On Tue, Oct 10, 2017 at 8:25 AM, Eduardo Habkost <ehabk...@redhat.com> wrote: > On Mon, Oct 09, 2017 at 09:12:29AM +0200, Igor Mammedov wrote: >> On Fri, 6 Oct 2017 15:06:57 -0700 >> Alistair Francis <alistair.fran...@xilinx.com> wrote: >> >> > On Fri, Oct 6, 2017 at 4:45 AM, Eduardo Habkost <ehabk...@redhat.com> >> > wrote: >> > > On Fri, Oct 06, 2017 at 10:23:12AM +0200, Igor Mammedov wrote: >> > >> On Thu, 5 Oct 2017 14:09:06 -0300 >> > >> Eduardo Habkost <ehabk...@redhat.com> wrote: >> > >> >> > >> > On Thu, Oct 05, 2017 at 11:04:27AM +0200, Igor Mammedov wrote: >> > >> > > On Wed, 4 Oct 2017 14:39:20 -0700 >> > >> > > Alistair Francis <alistair.fran...@xilinx.com> wrote: >> > >> > > >> > >> > > > On Wed, Oct 4, 2017 at 9:34 AM, Eduardo Habkost >> > >> > > > <ehabk...@redhat.com> wrote: >> > >> > > > > On Wed, Oct 04, 2017 at 03:08:16PM +0200, Igor Mammedov wrote: >> > >> > > > >> On Wed, 4 Oct 2017 09:28:51 -0300 >> > >> > > > >> Eduardo Habkost <ehabk...@redhat.com> wrote: >> > >> > > > >> >> > >> > > > >> > On Wed, Oct 04, 2017 at 01:12:32PM +0200, Igor Mammedov >> > >> > > > >> > wrote: >> > >> > > > >> > > On Tue, 3 Oct 2017 14:41:17 -0700 >> > >> > > > >> > > Alistair Francis <alistair.fran...@xilinx.com> wrote: >> > >> > > > >> > > >> > >> > > > >> > > > On Tue, Oct 3, 2017 at 1:36 PM, Eduardo Habkost >> > >> > > > >> > > > <ehabk...@redhat.com> wrote: >> > >> > > > >> > > > > On Tue, Oct 03, 2017 at 01:05:13PM -0700, Alistair >> > >> > > > >> > > > > Francis wrote: >> > >> > > > >> > > > >> List all possible valid CPU options. >> > >> > > > >> > > > >> >> > >> > > > >> > > > >> Signed-off-by: Alistair Francis >> > >> > > > >> > > > >> <alistair.fran...@xilinx.com> >> > >> > > > >> > > > >> --- >> > >> > > > >> > > > >> >> > >> > > > >> > > > >> hw/arm/xlnx-zcu102.c | 10 ++++++++++ >> > >> > > > >> > > > >> hw/arm/xlnx-zynqmp.c | 16 +++++++++------- >> > >> > > > >> > > > >> include/hw/arm/xlnx-zynqmp.h | 1 + >> > >> > > > >> > > > >> 3 files changed, 20 insertions(+), 7 deletions(-) >> > >> > > > >> > > > >> >> > >> > > > >> > > > >> diff --git a/hw/arm/xlnx-zcu102.c >> > >> > > > >> > > > >> b/hw/arm/xlnx-zcu102.c >> > >> > > > >> > > > >> index 519a16ed98..039649e522 100644 >> > >> > > > >> > > > >> --- a/hw/arm/xlnx-zcu102.c >> > >> > > > >> > > > >> +++ b/hw/arm/xlnx-zcu102.c >> > >> > > > >> > > > >> @@ -98,6 +98,8 @@ static void >> > >> > > > >> > > > >> xlnx_zynqmp_init(XlnxZCU102 *s, MachineState *machine) >> > >> > > > >> > > > >> object_property_add_child(OBJECT(machine), >> > >> > > > >> > > > >> "soc", OBJECT(&s->soc), >> > >> > > > >> > > > >> &error_abort); >> > >> > > > >> > > > >> >> > >> > > > >> > > > >> + object_property_set_str(OBJECT(&s->soc), >> > >> > > > >> > > > >> machine->cpu_type, "cpu-type", >> > >> > > > >> > > > >> + &error_fatal); >> > >> > > > >> > > > > >> > >> > > > >> > > > > Do you have plans to support other CPU types to >> > >> > > > >> > > > > xlnx_zynqmp in >> > >> > > > >> > > > > the future? If not, I wouldn't bother adding the >> > >> > > > >> > > > > cpu-type >> > >> > > > >> > > > > property and the extra boilerplate code if it's always >> > >> > > > >> > > > > going to >> > >> > > > >> > > > > be set to cortex-a53. >> > >> > > > >> > > > >> > >> > > > >> > > > No, it'll always be A53. >> > >> > > > >> > > > >> > >> > > > >> > > > I did think of that, but I also wanted to use the new >> > >> > > > >> > > > option! I also >> > >> > > > >> > > > think there is an advantage in sanely