gleb Natapov wrote: > > > > >On Sat, Mar 10, 2012 at 12:24:47PM -0600, Anthony Liguori wrote: > > > > >>Let's step back here. > > > > >> > > > > >>Why are you writing these patches? It's probably not because you > > > > >>have a desire to say -cpu Westmere when you run QEMU on your laptop. > > > > >>I'd wager to say that no human has ever done that or that if they > > > > >>had, they did so by accident because they read documentation and > > > > >>thought they had to. > > > > > > No, it's because libvirt doesn't handle all the tiny small details > > > involved in specifying a CPU. All libvirty knows about are a set of CPU > > > flag bits, but it knows nothing about 'level', 'family', and 'xlevel', > > > but we would like to allow it to expose a Westmere-like CPU to the > > > guest. > > > > This is easily fixable in libvirt - so for the point of going discussion, > > IMHO, we can assume libvirt will support level, family, xlevel, etc. > > > And fill in all cpuid leafs by querying /dev/kvm when needed or, if TCG > is used, replicating QEMU logic? And since QEMU should be usable without > libvirt the same logic should be implemented in QEMU anyway. To implement this properly, libvirt will need a proper probing interface to know what exactly is available and can be enabled. I plan to implement that. I am have no problem in giving to libvirt the power to shoot itself in the foot. I believe libvirt developers can handle that. I have a problem with requiring every user (human or machine) to handle a weapon that can shoot their foot (that means, requiring the user to write the CPU model definition from scratch, or requiring the user to blindly copy&paste the default config file). -- Eduardo -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Mon, Mar 12, 2012 at 01:04:19PM +, Daniel P. Berrange wrote: > On Mon, Mar 12, 2012 at 09:52:27AM -0300, Eduardo Habkost wrote: > > On Sun, Mar 11, 2012 at 09:12:58AM -0500, Anthony Liguori wrote: > > > On 03/11/2012 08:27 AM, Gleb Natapov wrote: > > > >On Sat, Mar 10, 2012 at 12:24:47PM -0600, Anthony Liguori wrote: > > > >>Let's step back here. > > > >> > > > >>Why are you writing these patches? It's probably not because you > > > >>have a desire to say -cpu Westmere when you run QEMU on your laptop. > > > >>I'd wager to say that no human has ever done that or that if they > > > >>had, they did so by accident because they read documentation and > > > >>thought they had to. > > > > No, it's because libvirt doesn't handle all the tiny small details > > involved in specifying a CPU. All libvirty knows about are a set of CPU > > flag bits, but it knows nothing about 'level', 'family', and 'xlevel', > > but we would like to allow it to expose a Westmere-like CPU to the > > guest. > > This is easily fixable in libvirt - so for the point of going discussion, > IMHO, we can assume libvirt will support level, family, xlevel, etc. > And fill in all cpuid leafs by querying /dev/kvm when needed or, if TCG is used, replicating QEMU logic? And since QEMU should be usable without libvirt the same logic should be implemented in QEMU anyway. -- Gleb. -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Sun, Mar 11, 2012 at 10:41:32AM -0500, Anthony Liguori wrote: > On 03/11/2012 10:12 AM, Gleb Natapov wrote: > >On Sun, Mar 11, 2012 at 09:16:49AM -0500, Anthony Liguori wrote: > >>>If libvirt assumes anything about what kvm actually supports it is > >>>working only by sheer luck. > >> > >>Well the simple answer for libvirt is don't use -nodefconfig and > >>then it can reuse the CPU definitions (including any that the user > >>adds). > >CPU models should be usable even with -nodefconfig. CPU model is more > >like device. By -cpu Nehalem I am saying I want Nehalem device in my > >machine. > > Let's say we moved CPU definitions to /usr/share/qemu/cpu-models.xml. > > Obviously, we'd want a command line option to be able to change that > location so we'd introduce -cpu-models PATH. > > But we want all of our command line options to be settable by the > global configuration file so we would have a cpu-model=PATH to the > configuration file. > > But why hard code a path when we can just set the default path in the > configuration file so let's avoid hard coding and just put > cpu-models=/usr/share/qemu/cpu-models.xml in the default > configuration file. We wouldn't do the above. -nodefconfig should disable the loading of files on /etc, but it shouldn't disable loading internal non-configurable data that we just happened to choose to store outside the qemu binary because it makes development easier. Really, the requirement of a "default configuration file" is a problem by itself. Qemu should not require a default configuration file to work, and it shouldn't require users to copy the default configuration file to change options from the default. Doing this would make it impossible to deploy fixes to users if we evern find out that the default configuration file had a serious bug. What if a bug in our default configuration file has a serious security implication? > > But now when libvirt uses -nodefconfig, those models go away. > -nodefconfig means start QEMU in the most minimal state possible. > You get what you pay for if you use it. > > We'll have the same problem with machine configuration files. At > some point in time, -nodefconfig will make machine models disappear. It shouldn't. Machine-types are defaults to be used as base, they are not user-provided configuration. And the fact that we decided to store some data outside of the Qemu binary is orthogonal the design decisions in the Qemu command-line and configuration interface. As I said previously, requiring generation of opaque config files (and "copy the default config file and change it" is included on my definition of "generation of opaque config files") is poor design, IMO. I bet this even has an entry in some design anti-pattern catalog somewhere. -- Eduardo -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Mon, Mar 12, 2012 at 09:52:27AM -0300, Eduardo Habkost wrote: > On Sun, Mar 11, 2012 at 09:12:58AM -0500, Anthony Liguori wrote: > > On 03/11/2012 08:27 AM, Gleb Natapov wrote: > > >On Sat, Mar 10, 2012 at 12:24:47PM -0600, Anthony Liguori wrote: > > >>Let's step back here. > > >> > > >>Why are you writing these patches? It's probably not because you > > >>have a desire to say -cpu Westmere when you run QEMU on your laptop. > > >>I'd wager to say that no human has ever done that or that if they > > >>had, they did so by accident because they read documentation and > > >>thought they had to. > > No, it's because libvirt doesn't handle all the tiny small details > involved in specifying a CPU. All libvirty knows about are a set of CPU > flag bits, but it knows nothing about 'level', 'family', and 'xlevel', > but we would like to allow it to expose a Westmere-like CPU to the > guest. This is easily fixable in libvirt - so for the point of going discussion, IMHO, we can assume libvirt will support level, family, xlevel, etc. Daniel -- |: http://berrange.com -o-http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :| -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Sun, Mar 11, 2012 at 09:12:58AM -0500, Anthony Liguori wrote: > On 03/11/2012 08:27 AM, Gleb Natapov wrote: > >On Sat, Mar 10, 2012 at 12:24:47PM -0600, Anthony Liguori wrote: > >>Let's step back here. > >> > >>Why are you writing these patches? It's probably not because you > >>have a desire to say -cpu Westmere when you run QEMU on your laptop. > >>I'd wager to say that no human has ever done that or that if they > >>had, they did so by accident because they read documentation and > >>thought they had to. No, it's because libvirt doesn't handle all the tiny small details involved in specifying a CPU. All libvirty knows about are a set of CPU flag bits, but it knows nothing about 'level', 'family', and 'xlevel', but we would like to allow it to expose a Westmere-like CPU to the guest. libvirt does know how to use the Westmere CPU model today, if it is not disabled by -nodefconfig. The interface it uses for probing has deficiencies, but it works right now. > >>Humans probably do one of two things: 1) no cpu option or 2) -cpu host. > >> > >And both are not optimal. Actually both are bad. First one because > >default cpu is very conservative and the second because there is no > >guaranty that guest will continue to work after qemu or kernel upgrade. > > > >Let me elaborate about the later. Suppose host CPU has kill_guest > >feature and at the time a guest was installed it was not implemented by > >kvm. Since it was not implemented by kvm it was not present in vcpu > >during installation and the guest didn't install "workaround kill_guest" > >module. Now unsuspecting user upgrades the kernel and tries to restart > >the guest and fails. He writes angry letter to qemu-devel and is asked to > >reinstall his guest and move along. > > -cpu best wouldn't solve this. You need a read/write configuration > file where QEMU probes the available CPU and records it to be used > for the lifetime of the VM. If the