Re: [libvirt] [PATCH v5 1/2] vl.c deprecate incorrect CPUs topology
On 9/10/18 12:49 PM, Eduardo Habkost wrote:
I was considering something like this:
Signed-off-by: Eduardo Habkost
---
diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi
index 060e015be6..74f6a64b8b 100644
--- a/qemu-deprecated.texi
+++ b/qemu-options.hx
@@ -155,8 +155,13 @@ to 4.
For the PC target, the number of @var{cores} per socket, the number
of @var{threads} per cores and the total number of @var{sockets} can be
specified. Missing values will be computed. If any on the three values is
while here, s/on/of/
-given, the total number of CPUs @var{n} can be omitted. @var{maxcpus}
-specifies the maximum number of hotpluggable CPUs.
+given, the total number of CPUs @var{n} can be omitted.
+
+@var{maxcpus} specifies the maximum number of hotpluggable CPUs
+and should be equal to @math{@var{sockets} * @var{cores} * @var{threads}}
+(even if @var{sockets}, @var{cores}, or @var{threads} is omitted
+and computed automatically).
+
ETEXI
DEF("numa", HAS_ARG, QEMU_OPTION_numa,
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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Re: [libvirt] [PATCH v5 1/2] vl.c deprecate incorrect CPUs topology
On 9/4/18 8:22 AM, Igor Mammedov wrote: -smp [cpus],sockets/cores/threads[,maxcpus] should describe topology so that total number of logical CPUs [sockets * cores * threads] would be equal to [maxcpus], however historically we didn't have such check in QEMU and it is possible to start VM with an invalid topology. Deprecate invalid options combination so we can make sure that the topology VM started with is always correct in the future. Users with an invalid sockets/cores/threads/maxcpus values should fix their CLI to make sure that [sockets * cores * threads] == [maxcpus] Signed-off-by: Igor Mammedov --- +@subsection -smp X,[socket=a,core=b,thread=c],maxcpus=Y (since 3.1) + +CPU topology properties should describe whole machine topology including +possible CPUs, but historically it was possible to start QEMU with +an incorrect topology where + sockets * cores * threads >= X && X < maxcpus +which could lead to an incorrect topology enumeration by the guest. +Support for invalid topologies will be removed, the user must ensure +topologies described with -smp include all possible cpus, i.e. + sockets * cores * threads == maxcpus +Note: it's assumed that maxcpus value must be multiple of the topology +options present on command line to avoid creating an invalid topology. +If maxcpus isn't be multiple of present topology options then the condition s/be/a/ +(sockets * cores * threads == maxcpus) can't be satisfied and it will +trigger deprecation warning which later will be converted to a error. a/a error/an error/ +If you get deprecation warning it's recommended to explicitly specify s/get/get a/ +a correct topology to make warning go away and ensure that it will +continue working in the future. + -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [PATCH v5 1/2] vl.c deprecate incorrect CPUs topology
On Thu, Sep 06, 2018 at 10:02:13AM +0200, Igor Mammedov wrote:
> On Wed, 5 Sep 2018 10:45:12 -0300
> Eduardo Habkost wrote:
>
> > On Wed, Sep 05, 2018 at 11:25:11AM +0200, Igor Mammedov wrote:
> > > On Tue, 4 Sep 2018 23:12:55 -0300
> > > Eduardo Habkost wrote:
> > >
> > > > On Tue, Sep 04, 2018 at 03:22:35PM +0200, Igor Mammedov wrote:
> > > > > -smp [cpus],sockets/cores/threads[,maxcpus] should describe topology
> > > > > so that total number of logical CPUs [sockets * cores * threads]
> > > > > would be equal to [maxcpus], however historically we didn't have
> > > > > such check in QEMU and it is possible to start VM with an invalid
> > > > > topology.
> > > > > Deprecate invalid options combination so we can make sure that
> > > > > the topology VM started with is always correct in the future.
> > > > > Users with an invalid sockets/cores/threads/maxcpus values should
> > > > > fix their CLI to make sure that
> > > > >[sockets * cores * threads] == [maxcpus]
> > > > >
> > > > > Signed-off-by: Igor Mammedov
> > > > > ---
> > > > > v5:
> > > > > - extend deprecation doc, adding that maxcpus should be multiple of
> > > > > present on CLI [sockets/cores/threads] options
> > > > > (Eduardo Habkost )
> > > > > v4:
> > > > > - missed dot comment, fix it with s/./,/ (Andrew Jones
> > > > > )
> > > > > v3:
> > > > > - more spelling fixes (Andrew Jones )
> > > > > - place deprecation check after (sockets * cores * threads >
> > > > > max_cpus) check
> > > > > (Eduardo Habkost )
> > > > > v2:
> > > > > - spelling&&co fixes (Andrew Jones )
> > > > > ---
> > > > > qemu-deprecated.texi | 19 +++
> > > > > vl.c | 7 +++
> > > > > 2 files changed, 26 insertions(+)
> > > > >
> > > > > diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi
> > > > > index 87212b6..827c3ce 100644
> > > > > --- a/qemu-deprecated.texi
> > > > > +++ b/qemu-deprecated.texi
> > > > > @@ -159,6 +159,25 @@ The 'file' driver for drives is no longer
> > > > > appropriate for character or host
> > > > > devices and will only accept regular files (S_IFREG). The correct
> > > > > driver
> > > > > for these file types is 'host_cdrom' or 'host_device' as appropriate.