handling users >> > >> > > > >> > > > '-cpu' option, >> > >> > > > >> > > > before now we just ignored it, so I think it still does >> > >> > > > >> > > > give a >> > >> > > > >> > > > benefit. That'll be especially important on the Xilinx >> > >> > > > >> > > > tree (sometimes >> > >> > > > >> > > > people use our machines with a different CPU to >> > >> > > > >> > > > 'benchmark' or test >> > >> > > > >> > > > other CPUs with our CoSimulation setup). So I think it >> > >> > > > >> > > > does make sense >> > >> > > > >> > > > to keep in. >> > >> > > > >> > > if cpu isn't user settable, one could just outright die if >> > >> > > > >> > > cpu_type >> > >> > > > >> > > is not NULL and say that user's CLI is wrong. >> > >> > > > >> > > (i.e. don't give users illusion that they allowed to use >> > >> > > > >> > > '-cpu') >> > >> > > > >> > >> > >> > > > >> > Isn't it exactly what this patch does, by setting: >> > >> > > > >> > mc->default_cpu_type = ARM_CPU_TYPE_NAME("cortex-a53"); >> > >> > > > >> > mc->valid_cpu_types = xlnx_zynqmp_valid_cpus; >> > >> > > > >> > ? >> > >> > > > >> > >> > >> > > > >> > Except that "-cpu cortex-a53" won't die, which is a good >> > >> > > > >> > thing. >> > >> > > > >> allowing "-cpu cortex-a53" here, would allow to use feature >> > >> > > > >> parsing >> > >> > > > >> which weren't allowed or were ignored before if user supplied >> > >> > > > >> '-cpu'. >> > >> > > > >> so I'd more strict and refuse any -cpu and break CLI that >> > >> > > > >> tries to use it >> > >> > > > >> if board has non configurable cpu type. It would be easier to >> > >> > > > >> relax >> > >> > > > >> restriction later if necessary. >> > >> > > > >> >> > >> > > > >> using validate_cpus here just to have users for the new code, >> > >> > > > >> doesn't seem like valid justification and at that it makes >> > >> > > > >> board >> > >> > > > >> code more complex where it's not necessary and build in cpu >> > >> > > > >> type >> > >> > > > >> works just fine. >> > >> > > > > >> > >> > > > > It's up to the board maintainer to decide what's the best >> > >> > > > > option. >> > >> > > > > Both features are independent from each other and can be >> > >> > > > > implemented by machine core. >> > >> > > > >> > >> > > > Noooo! >> > >> > > > >> > >> > > > My hope with this series is that eventually we could hit a state >> > >> > > > where >> > >> > > > every single machine acts the same way with the -cpu option. >> > >> > > > >> > >> > > > I really don't like what we do now where some boards use it, some >> > >> > > > boards error and some boars just ignore the option. I think we >> > >> > > > should >> > >> > > > agree on something and every machine should follow the same flow >> > >> > > > so >> > >> > > > that users know what to expect when they use the -cpu option. >> > >> > > > >> > >> > > > If this means we allow machines to specify they don't support the >> > >> > > > option or only have a single element in the list of supported >> > >> > > > options >> > >> > > > doesn't really matter, but all machines should do the same thing. >> > >> > > > >> > >> > > > > >> > >> > > > > In either case, the valid_cpu_types feature will be still very >> > >> > > > > useful for boards like pxa270 and sa1110, which support -cpu but >> > >> > > > > only with specific families of CPU types (grep for >> > >> > > > > "strncmp(cpu_type"). >> > >> > > > > >> > >> > > > >> >> > >> > > > >> wrt centralized way to refuse -cpu if board doesn't support it, >> > >> > > > >> (which