CPU records are used for probing, this is yet another reason they are not "configuration", but "defaults/templates to be used to build the actual configuration". IMHO, having to generate an opaque config file based on the results of probing is poor interface design, for humans _and_ for machines. If we have any bug on the probing, or on the data used as base for the probing, or on the config generation, it will be impossible to deploy a fix for the users. This is why machine-types exist: you have the ability to implement probing and/or sane defaults, but at the same time you can change the probing behavior or the set of defaults without breaking existing machines. This way, the config file contains only what the user really wanted to configure, not some complex and opaque result of a probing process. Tthe fact that we have a _set_ of CPU definitions to choose from (or to use as input for probing) instead of a single default "CPU" definition that the user can change is a sign that that the cpudefs are _not_ user configuration, but just templates/defaults. [...] > This discussion isn't about whether QEMU should have a Westmere > processor definition. In fact, I think I already applied that patch. > > It's a discussion about how we handle this up and down the stack. Agreed on this point. > > The question is who should define and manage CPU compatibility. > Right now QEMU does to a certain degree, libvirt discards this and > does it's own thing, and VDSM/ovirt-engine assume that we're > providing something and has built a UI around it. libvirt doesn't discard this. If it just discarded this and properly defined its own models, I wouldn't even have (re-)started this thread. (Well, maybe I would have started a similar thread arguing that we are wasting time working on equivalent known-to-work CPU model definitions on Qemu and libvirt. Today we don't waste time doing it because libvirt currently expects -nodefconfig to not disable the existing default models). > > What I'm proposing we consider: have VDSM manage CPU definitions in > order to provide a specific user experience in ovirt-engine. I don't disagree completely with that. The problem is defining what's "CPU definitions". The current cpudef semantics is simply too low level, it impacts other features that are _already_ managed by Qemu. Let me try to enumerate: - Some CPUID leafs are defined based on -smp; - Some CPUID leafs depend on kernel capabilities; - The availability of some CPUID leafs depend on some features being enabled or not, but they are simply not exposed if a proper 'level' value is set. We could have two approaches here: we can define some details of CPU definitions as "not configurable" and others as "must-be configurable", and force management layer to agree with us about what should be configurable or not. Or, we could simply define that a sane set of CPU definitions are part of a machine-type, and let managment to reconfigure parts of it if desired, but do not force it to configure it if not needed. > > We wo
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Sun, Mar 11, 2012 at 10:41:32AM -0500, Anthony Liguori wrote: > On 03/11/2012 10:12 AM, Gleb Natapov wrote: > >On Sun, Mar 11, 2012 at 09:16:49AM -0500, Anthony Liguori wrote: > >>>If libvirt assumes anything about what kvm actually supports it is > >>>working only by sheer luck. > >> > >>Well the simple answer for libvirt is don't use -nodefconfig and > >>then it can reuse the CPU definitions (including any that the user > >>adds). > >CPU models should be usable even with -nodefconfig. CPU model is more > >like device. By -cpu Nehalem I am saying I want Nehalem device in my > >machine. > > Let's say we moved CPU definitions to /usr/share/qemu/cpu-models.xml. > > Obviously, we'd want a command line option to be able to change that > location so we'd introduce -cpu-models PATH. > > But we want all of our command line options to be settable by the > global configuration file so we would have a cpu-model=PATH to the > configuration file. > > But why hard code a path when we can just set the default path in > the configuration file so let's avoid hard coding and just put > cpu-models=/usr/share/qemu/cpu-models.xml in the default > configuration file. > We have two places where we define cpu models: hardcoded in target-i386/cpuid.c and in target-x86_64.conf. We moved them out to conf file because this way it is easier to add, update, examine compare CPU models. But they still should be treated as essential part of qemu. Given this I do not see the step above as a logical one. CPU models are not part of machine config. "-cpu Nehalem,-sse,level=3,model=5" is part of machine config. What if we introduce a way to write devices in LUA. Should -nodefconfig drop devices implemented as LUA scripts too? > But now when libvirt uses -nodefconfig, those models go away. > -nodefconfig means start QEMU in the most minimal state possible. > You get what you pay for if you use it. > > We'll have the same problem with machine configuration files. At > some point in time, -nodefconfig will make machine models disappear. > -- Gleb. -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Sun, Mar 11, 2012 at 10:33:15AM -0500, Anthony Liguori wrote: > On 03/11/2012 09:56 AM, Gleb Natapov wrote: > >On Sun, Mar 11, 2012 at 09:12:58AM -0500, Anthony Liguori wrote: > >>-cpu best wouldn't solve this. You need a read/write configuration > >>file where QEMU probes the available CPU and records it to be used > >>for the lifetime of the VM. > >That what I thought too, but this shouldn't be the case (Avi's idea). > >We need two things: 1) CPU model config should be per machine type. > >2) QEMU should refuse to start if it cannot create cpu exactly as > >specified by model config. > > This would either mean: > > A. pc-1.1 uses -cpu best with a fixed mask for 1.1 > > B. pc-1.1 hardcodes Westmere or some other family > This would mean neither A nor B. May be it wasn't clear but I didn't talk about -cpu best above. I am talking about any CPU model with fixed meaning (not host or best which are host cpu dependant). Lets take Nehalem for example (just to move from Westmere :)). Currently it has level=2. Eduardo wants to fix it to be 11, but old guests, installed with -cpu Nehalem, should see the same CPU exactly. How do you do it? Have different Nehalem definition for pc-1.0 (which level=2) and pc-1.1 (with level=11). Lets get back to Westmere. It actually has level=11, but that's only expose another problem. Kernel 3.3 and qemu-1.1 combo will support architectural PMU which is exposed in cpuid leaf 10. We do not want guests installed with -cpu Westmere and qemu-1.0 to see architectural PMU after upgrade. How do you do it? Have different Westmere definitions for pc-1.0 (does not report PMU) and pc-1.1 (reports PMU). What happens if you'll try to run qemu-1.1 -cpu Westmere on Kernel < 3.3 (without PMU support)? Qemu will fail to start. > (A) would imply a different CPU if you moved the machine from one > system to another. I would think this would be very problematic > from a user's perspective. > > (B) would imply that we had to choose the least common denominator > which is essentially what we do today with qemu64. If you want to > just switch qemu64 to Conroe, I don't think that's a huge difference > from what we have today. > > >>It's a discussion about how we handle this up and down the stack. > >> > >>The question is who should define and manage CPU compatibility. > >>Right now QEMU does to a certain degree, libvirt discards this and > >>does it's own thing, and VDSM/ovirt-engine assume that we're > >>providing something and has built a UI around it. > >If we want QEMU to be usable without management layer then QEMU should > >provide stable CPU models. Stable in a sense that qemu, kernel or CPU > >upgrade does not change what guest sees. > > We do this today by exposing -cpu qemu64 by default. If all you're > advocating is doing -cpu Conroe by default, that's fine. I am not advocating that. I am saying we should be able to amend qemu64 definition without breaking older guests that use it. > > But I fail to see where this fits into the larger discussion here. > The problem to solve is: I want to use the largest possible subset > of CPU features available uniformly throughout my datacenter. > > QEMU and libvirt have single node views so they cannot solve this > problem on their own. Whether that subset is a generic > Westmere-like processor that never existed IRL or a specific > Westmere processor seems like a decision that should be made by the > datacenter level manager with the node level view. > > If I have a homogeneous environments of Xeon 7540, I would probably > like to see a Xeon 7540 in my guest. Doesn't it make sense to > enable the management tool to make this decision? > Of course neither QEMU nor libvirt can't made a cluster wide decision. If QEMU provides sane CPU model definitions (usable even with -nodefconfig) it would be always possible to find the model that fits best. If the oldest CPU in data center is Nehalem then probably -cpu Nehalem will do. But our CPU model definitions have a lot of shortcomings and we were talking with Edurado how to fix them when he brought this thread back to life, so may be I stirred the discussion a little bit in the wrong direction, but I do think those things are connected. If QEMU CPU model definitions are not stable across upgrades how can we say to management that it is safe to use them? Instead they insist in reimplementing the same logic in mngmt layer and do it badly (because the lack of info). -- Gleb. -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/11/2012 10:12 AM, Gleb Natapov wrote: On Sun, Mar 11, 2012 at 09:16:49AM -0500, Anthony Liguori wrote: If libvirt assumes anything about what kvm actually supports it is working only by sheer luck. Well the simple answer for libvirt is don't use -nodefconfig and then it can reuse the CPU definitions (including any that the user adds). CPU models should be usable even with -nodefconfig. CPU model is more like device. By -cpu Nehalem I am saying I want Nehalem device in my machine. Let's say we moved CPU definitions to /usr/share/qemu/cpu-models.xml. Obviously, we'd want a command line option to be able to change that location so we'd introduce -cpu-models PATH. But we want all of our command line options to be settable by the global configuration file so we would have a cpu-model=PATH to the configuration file. But why hard code a path when we can just set the default path in the configuration file so let's avoid hard coding and just put cpu-models=/usr/share/qemu/cpu-models.xml in the default configuration file. But now when libvirt uses -nodefconfig, those models go away. -nodefconfig means start QEMU in the most minimal state possible. You get what you pay for if you use it. We'll have the same problem with machine configuration files. At some point in time, -nodefconfig will make machine models disappear. Regards, Anthony Liguori -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/11/2012 09:56 AM, Gleb Natapov wrote: On Sun, Mar 11, 2012 at 09:12:58AM -0500, Anthony Liguori wrote: -cpu best wouldn't solve this. You need a read/write configuration file where QEMU probes the available CPU and records it to be used for the lifetime of the VM. That what I thought too, but this shouldn't be the case (Avi's idea). We need two things: 1) CPU model config should be per machine type. 2) QEMU should refuse to start if it cannot create cpu exactly as specified by model config. This would either mean: A. pc-1.1 uses -cpu best with a fixed mask for 1.1 B. pc-1.1 hardcodes Westmere or some other family (A) would imply a different CPU if you moved the machine from one system to another. I would think this would be very problematic from a user's perspective. (B) would imply that we had to choose the least common denominator which is essentially what we do today with qemu64. If you want to just switch qemu64 to Conroe, I don't think that's a huge difference from what we have today. It's a discussion about how we handle this up and down the stack. The question is who should define and manage CPU compatibility. Right now QEMU does to a certain degree, libvirt discards this and does it's own thing, and VDSM/ovirt-engine assume that we're providing something and has built a UI around it. If we want QEMU to be usable without management layer then QEMU should provide stable CPU models. Stable in a sense that qemu, kernel or CPU upgrade does not change what guest sees. We do this today by exposing -cpu qemu64 by default. If all you're advocating is doing -cpu Conroe by default, that's fine. But I fail to see where this fits into the larger discussion here. The problem to solve is: I want to use the largest possible subset of CPU features available uniformly throughout my datacenter. QEMU and libvirt have single node views so they cannot solve this problem on their own. Whether that subset is a generic Westmere-like processor that never existed IRL or a specific Westmere processor seems like a decision that should be made by the datacenter level manager with the node level view. If I have a homogeneous environments of Xeon 7540, I would probably like to see a Xeon 7540 in my guest. Doesn't it make sense to enable the management tool to make this decision? Regards, Anthony Liguori -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Sun, Mar 11, 2012 at 09:16:49AM -0500, Anthony Liguori wrote: > >If libvirt assumes anything about what kvm actually supports it is > >working only by sheer luck. > > Well the simple answer for libvirt is don't use -nodefconfig and > then it can reuse the CPU definitions (including any that the user > adds). CPU models should be usable even with -nodefconfig. CPU model is more like device. By -cpu Nehalem I am saying I want Nehalem device in my machine. > > Really, what's the point of having a layer of management if we're > saying that doing policy management is too complicated for that > layer? What does that layer exist to provide then? > I was always against libvirt configuring low level details of CPU. What it should do IMO is to chose best CPU model for host cpu (one can argue that fiddling with /proc/cpuinfo is not QEMU busyness). > >>(Also, there are additional low-level bits that really have to be > >>maintained somewhere, just to have sane defaults. Currently many CPUID > >>leafs are exposed to the guest without letting the user control them, > >>and worse: without keeping stability of guest-visible bits when > >>upgrading Qemu or the host kernel. And that's what machine-types are > >>for: to have sane defaults to be used as base.) > >> > >>Let me give you a practical example: I had a bug report about improper > >>CPU topology information[1]. After investigating it, I have found out > >>that the "level" cpudef field is too low; CPU core topology information > >>is provided on CPUID leaf 4, and most of the Intel CPU models on Qemu > >>have level=2 today (I don't know why). So, Qemu is responsible for > >>exposing CPU topology information set using '-smp' to the guest OS, but > >>libvirt would have to be responsible for choosing a proper "level" value > >>that makes that information visible to the guest. We can _allow_ libvirt > >>to fiddle with these low-level bits, of course, but requiring every > >>management layer to build this low-level information from scratch is > >>just a recipe to waste developer time. > >And QEMU become even less usable from a command line. One more point to > >kvm-tool I guess. > > I'm not sure what your point is. We're talking about an option that > humans don't use. How is this a discussion about QEMU usability? > If for a user to have stable guest environment we require libvirt use then QEMU by itself is less usable. We do have machine types in QEMU to expose stable machine to a guest. CPU models should be part of it. -- Gleb. -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Sun, Mar 11, 2012 at 09:12:58AM -0500, Anthony Liguori wrote: > On 03/11/2012 08:27 AM, Gleb Natapov wrote: > >On Sat, Mar 10, 2012 at 12:24:47PM -0600, Anthony Liguori wrote: > >>Let's step back here. > >> > >>Why are you writing these patches? It's probably not because you > >>have a desire to say -cpu Westmere when you run QEMU on your laptop. > >>I'd wager to say that no human has ever done that or that if they > >>had, they did so by accident because they read documentation and > >>thought they had to. > >> > >I'd be glad if QEMU will chose -cpu Westmere for me if it detects > >Westmere host CPU as a default. > > This is -cpu best that Alex proposed FWIW. > I didn't look at exact implementation but I doubt it does exactly what we need because currently we do not have infrastructure for that. If qemu is upgraded with support for new cpuid bits and -cpu best will pass them to a guest on next boot then this is not the same. -cpu Westmere can mean different thing for different machine types with proper infrastructure in place. > >>Humans probably do one of two things: 1) no cpu option or 2) -cpu host. > >> > >And both are not optimal. Actually both are bad. First one because > >default cpu is very conservative and the second because there is no > >guaranty that guest will continue to work after qemu or kernel upgrade. > > > >Let me elaborate about the later. Suppose host CPU has kill_guest > >feature and at the time a guest was installed it was not implemented by > >kvm. Since it was not implemented by kvm it was not present in vcpu > >during installation and the guest didn't install "workaround kill_guest" > >module. Now unsuspecting user upgrades the kernel and tries to restart > >the guest and fails. He writes angry letter to qemu-devel and is asked to > >reinstall his guest and move along. > > -cpu best wouldn't solve this. You need a read/write configuration > file where QEMU probes the available CPU and records it to be used > for the lifetime of the VM. That what I thought too, but this shouldn't be the case (Avi's idea). We need two things: 1) CPU model config should be per machine type. 2) QEMU should refuse to start if it cannot create