> > > > >
> > > > > +@subsection -smp X,[socket=a,core=b,thread=c],maxcpus=Y (since 3.1)
> > > >
> > > > Minor: I suggest using @var markup, or maybe just use
> > > > "-smp (invalid topologies) (since 3.1)" as subsection title for
> > > > simplicity?
> > > >
> > > > > +
> > > > > +CPU topology properties should describe whole machine topology
> > > > > including
> > > > > +possible CPUs, but historically it was possible to start QEMU with
> > > > > +an incorrect topology where
> > > > > + sockets * cores * threads >= X && X < maxcpus
> > > >
> > > > Minor: this line formatting is lost on the HTML output. I
> > > > suggest using @var and/or @math.
> > > >
> > > > Minor: I suggest not using C syntax.
> > > >
> > > > i.e. use something like:
> > > >
> > > > @math{@var{n} <= @var{sockets} * @var{cores} * @var{threads} <
> > > > @var{maxcpus}},
> > > >
> > > > > +which could lead to an incorrect topology enumeration by the guest.
> > > > > +Support for invalid topologies will be removed, the user must ensure
> > > > > +topologies described with -smp include all possible cpus, i.e.
> > > > > + sockets * cores * threads == maxcpus
> > > >
> > > > Minor: same as above. I suggest:
> > > >
> > > > @math{@var{sockets} * @var{cores} * @var{threads} = @var{maxcpus}}.
> > > >
> > > >
> > > > > +Note: it's assumed that maxcpus value must be multiple of the
> > > > > topology
> > > > > +options present on command line to avoid creating an invalid
> > > > > topology.
> > > > > +If maxcpus isn't be multiple of present topology options then the
> > > > > condition
> > > > > +(sockets * cores * threads == maxcpus) can't be satisfied and it will
> > > > > +trigger deprecation warning which later will be converted to a error.
> > > > > +If you get deprecation warning it's recommended to explicitly specify
> > > > > +a correct topology to make warning go away and ensure that it will
> > > > > +continue working in the future.
> > > >
> > > > I don't understand the purpose of the "Note:" section. It seems to
> > > > duplicate
> > > > what was already said in the lines above it. Can we just remove it?
> > > Well, didn't I say that no additional explanation needed in v4?
> > > Note section was added per your suggestion to explicitly say that maxcpus
> > > should be multiple of options present on CLI.
> >
> > You are right: I did ask for additional clarification on the
> > documentation, because it was not clear that the warning can
> > still appear even if some of the sockets/cores/threads options
> > were omitted. The note didn't make that clearer to me, though.
> I can respin if necessary (we are not in hurry so no need to merge
> something that would be removed immediately).
> Cou
Re: [libvirt] [PATCH v5 1/2] vl.c deprecate incorrect CPUs topology
On Wed, 5 Sep 2018 10:45:12 -0300
Eduardo Habkost wrote:
> On Wed, Sep 05, 2018 at 11:25:11AM +0200, Igor Mammedov wrote:
> > On Tue, 4 Sep 2018 23:12:55 -0300
> > Eduardo Habkost wrote:
> >
> > > On Tue, Sep 04, 2018 at 03:22:35PM +0200, Igor Mammedov wrote:
> > > > -smp [cpus],sockets/cores/threads[,maxcpus] should describe topology
> > > > so that total number of logical CPUs [sockets * cores * threads]
> > > > would be equal to [maxcpus], however historically we didn't have
> > > > such check in QEMU and it is possible to start VM with an invalid
> > > > topology.
> > > > Deprecate invalid options combination so we can make sure that
> > > > the topology VM started with is always correct in the future.
> > > > Users with an invalid sockets/cores/threads/maxcpus values should
> > > > fix their CLI to make sure that
> > > >[sockets * cores * threads] == [maxcpus]
> > > >
> > > > Signed-off-by: Igor Mammedov
> > > > ---
> > > > v5:
> > > > - extend deprecation doc, adding that maxcpus should be multiple of
> > > > present on CLI [sockets/cores/threads] options
> > > > (Eduardo Habkost )
> > > > v4:
> > > > - missed dot comment, fix it with s/./,/ (Andrew Jones
> > > > )
> > > > v3:
> > > > - more spelling fixes (Andrew Jones )
> > > > - place deprecation check after (sockets * cores * threads >
> > > > max_cpus) check
> > > > (Eduardo Habkost )
> > > > v2:
> > > > - spelling&&co fixes (Andrew Jones )
> > > > ---
> > > > qemu-deprecated.texi | 19 +++
> > > > vl.c | 7 +++
> > > > 2 files changed, 26 insertions(+)
> > > >
> > > > diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi
> > > > index 87212b6..827c3ce 100644
> > > > --- a/qemu-deprecated.texi
> > > > +++ b/qemu-deprecated.texi
> > > > @@ -159,6 +159,25 @@ The 'file' driver for drives is no longer
> > > > appropriate for character or host
> > > > devices and will only accept regular files (S_IFREG). The correct
> > > > driver
> > > > for these file types is 'host_cdrom' or 'host_device' as appropriate.