is not really related to this series) following could >> > >> > > > >> be done: >> > >> > > > >> >> > >> > > > >> when cpu_model removal is completely done I plan to replace >> > >> > > > >> vl.c >> > >> > > > >> cpu_parse_cpu_model(machine_class->default_cpu_type, >> > >> > > > >> cpu_model) >> > >> > > > >> with >> > >> > > > >> cpu_parse_cpu_model(DEFAULT_TARGET_CPU_TYPE, cpu_model) >> > >> > > > >> >> > >> > > > >> so that we could drop temporary guard >> > >> > > > >> >> > >> > > > >> if (machine_class->default_cpu_type) { >> > >> > > > > >> > >> > > > > This sounds good to me, even if we don't reject -cpu on any >> > >> > > > > board. >> > >> > > > > >> > >> > > > > >> > >> > > > >> >> > >> > > > >> with that it would be possible to tell from >> > >> > > > >> machine_run_board_init() >> > >> > > > >> that board doesn't provide cpu but user provided '-cpu' >> > >> > > > >> so we would be able to: >> > >> > > > >> if ((machine_class->default_cpu_type == NULL) && >> > >> > > > >> (machine->cpu_type != NULL)) >> > >> > > > >> error_fatal("machine doesn't support -cpu option"); >> > >> > > > > >> > >> > > > > I won't complain too much if a board maintainer really wants to >> > >> > > > > make the board reject -cpu completely, but it's up to them. >> > >> > > > >> > >> > > > I disagree. I think a standard way of doing it is better. At >> > >> > > > least for >> > >> > > > each architecture. The ARM -cpu option is very confusing at the >> > >> > > > moment >> > >> > > > and it really doesn't need to be that bad. >> > >> > > > >> > >> > > > > >> > >> > > > > Personally, I'd prefer to have all boards setting >> > >> > > > > default_cpu_type even if they support only one CPU model, so >> > >> > > > > clients don't need a special case for boards that don't support >> > >> > > > > -cpu. >> > >> > > > >> > >> > > > I agree, I think having one CPU makes more sense. It makes it >> > >> > > > easier >> > >> > > > to add support for more cpus in the future and allows the users >> > >> > > > to use >> > >> > > > the -cpu option without killing QEMU. >> > >> > > I'm considering -cpu option as a legacy one that server 2 purposes >> > >> > > now >> > >> > >> > >> > I'm not sure about "legacy", but the list of purposes looks >> > >> > accurate: >> > >> > >> > >> > > 1: pick cpu type for running instance >> > >> > >> > >> > This one has no replacement yet, so can we really call it legacy? >> > >> not really, it's not going anywhere in near future >> > >> >> > >> > >> > >> > > 2: convert optional features/legacy syntax to global properties >> > >> > > for related cpu type >> > >> > >> > >> > This one has a replacement: -global. But there's a difference >> > >> > between saying "-cpu features are implemented using -global" and >> > >> > "-cpu features are obsoleted by -global". I don't think we can >> > >> > say it's obsolete or legacy unless existing management software >> > >> > is changed to be using something else. >> > >> > >> > >> > >> > >> > > >> > >> > > It plays ok for machines with single type of cpu but doesn't really >> > >> > > scale >> > >> > > to more and doesn't work well nor needed if we were to specify cpus >> > >> > > on CLI >> > >> > > with -device (i.e. build machine from config/CLI) >> > >> > >> > >> > This is a good point. But -cpu is still a useful shortcut for >> > >> > boards that have a single CPU type. What are the arguments we >> > >> > have to get rid of it completely? >> > >> boards that have single cpu type don't need -cpu. since cpu is not >> > >> configurable there. >> > > >> > > They don't need -cpu, but there's no need to reject "-cpu FOO" if >> > > we know FOO is the CPU model used by the board. This is the only >> > > difference between what you propose and what Alistair proposes, >> > > right? >> > > >> > > >> > >> >> > >> >> > >> > > So I would not extend usage '-cpu' to boards that have fixed cpu >> > >> > > type, >> > >> > > because it really useless in that case and confuses users with idea >> > >> > > that >> > >> > > they have ability/need to specify -cpu on fixed cpu board. >> > >> > >> > >> > If they try to choose any other CPU model, they will see an error >> > >> > message explicitly saying only one CPU type is supported. What >> > >> > would be the harm? >> > >> I guess I've already pointed drawbacks from interface point of view, >> > >> from maintainer pov it will be extra code to maintain valid cpus >> > >> vs just 'create_cpu(MY_CPU_TYPE)' >> > >> this patch is vivid example of the case >> > > >> > > With this part I agree. We don't need to add boilerplate code to >> > > board init if the CPU model will always be the same. >> > > >> > > But I would still prefer to do this: >> > > >> > > create_cpu(MY_CPU_TYPE); // at XXX_init() >> > > [...] >> > > static void xxx_class_init(...) { >> > > mc->default_cpu_type = MY_CPU_TYPE; >> > > /* Reason: XXX_init() is hardcoded to MY_CPU_TYPE */ >> > > mc->valid_cpu_types = { MY_CPU_TYPE, NULL }; >> > > } >> > >> > I like this option. It doesn't add much code and I think makes it very >> > clear to users. >> > >> > Another thing to point out is that I see users specifying options to >> > QEMU all the time that QEMU will just ignore. Imagine people see >> > somewhere online that others use '-cpu' and suddenly they think they >> > have to. Having this throw an error that '-cpu' isn't supported in >> > this case (but is in others) will create confusion of when it >> > should/shouldn't be use. I think always allowing it and telling users >> > the supported CPUs clears this up. >> >> patch would look better with what Eduardo suggested above. >> at least it will minimize amount of not need code, so I'd go for it. > > I just see one problem: I don't see an easy way for setting: > mc->valid_cpu_types = { MY_CPU_TYPE, NULL }; > without one additional static variable for holding the array. So > my claim about "only 2 lines of code" is not accurate. > > But we might do this to make the code shorter and simpler on > boards like xlnx_zynqmp: > > 1) Change the default on TYPE_MACHINE to: > mc->valid_cpu_types = { TYPE_CPU, NULL }; > > This will keep the existing behavior for all boards. > > 2) mc->valid_cpu_types=NULL be interpreted as "no CPU model > except the default is accepted" or "-cpu is not accepted" in > machine_run_board_init() (I prefer the former, but both > options would be correct) > > 3) Boards like xlnx_zynqmp could then just do this: > > static void xxx_class_init(...) { > mc->default_cpu_type = MY_CPU_TYPE; > /* Reason: XXX_init() is hardcoded to MY_CPU_TYPE */ > mc->valid_cpu_types = NULL; > }
This is fine with me. I had prepared a patch series with your earlier approach and was about to send it out before I saw this email. I was then going to wait until something was decided but I think I'm just going to send my series out anyway. It has a fix for the wrong CPU in the Raspberry Pi 2 which I think should go in now. We can still continue this discussion though. Thanks, Alistair > > > -- > Eduardo >