cpu exactly as specified by model config. With two conditions above if user creates VM with qemu 1.0 and cpu model Westmere which has no kill_guest feature he will still be able to run it in QEMU 1.1 (where kill_guest is added to Westmere model) and new kvm that support kill_guest by providing -M pc-1.0 flag (old definition of Westmere will be used). If user will try to create VM with QEMU 1.1 on a kernel that does not support kill_guest QEMU will refuse to start. > > >>So then why are you introducing -cpu Westmere? Because ovirt-engine > >>has a concept of datacenters and the entire datacenter has to use a > >>compatible CPU model to allow migration compatibility. Today, the > >>interface that ovirt-engine exposes is based on CPU codenames. > >>Presumably ovirt-engine wants to add a Westmere CPU group and as > >>such have levied a requirement down the stack to QEMU. > >> > >First of all this is not about live migration only. Guest visible vcpu > >should not change after guest reboot (or hibernate/resume) too. And > >second this concept exists with only your laptop and single guest on it > >too. There are three inputs into a "CPU model module": 1) host cpu, 2) > >qemu capabilities, 3) kvm capabilities. With datacenters scenario all > >three can change, with your laptop only last two can change (first one > >can change too when you'll get new laptop) , but the net result is that > >guest visible cpuid can change and it shouldn't. This is the goal of > >introducing -cpu Westmere, to prevent it from happening. > > This discussion isn't about whether QEMU should have a Westmere > processor definition. In fact, I think I already applied that > patch. > > It's a discussion about how we handle this up and down the stack. > > The question is who should define and manage CPU compatibility. > Right now QEMU does to a certain degree, libvirt discards this and > does it's own thing, and VDSM/ovirt-engine assume that we're > providing something and has built a UI around it. If we want QEMU to be usable without management layer then QEMU should provide stable CPU models. Stable in a sense that qemu, kernel or CPU upgrade does not change what guest sees. If libvirt wants to override QEMU we should have a way to allow that, but than compatibility becomes libvirt problem. Figuring out what minimal CPU model that can be used across a cluster of different machines should be ovirt task. > > What I'm proposing we consider: have VDSM manage CPU definitions in > order to provide a specific user experience in ovirt-engine. > > We would continue to have Westmere/etc in QEMU exposed as part of > the user configuration. But I don't think it makes a lot of sense > to have to modify QEMU any time a new CPU comes out. > If new cpu does not provide any new instruction se
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/11/2012 07:41 AM, Gleb Natapov wrote: On Sat, Mar 10, 2012 at 12:58:43PM -0300, Eduardo Habkost wrote: On Sat, Mar 10, 2012 at 12:42:46PM +, Daniel P. Berrange wrote: I could have sworn we had this discussion a year ago or so, and had decided that the default CPU models would be in something like /usr/share/qemu/cpu-x86_64.conf and loaded regardless of the -nodefconfig setting. /etc/qemu/target-x86_64.conf would be solely for end user configuration changes, not for QEMU builtin defaults. But looking at the code in QEMU, it doesn't seem we ever implemented this ? Arrrgggh. It seems this was implemented as a patch in RHEL-6 qemu RPMs but, contrary to our normal RHEL development practice, it was not based on a cherry-pick of an upstream patch :-( For sake of reference, I'm attaching the two patches from the RHEL6 source RPM that do what I'm describing NB, I'm not neccessarily advocating these patches for upstream. I still maintain that libvirt should write out a config file containing the exact CPU model description it desires and specify that with -readconfig. The end result would be identical from QEMU's POV and it would avoid playing games with QEMU's config loading code. I agree that libvirt should just write the config somewhere. The problem here is to define: 1) what information should be mandatory on that config data; 2) who should be responsible to test and maintain sane defaults (and where should they be maintained). The current cpudef definitions are simply too low-level to require it to be written from scratch. Lots of testing have to be done to make sure we have working combinations of CPUID bits defined, so they can be used as defaults or templates. Not facilitating reuse of those tested defauls/templates by libvirt is duplication of efforts. Really, if we expect libvirt to define all the CPU bits from scratch on a config file, we could as well just expect libvirt to open /dev/kvm itself and call the all CPUID setup ioctl()s itself. That's how low-level some of the cpudef bits are. s/some/all If libvirt assumes anything about what kvm actually supports it is working only by sheer luck. Well the simple answer for libvirt is don't use -nodefconfig and then it can reuse the CPU definitions (including any that the user adds). Really, what's the point of having a layer of management if we're saying that doing policy management is too complicated for that layer? What does that layer exist to provide then? (Also, there are additional low-level bits that really have to be maintained somewhere, just to have sane defaults. Currently many CPUID leafs are exposed to the guest without letting the user control them, and worse: without keeping stability of guest-visible bits when upgrading Qemu or the host kernel. And that's what machine-types are for: to have sane defaults to be used as base.) Let me give you a practical example: I had a bug report about improper CPU topology information[1]. After investigating it, I have found out that the "level" cpudef field is too low; CPU core topology information is provided on CPUID leaf 4, and most of the Intel CPU models on Qemu have level=2 today (I don't know why). So, Qemu is responsible for exposing CPU topology information set using '-smp' to the guest OS, but libvirt would have to be responsible for choosing a proper "level" value that makes that information visible to the guest. We can _allow_ libvirt to fiddle with these low-level bits, of course, but requiring every management layer to build this low-level information from scratch is just a recipe to waste developer time. And QEMU become even less usable from a command line. One more point to kvm-tool I guess. I'm not sure what your point is. We're talking about an option that humans don't use. How is this a discussion about QEMU usability? Regards, Anthony Liguori -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/11/2012 08:27 AM, Gleb Natapov wrote: On Sat, Mar 10, 2012 at 12:24:47PM -0600, Anthony Liguori wrote: Let's step back here. Why are you writing these patches? It's probably not because you have a desire to say -cpu Westmere when you run QEMU on your laptop. I'd wager to say that no human has ever done that or that if they had, they did so by accident because they read documentation and thought they had to. I'd be glad if QEMU will chose -cpu Westmere for me if it detects Westmere host CPU as a default. This is -cpu best that Alex proposed FWIW. Humans probably do one of two things: 1) no cpu option or 2) -cpu host. And both are not optimal. Actually both are bad. First one because default cpu is very conservative and the second because there is no guaranty that guest will continue to work after qemu or kernel upgrade. Let me elaborate about the later. Suppose host CPU has kill_guest feature and at the time a guest was installed it was not implemented by kvm. Since it was not implemented by kvm it was not present in vcpu during installation and the guest didn't install "workaround kill_guest" module. Now unsuspecting user upgrades the kernel and tries to restart the guest and fails. He writes angry letter to qemu-devel and is asked to reinstall his guest and move along. -cpu best wouldn't solve this. You need a read/write configuration file where QEMU probes the available CPU and records it to be used for the lifetime of the VM. So then why are you introducing -cpu Westmere? Because ovirt-engine has a concept of datacenters and the entire datacenter has to use a compatible CPU model to allow migration compatibility. Today, the interface that ovirt-engine exposes is based on CPU codenames. Presumably ovirt-engine wants to add a Westmere CPU group and as such have levied a requirement down the stack to QEMU. First of all this is not about live migration only. Guest visible vcpu should not change after guest reboot (or hibernate/resume) too. And second this concept exists with only your laptop and single guest on it too. There are three inputs into a "CPU model module": 1) host cpu, 2) qemu capabilities, 3) kvm capabilities. With datacenters scenario all three can change, with your laptop only last two can change (first one can change too when you'll get new laptop) , but the net result is that guest visible cpuid can change and it shouldn't. This is the goal of introducing -cpu Westmere, to prevent it from happening. This discussion isn't about whether QEMU should have a Westmere processor definition. In fact, I think I already applied that patch. It's a discussion about how we handle this up and down the stack. The question is who should define and manage CPU compatibility. Right now QEMU does to a certain degree, libvirt discards this and does it's own thing, and VDSM/ovirt-engine assume that we're providing something and has built a UI around it. What I'm proposing we consider: have VDSM manage CPU definitions in order to provide a specific user experience in ovirt-engine. We would continue to have Westmere/etc in QEMU exposed as part of the user configuration. But I don't think it makes a lot of sense to have to modify QEMU any time a new CPU comes out. Regards, Anthony Liguori -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Sat, Mar 10, 2012 at 12:24:47PM -0600, Anthony Liguori wrote: > Let's step back here. > > Why are you writing these patches? It's probably not because you > have a desire to say -cpu Westmere when you run QEMU on your laptop. > I'd wager to say that no human has ever done that or that if they > had, they did so by accident because they read documentation and > thought they had to. > I'd be glad if QEMU will chose -cpu Westmere for me if it detects Westmere host CPU as a default. > Humans probably do one of two things: 1) no cpu option or 2) -cpu host. > And both are not optimal. Actually both are bad. First one because default cpu is very conservative and the second because there is no guaranty that guest will continue to work after qemu or kernel upgrade. Let me elaborate about the later. Suppose host CPU has kill_guest feature and at the time a guest was installed it was not implemented by kvm. Since it was not implemented by kvm it was not present in vcpu during installation and the guest didn't install "workaround kill_guest" module. Now unsuspecting user upgrades the kernel and tries to restart the guest and fails. He writes angry letter to qemu-devel and is asked to reinstall his guest and move along. > So then why are you introducing -cpu Westmere? Because ovirt-engine > has a concept of datacenters and the entire datacenter has to use a > compatible CPU model to allow migration compatibility. Today, the > interface that ovirt-engine exposes is based on CPU codenames. > Presumably ovirt-engine wants to add a Westmere CPU group and as > such have levied a requirement down the stack to QEMU. > First of all this is not about live migration only. Guest visible vcpu should not change after guest reboot (or hibernate/resume) too. And second this concept exists with only your laptop and single guest on it too. There are three inputs into a "CPU model module": 1) host cpu, 2) qemu capabilities, 3) kvm capabilities. With datacenters scenario all three can change, with your laptop only last two can change (first one can change too when you'll get new laptop) , but the net result is that guest visible cpuid can change and it shouldn't. This is the goal of introducing -cpu Westmere, to prevent it from happening. > But there's no intrinsic reason why it uses CPU model names. VMware > doesn't do this. It has a concept of compatibility groups[1]. > As Andrew noted, not any more. There is no intrinsic reason, but people are more familiar with Intel terminology than random hypervisor terminology. > oVirt could just as well define compatibility groups like GroupA, > GroupB, GroupC, etc. and then the -cpu option we would be discussing > would be -cpu GroupA. It could, but I can't see why this is less confusing. > > This is why it's a configuration option and not builtin to QEMU. > It's a user interface as as such, should be defined at a higher > level. This is not the only configuration that is builtin in QEMU. As it stands now QEMU does not even allow configuring cpuid enough to define those compatibility groups outside of QEMU. And after the work is done to allow enough configurability there is no much left to provide compatibility groups in QEMU itself. > > Perhaps it really should be VDSM that is providing the model info to > libvirt? Then they can add whatever groups then want whenever they > want as long as we have the appropriate feature bits. > > P.S. I spent 30 minutes the other day helping a user who was > attempting to figure out whether his processor was a Conroe, Penryn, > etc. Making this determination is fairly difficult and it makes me > wonder whether having CPU code names is even the best interface for > oVirt.. > > [1] > http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1991 > > Regards, > > Anthony Liguori > > > > >(Also, there are additional low-level bits that really have to be > >maintained somewhere, just to have sane defaults. Currently many CPUID > >leafs are exposed to the guest without letting the user control them, > >and worse: without keeping stability of guest-visible bits when > >upgrading Qemu or the host kernel. And that's what machine-types are > >for: to have sane defaults to be used as base.) > > > >Let me give you a practical example: I had a bug report about improper > >CPU topology information[1]. After investigating it, I have found out > >that the "level" cpudef field is too low; CPU core topology information > >is provided on CPUID leaf 4, and most of the Intel CPU models on Qemu > >have level=2 today (I don't know why). So, Qemu is responsible for > >exposing CPU topology information set using '-smp' to the guest OS, but > >libvirt would have to be responsible for choosing a proper "level" value > >that makes that information visible to the guest. We can _allow_ libvirt > >to fiddle with these low-level bits, of course, but requiring every > >management layer to build this low-level information from s
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Sat, Mar 10, 2012 at 12:58:43PM -0300, Eduardo Habkost wrote: > On Sat, Mar 10, 2012 at 12:42:46PM +, Daniel P. Berrange wrote: > > > > > > I could have sworn we had this discussion a year ago or so, and had > > > decided > > > that the default CPU models would be in something like > > > /usr/share/qemu/cpu-x86_64.conf > > > and loaded regardless of the -nodefconfig setting. > > > /etc/qemu/target-x86_64.conf > > > would be solely for end user configuration changes, not for QEMU builtin > > > defaults. > > > > > > But looking at the code in QEMU, it doesn't seem we ever implemented this > > > ? > > > > Arrrgggh. It seems this was implemented as a patch in RHEL-6 qemu RPMs but, > > contrary to our normal RHEL development practice, it was not based on > > a cherry-pick of an upstream patch :-( > > > > For sake of reference, I'm attaching the two patches from the RHEL6 source > > RPM that do what I'm describing > > > > NB, I'm not neccessarily advocating these patches for upstream. I still > > maintain that libvirt should write out a config file containing the > > exact CPU model description it desires and specify that with -readconfig. > > The end result would be identical from QEMU's POV and it would avoid > > playing games with QEMU's config loading code. > > I agree that libvirt should just write the config somewhere. The problem > here is to define: 1) what information should be mandatory on that > config data; 2) who should be responsible to test and maintain sane > defaults (and where should they be maintained). > > The current cpudef definitions are simply too low-level to require it to > be written from scratch. Lots of testing have to be done to make sure we > have working combinations of CPUID bits defined, so they can be used as > defaults or templates. Not facilitating reuse of those tested > defauls/templates by libvirt is duplication of efforts. > > Really, if we expect libvirt to define all the CPU bits from scratch on > a config file, we could as well just expect libvirt to open /dev/kvm > itself and call the all CPUID setup ioctl()s itself. That's how > low-level some of the cpudef bits are. > s/some/all If libvirt assumes anything about what kvm actually supports it is working only by sheer luck. > (Also, there are additional low-level bits that really have to be > maintained somewhere, just to have sane defaults. Currently many CPUID > leafs are exposed to the guest without letting the user control them, > and worse: without keeping stability of guest-visible bits when > upgrading Qemu or the host kernel. And that's what machine-types are > for: to have sane defaults to be used as base.) > > Let me give you a practical example: I had a bug report about improper > CPU topology information[1]. After investigating it, I have found out > that the "level" cpudef field is too low; CPU core topology information > is provided on CPUID leaf 4, and most of the Intel CPU models on Qemu > have level=2 today (I don't know why). So, Qemu is responsible for > exposing CPU topology information set using '-smp' to the guest OS, but > libvirt would have to be responsible for choosing a proper "level" value > that makes that information visible to the guest. We can _allow_ libvirt > to fiddle with these low-level bits, of course, but requiring every > management layer to build this low-level information from scratch is > just a recipe to waste developer time. And QEMU become even less usable from a command line. One more point to kvm-tool I guess. > > (And I really hope that there's no plan to require all those low-level > bits to appear as-is on the libvirt XML definitions. Because that would > require users to read the Intel 64 and IA-32 Architectures Software > Developer's Manual, or the AMD64 Architecture Programmer's Manual and > BIOS and Kernel Developer's Guides, just to understand why something is > not working on his Virtual Machine.) > > [1] https://bugzilla.redhat.com/show_bug.cgi?id=689665 > > -- > Eduardo -- Gleb. -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
- Original Message - > From: "Anthony Liguori" > To: "Daniel P. Berrange" , libvir-list@redhat.com, > qemu-de...@nongnu.org, "Gleb Natapov" > , "Jiri Denemark" , "Avi Kivity" > , a...@ovirt.org > Sent: Saturday, March 10, 2012 1:24:47 PM > Subject: Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with > libvirt > > On 03/10/2012 09:58 AM, Eduardo Habkost wrote: > > On Sat, Mar 10, 2012 at 12:42:46PM +, Daniel P. Berrange wrote: > >>> > >>> I could have sworn we had this discussion a year ago or so, and > >>> had decided > >>> that the default CPU models would be in something like > >>> /usr/share/qemu/cpu-x86_64.conf > >>> and loaded regardless of the -nodefconfig setting. > >>> /etc/qemu/target-x86_64.conf > >>> would be solely for end user configuration changes, not for QEMU > >>> builtin > >>> defaults. > >>> > >>> But looking at the code in QEMU, it doesn't seem we ever > >>> implemented this ? > >> > >> Arrrgggh. It seems this was implemented as a patch in RHEL-6 qemu > >> RPMs but, > >> contrary to our normal RHEL development practice, it was not based > >> on > >> a cherry-pick of an upstream patch :-( > >> > >> For sake of reference, I'm attaching the two patches from the > >> RHEL6 source > >> RPM that do what I'm describing > >> > >> NB, I'm not neccessarily advocating these patches for upstream. I > >> still > >> maintain that libvirt should write out a config file containing > >> the > >> exact CPU model description it desires and specify that with > >> -readconfig. > >> The end result would be identical from QEMU's POV and it would > >> avoid > >> playing games with QEMU's config loading code. > > > > I agree that libvirt should just write the config somewhere. The > > problem > > here is to define: 1) what information should be mandatory on that > > config data; 2) who should be responsible to test and maintain sane > > defaults (and where should they be maintained). > > > > The current cpudef definitions are simply too low-level to require > > it to > > be written from scratch. Lots of testing have to be done to make > > sure we > > have working combinations of CPUID bits defined, so they can be > > used as > > defaults or templates. Not facilitating reuse of those tested > > defauls/templates by libvirt is duplication of efforts. > > > > Really, if we expect libvirt to define all the CPU bits from > > scratch on > > a config file, we could as well just expect libvirt to open > > /dev/kvm > > itself and call the all CPUID setup ioctl()s itself. That's how > > low-level some of the cpudef bits are. > > Let's step back here. > > Why are you writing these patches? It's probably not because you > have a desire > to say -cpu Westmere when you run QEMU on your laptop. I'd wager to > say that no > human has ever done that or that if they had, they did so by accident > because > they read documentation and thought they had to. > > Humans probably do one of two things: 1) no cpu option or 2) -cpu > host. > > So then why are you introducing -cpu Westmere? Because ovirt-engine > has a > concept of datacenters and the entire datacenter has to use a > compatible CPU > model to allow migration compatibility. Today, the interface that > ovirt-engine > exposes is based on CPU codenames. Presumably ovirt-engine wants to > add a > Westmere CPU group and as such have levied a requirement down the > stack to QEMU. > > But there's no intrinsic reason why it uses CPU model names. VMware > doesn't do > this. It has a concept of compatibility groups[1]. s/has/had That was back in the 3.5 days and it was hit and miss, it relied on a user putting the same kind of machines in the resource groups and often caused issues. Now they've moved up to a model very similar to what we're using: http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1003212 > > oVirt could just as well define compatibility groups like GroupA, > GroupB, > GroupC, etc. and then the -cpu option we would be discussing would be > -cpu GroupA. > > This is why it's a configuration option and not builtin to QEMU. > It's a user > interface as as such, should be defined at a higher level. > > Perhaps it really should
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Sat, Mar 10, 2012 at 12:24 PM, Anthony Liguori wrote: > On 03/10/2012 09:58 AM, Eduardo Habkost wrote: >> >> On Sat, Mar 10, 2012 at 12:42:46PM +, Daniel P. Berrange wrote: I could have sworn we had this discussion a year ago or so, and had decided that the default CPU models would be in something like /usr/share/qemu/cpu-x86_64.conf and loaded regardless of the -nodefconfig setting. /etc/qemu/target-x86_64.conf would be solely for end user configuration changes, not for QEMU builtin defaults. But looking at the code in QEMU, it doesn't seem we ever implemented this ? >>> >>> >>> Arrrgggh. It seems this was implemented as a patch in RHEL-6 qemu RPMs >>> but, >>> contrary to our normal RHEL development practice, it was not based on >>> a cherry-pick of an upstream patch :-( >>> >>> For sake of reference, I'm attaching the two patches from the RHEL6 >>> source >>> RPM that do what I'm describing >>> >>> NB, I'm not neccessarily advocating these patches for upstream. I still >>> maintain that libvirt should write out a config file containing the >>> exact CPU model description it desires and specify that with -readconfig. >>> The end result would be identical from QEMU's POV and it would avoid >>> playing games with QEMU's config loading code. >> >> >> I agree that libvirt should just write the config somewhere. The problem >> here is to define: 1) what information should be mandatory on that >> config data; 2) who should be responsible to test and maintain sane >> defaults (and where should they be maintained). >> >> The current cpudef definitions are simply too low-level to require it to >> be written from scratch. Lots of testing have to be done to make sure we >> have working combinations of CPUID bits defined, so they can be used as >> defaults or templates. Not facilitating reuse of those tested >> defauls/templates by libvirt is duplication of efforts. >> >> Really, if we expect libvirt to define all the CPU bits from scratch on >> a config file, we could as well just expect libvirt to open /dev/kvm >> itself and call the all CPUID setup ioctl()s itself. That's how >> low-level some of the cpudef bits are. > > > Let's step back here. > > Why are you writing these patches? It's probably not because you have a > desire to say -cpu Westmere when you run QEMU on your laptop. I'd wager to > say that no human has ever done that or that if they had, they did so by > accident because they read documentation and thought they had to. > > Humans probably do one of two things: 1) no cpu option or 2) -cpu host. > > So then why are you introducing -cpu Westmere? Because ovirt-engine has a > concept of datacenters and the entire datacenter has to use a compatible CPU > model to allow migration compatibility. Today, the interface that > ovirt-engine exposes is based on CPU codenames. Presumably ovirt-engine > wants to add a Westmere CPU group and as such have levied a requirement down > the stack to QEMU. > > But there's no intrinsic reason why it uses CPU model names. VMware doesn't > do this. It has a concept of compatibility groups[1]. > > oVirt could just as well define compatibility groups like GroupA, GroupB, > GroupC, etc. and then the -cpu option we would be discussing would be -cpu > GroupA. > > This is why it's a configuration option and not builtin to QEMU. It's a > user interface as as such, should be defined at a higher level. > > Perhaps it really should be VDSM that is providing the model info to > libvirt? Then they can add whatever groups then want whenever they want as > long as we have the appropriate feature bits. > > P.S. I spent 30 minutes the other day helping a user who was attempting to > figure out whether his processor was a Conroe, Penryn, etc. Making this > determination is fairly difficult and it makes me wonder whether having CPU > code names is even the best interface for oVirt.. > > [1] > http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1991 > > Regards, > > Anthony Liguori FWIW, as a user this would be a good improvement. As it stands right now when a cluster of machines is established as being redundant migratable machines for each other I must do the following for each machine: virsh -c qemu://machine/system capabilities | xpath /capabilities/host/cpu > machine-cpu.xml Once I have that data I combine them together and use virsh cpu-baseline, which is a handy addition from the past of doing it manually, but still not optimal. This gives me a model which is mostly meaningless and uninteresting to me, but I know all the guests must use Penryn for example. If ovirt and by extension libvirt let me know that guest X is running on CPU-A, I know I could migrate it to any other machine supporting CPU-A or CPU-B (assuming B is a super set of A). -- Doug Goldstein -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 03/10/2012 09:58 AM, Eduardo Habkost wrote: On Sat, Mar 10, 2012 at 12:42:46PM +, Daniel P. Berrange wrote: I could have sworn we had this discussion a year ago or so, and had decided that the default CPU models would be in something like /usr/share/qemu/cpu-x86_64.conf and loaded regardless of the -nodefconfig setting. /etc/qemu/target-x86_64.conf would be solely for end user configuration changes, not for QEMU builtin defaults. But looking at the code in QEMU, it doesn't seem we ever implemented this ? Arrrgggh. It seems this was implemented as a patch in RHEL-6 qemu RPMs but, contrary to our normal RHEL development practice, it was not based on a cherry-pick of an upstream patch :-( For sake of reference, I'm attaching the two patches from the RHEL6 source RPM that do what I'm describing NB, I'm not neccessarily advocating these patches for upstream. I still maintain that libvirt should write out a config file containing the exact CPU model description it desires and specify that with -readconfig. The end result would be identical from QEMU's POV and it would avoid playing games with QEMU's config loading code. I agree that libvirt should just write the config somewhere. The problem here is to define: 1) what information should be mandatory on that config data; 2) who should be responsible to test and maintain sane defaults (and where should they be maintained). The current cpudef definitions are simply too low-level to require it to be written from scratch. Lots of testing have to be done to make sure we have working combinations of CPUID bits defined, so they can be used as defaults or templates. Not facilitating reuse of those tested defauls/templates by libvirt is duplication of efforts. Really, if we expect libvirt to define all the CPU bits from scratch on a config file, we could as well just expect libvirt to open /dev/kvm itself and call the all CPUID setup ioctl()s itself. That's how low-level some of the cpudef bits are. Let's step back here. Why are you writing these patches? It's probably not because you have a desire to say -cpu Westmere when you run QEMU on your laptop. I'd wager to say that no human has ever done that or that if they had, they did so by accident because they read documentation and thought they had to. Humans probably do one of two things: 1) no cpu option or 2) -cpu host. So then why are you introducing -cpu Westmere? Because ovirt-engine has a concept of datacenters and the entire datacenter has to use a compatible CPU model to allow migration compatibility. Today, the interface that ovirt-engine exposes is based on CPU codenames. Presumably ovirt-engine wants to add a Westmere CPU group and as such have levied a requirement down the stack to QEMU. But there's no intrinsic reason why it uses CPU model names. VMware doesn't do this. It has a concept of compatibility groups[1]. oVirt could just as well define compatibility groups like GroupA, GroupB, GroupC, etc. and then the -cpu option we would be discussing would be -cpu GroupA. This is why it's a configuration option and not builtin to QEMU. It's a user interface as as such, should be defined at a higher level. Perhaps it really should be VDSM that is providing the model info to libvirt? Then they can add whatever groups then want whenever they want as long as we have the appropriate feature bits. P.S. I spent 30 minutes the other day helping a user who was attempting to figure out whether his processor was a Conroe, Penryn, etc. Making this determination is fairly difficult and it makes me wonder whether having CPU code names is even the best interface for oVirt.. [1] http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1991 Regards, Anthony Liguori (Also, there are additional low-level bits that really have to be maintained somewhere, just to have sane defaults. Currently many CPUID leafs are exposed to the guest without letting the user control them, and worse: without keeping stability of guest-visible bits when upgrading Qemu or the host kernel. And that's what machine-types are for: to have sane defaults to be used as base.) Let me give you a practical example: I had a bug report about improper CPU topology information[1]. After investigating it, I have found out that the "level" cpudef field is too low; CPU core topology information is provided on CPUID leaf 4, and most of the Intel CPU models on Qemu have level=2 today (I don't know why). So, Qemu is responsible for exposing CPU topology information set using '-smp' to the guest OS, but libvirt would have to be responsible for choosing a proper "level" value that makes that information visible to the guest. We can _allow_ libvirt to fiddle with these low-level bits, of course, but requiring every management layer to build this low-level information from scratch is just a recipe to waste developer time. (And I really hope that there's no plan to requi
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Sat, Mar 10, 2012 at 12:42:46PM +, Daniel P. Berrange wrote: > > > > I could have sworn we had this discussion a year ago or so, and had decided > > that the default CPU models would be in something like > > /usr/share/qemu/cpu-x86_64.conf > > and loaded regardless of the -nodefconfig setting. > > /etc/qemu/target-x86_64.conf > > would be solely for end user configuration changes, not for QEMU builtin > > defaults. > > > > But looking at the code in QEMU, it doesn't seem we ever implemented this ? > > Arrrgggh. It seems this was implemented as a patch in RHEL-6 qemu RPMs but, > contrary to our normal RHEL development practice, it was not based on > a cherry-pick of an upstream patch :-( > > For sake of reference, I'm attaching the two patches from the RHEL6 source > RPM that do what I'm describing > > NB, I'm not neccessarily advocating these patches for upstream. I still > maintain that libvirt should write out a config file containing the > exact CPU model description it desires and specify that with -readconfig. > The end result would be identical from QEMU's POV and it would avoid > playing games with QEMU's config loading code. I agree that libvirt should just write the config somewhere. The problem here is to define: 1) what information should be mandatory on that config data; 2) who should be responsible to test and maintain sane defaults (and where should they be maintained). The current cpudef definitions are simply too low-level to require it to be written from scratch. Lots of testing have to be done to make sure we have working combinations of CPUID bits defined, so they can be used as defaults or templates. Not facilitating reuse of those tested defauls/templates by libvirt is duplication of efforts. Really, if we expect libvirt to define all the CPU bits from scratch on a config file, we could as well just expect libvirt to open /dev/kvm itself and call the all CPUID setup ioctl()s itself. That's how low-level some of the cpudef bits are. (Also, there are additional low-level bits that really have to be maintained somewhere, just to have sane defaults. Currently many CPUID leafs are exposed to the guest without letting the user control them, and worse: without keeping stability of guest-visible bits when upgrading Qemu or the host kernel. And that's what machine-types are for: to have sane defaults to be used as base.) Let me give you a practical example: I had a bug report about improper CPU topology information[1]. After investigating it, I have found out that the "level" cpudef field is too low; CPU core topology information is provided on CPUID leaf 4, and most of the Intel CPU models on Qemu have level=2 today (I don't know why). So, Qemu is responsible for exposing CPU topology information set using '-smp' to the guest OS, but libvirt would have to be responsible for choosing a proper "level" value that makes that information visible to the guest. We can _allow_ libvirt to fiddle with these low-level bits, of course, but requiring every management layer to build this low-level information from scratch is just a recipe to waste developer time. (And I really hope that there's no plan to require all those low-level bits to appear as-is on the libvirt XML definitions. Because that would require users to read the Intel 64 and IA-32 Architectures Software Developer's Manual, or the AMD64 Architecture Programmer's Manual and BIOS and Kernel Developer's Guides, just to understand why something is not working on his Virtual Machine.) [1] https://bugzilla.redhat.com/show_bug.cgi?id=689665 -- Eduardo -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Fri, Mar 09, 2012 at 03:15:26PM -0600, Anthony Liguori wrote: > On 03/09/2012 03:04 PM, Daniel P. Berrange wrote: > >On Fri, Mar 09, 2012 at 05:56:52PM -0300, Eduardo Habkost wrote: > >>Resurrecting an old thread: > >> > >>I didn't see any clear conclusion in this thread (this is why I am > >>resurrecting it), except that many were arguing that libvirt should > >>simply copy and/or generate the CPU model definitions from Qemu. I > >>really don't think it's reasonable to expect that. > >> > >>On Thu, Dec 15, 2011 at 03:54:15PM +0100, Jiri Denemark wrote: > >>>Hi, > >>> > >>>Recently I realized that all modern CPU models defined in > >>>/etc/qemu/target-x86_64.conf are useless when qemu is used through libvirt. > >>>That's because we start qemu with -nodefconfig which results in qemu > >>>ignoring > >>>that file with CPU model definitions. We have a very good reason for using > >>>-nodefconfig because we need to control the ABI presented to a guest OS > >>>and we > >>>don't want any configuration file that can contain lots of things including > >>>device definitions to be read by qemu. However, we would really like the > >>>new > >>>CPU models to be understood by qemu even if used through libvirt. What > >>>would > >>>be the best way to solve this? > >>> > >>>I suspect this could have been already discussed in the past but obviously > >>>a > >>>workable solution was either not found or just not implemented. > >> > >>So, our problem today is basically: > >> > >>A) libvirt uses -nodefconfig; > >>B) -nodefconfig makes Qemu not load the config file containing the CPU > >>model definitions; and > >>C) libvirt expects the full CPU model list from Qemu to be available. > > > >I could have sworn we had this discussion a year ago or so, and had decided > >that the default CPU models would be in something like > >/usr/share/qemu/cpu-x86_64.conf > >and loaded regardless of the -nodefconfig setting. > >/etc/qemu/target-x86_64.conf > >would be solely for end user configuration changes, not for QEMU builtin > >defaults. > > > >But looking at the code in QEMU, it doesn't seem we ever implemented this ? > > I don't remember that discussion and really don't think I agree with the > conclusion. > > If libvirt wants to define CPU models on their own, they can. If > libvirt wants to use the user's definitions, don't use -nodefconfig. > > CPU models aren't a QEMU concept. The reason it's in the > configuration file is to allow a user to add their own as they see > fit. There is no right model names. It's strictly a policy. Honestly, I don't think every single detail of CPU definitions should be considered user-provided configuration, the cpudefs are a low-level definitions of known-to-work combinations of CPUID bits, not a proper way for a user (or even a upper layer such as libvirt) to configure a CPU from scratch. At least a set of sane defaults to be used as base should be part of what defines a "machine type". If we don't do that, we will be unable to fix bugs on those CPU definitions without having to tell users to edit their config files, and libvirt users won't be able to use any new CPU feature until support for them is implemented on libvirt. And we would confuse two sets of users: 1) the ones that are using old cpudefs but don't understand why new features aren't available even on newer machine-types (and will have to read the Intel or AMD developer manuals to understand how to enable the feature); 2) the ones that get their config files upgraded automatically and don't understand why they are getting a different virtual machine after the upgrade, even when using an older machine-type. -- Eduardo -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 12/15/2011 05:30 PM, Jiri Denemark wrote: On Thu, Dec 15, 2011 at 08:58:55 -0600, Anthony Liguori wrote: Pass '-readconfig /etc/qemu/target-x86_64.conf' to pick up those models and if you are absolutely insistent on not giving the user any ability to change things on their own, cp the file from qemu.git into libvirt.git and install it in a safe place. Ah, this looks like a good idea (and we could even generate that file dynamically if we add support for family/stepping/... and other things that we do not model now). However, separating these definitions from qemu may result in incompatibilities with older qemu versions. I guess mainly because our configuration file would mention a CPU feature that an installed qemu version doesn't understand. Currently, qemu seems to just ignore such feature (although it prints an error) and continues happily without it. Is there any way for us to ask qemu what CPU features it knows about so that we could avoid using a CPU models which include features qemu doesn't understand? Libvirt should use the 'enforce' option and there is also a 'check' one too: > qemu-kvm -cpu Conroe,+avx,enforce warning: host cpuid _0001 lacks requested flag 'avx' [0x1000] Unable to find x86 CPU definition Qemu supports backward compatibility of the command line and if libvirt stores additional cpuid related definitions it should still work on other qemu releases. btw: I do prompt the usage of the 'formal' cpu models as much as it can. If a user likes to toggle various options it should do it on top of our models. Regards, Dor Jirka -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Thu, Dec 15, 2011 at 03:42:44PM +, Daniel P. Berrange wrote: > On Thu, Dec 15, 2011 at 03:54:15PM +0100, Jiri Denemark wrote: > > Hi, > > > > Recently I realized that all modern CPU models defined in > > /etc/qemu/target-x86_64.conf are useless when qemu is used through libvirt. > > That's because we start qemu with -nodefconfig which results in qemu > > ignoring > > that file with CPU model definitions. We have a very good reason for using > > -nodefconfig because we need to control the ABI presented to a guest OS and > > we > > don't want any configuration file that can contain lots of things including > > device definitions to be read by qemu. However, we would really like the new > > CPU models to be understood by qemu even if used through libvirt. What would > > be the best way to solve this? > > Ideally libvirt would just write out a config file with the CPU > that was configured in libvirt and pass -readconfig > /var/lib/libvirt/qemu/guestcpu.conf > That way libvirt can configure CPU models without regard for > what the particular QEMU version might have in its config. > And how libvirt would know that particular QEMU/kvm version can create this CPU. Managing cpuid shouldn't be libvirt busyness. -- Gleb. -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On Thu, Dec 15, 2011 at 08:58:55 -0600, Anthony Liguori wrote: > Pass '-readconfig /etc/qemu/target-x86_64.conf' to pick up those models and > if > you are absolutely insistent on not giving the user any ability to change > things > on their own, cp the file from qemu.git into libvirt.git and install it in a > safe place. Ah, this looks like a good idea (and we could even generate that file dynamically if we add support for family/stepping/... and other things that we do not model now). However, separating these definitions from qemu may result in incompatibilities with older qemu versions. I guess mainly because our configuration file would mention a CPU feature that an installed qemu version doesn't understand. Currently, qemu seems to just ignore such feature (although it prints an error) and continues happily without it. Is there any way for us to ask qemu what CPU features it knows about so that we could avoid using a CPU models which include features qemu doesn't understand? Jirka -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [Qemu-devel] Modern CPU models cannot be used with libvirt
On 12/15/2011 08:54 AM, Jiri Denemark wrote: Hi, Recently I realized that all modern CPU models defined in /etc/qemu/target-x86_64.conf are useless when qemu is used through libvirt. That's because we start qemu with -nodefconfig which results in qemu ignoring that file with CPU model definitions. We have a very good reason for using -nodefconfig because we need to control the ABI presented to a guest OS and we don't want any configuration file that can contain lots of things including device definitions to be read by qemu. However, we would really like the new CPU models to be understood by qemu even if used through libvirt. What would be the best way to solve this? Pass '-readconfig /etc/qemu/target-x86_64.conf' to pick up those models and if you are absolutely insistent on not giving the user any ability to change things on their own, cp the file from qemu.git into libvirt.git and install it in a safe place. Regards, Anthony Liguori I suspect this could have been already discussed in the past but obviously a workable solution was either not found or just not implemented. Jirka -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