> > > >
> > > > +@subsection -smp X,[socket=a,core=b,thread=c],maxcpus=Y (since 3.1)
> > >
> > > Minor: I suggest using @var markup, or maybe just use
> > > "-smp (invalid topologies) (since 3.1)" as subsection title for
> > > simplicity?
> > >
> > > > +
> > > > +CPU topology properties should describe whole machine topology
> > > > including
> > > > +possible CPUs, but historically it was possible to start QEMU with
> > > > +an incorrect topology where
> > > > + sockets * cores * threads >= X && X < maxcpus
> > >
> > > Minor: this line formatting is lost on the HTML output. I
> > > suggest using @var and/or @math.
> > >
> > > Minor: I suggest not using C syntax.
> > >
> > > i.e. use something like:
> > >
> > > @math{@var{n} <= @var{sockets} * @var{cores} * @var{threads} <
> > > @var{maxcpus}},
> > >
> > > > +which could lead to an incorrect topology enumeration by the guest.
> > > > +Support for invalid topologies will be removed, the user must ensure
> > > > +topologies described with -smp include all possible cpus, i.e.
> > > > + sockets * cores * threads == maxcpus
> > >
> > > Minor: same as above. I suggest:
> > >
> > > @math{@var{sockets} * @var{cores} * @var{threads} = @var{maxcpus}}.
> > >
> > >
> > > > +Note: it's assumed that maxcpus value must be multiple of the topology
> > > > +options present on command line to avoid creating an invalid topology.
> > > > +If maxcpus isn't be multiple of present topology options then the
> > > > condition
> > > > +(sockets * cores * threads == maxcpus) can't be satisfied and it will
> > > > +trigger deprecation warning which later will be converted to a error.
> > > > +If you get deprecation warning it's recommended to explicitly specify
> > > > +a correct topology to make warning go away and ensure that it will
> > > > +continue working in the future.
> > >
> > > I don't understand the purpose of the "Note:" section. It seems to
> > > duplicate
> > > what was already said in the lines above it. Can we just remove it?
> > Well, didn't I say that no additional explanation needed in v4?
> > Note section was added per your suggestion to explicitly say that maxcpus
> > should be multiple of options present on CLI.
>
> You are right: I did ask for additional clarification on the
> documentation, because it was not clear that the warning can
> still appear even if some of the sockets/cores/threads options
> were omitted. The note didn't make that clearer to me, though.
I can respin if necessary (we are not in hurry so no need to merge
something that would be removed immediately).
Could you suggest a text for clarification for me to include on respin?
>
> In either case, this can be done on a follow-up patch if
> necessary.
>
> Reviewed-by: Eduardo Habkost
>
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Re: [libvirt] [PATCH v5 1/2] vl.c deprecate incorrect CPUs topology
On Wed, Sep 05, 2018 at 11:25:11AM +0200, Igor Mammedov wrote:
> On Tue, 4 Sep 2018 23:12:55 -0300
> Eduardo Habkost wrote:
>
> > On Tue, Sep 04, 2018 at 03:22:35PM +0200, Igor Mammedov wrote:
> > > -smp [cpus],sockets/cores/threads[,maxcpus] should describe topology
> > > so that total number of logical CPUs [sockets * cores * threads]
> > > would be equal to [maxcpus], however historically we didn't have
> > > such check in QEMU and it is possible to start VM with an invalid
> > > topology.
> > > Deprecate invalid options combination so we can make sure that
> > > the topology VM started with is always correct in the future.
> > > Users with an invalid sockets/cores/threads/maxcpus values should
> > > fix their CLI to make sure that
> > >[sockets * cores * threads] == [maxcpus]
> > >
> > > Signed-off-by: Igor Mammedov
> > > ---
> > > v5:
> > > - extend deprecation doc, adding that maxcpus should be multiple of
> > > present on CLI [sockets/cores/threads] options
> > > (Eduardo Habkost )
> > > v4:
> > > - missed dot comment, fix it with s/./,/ (Andrew Jones
> > > )
> > > v3:
> > > - more spelling fixes (Andrew Jones )
> > > - place deprecation check after (sockets * cores * threads > max_cpus)
> > > check
> > > (Eduardo Habkost )
> > > v2:
> > > - spelling&&co fixes (Andrew Jones )
> > > ---
> > > qemu-deprecated.texi | 19 +++
> > > vl.c | 7 +++
> > > 2 files changed, 26 insertions(+)
> > >
> > > diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi
> > > index 87212b6..827c3ce 100644
> > > --- a/qemu-deprecated.texi
> > > +++ b/qemu-deprecated.texi
> > > @@ -159,6 +159,25 @@ The 'file' driver for drives is no longer
> > > appropriate for character or host
> > > devices and will only accept regular files (S_IFREG). The correct driver
> > > for these file types is 'host_cdrom' or 'host_device' as appropriate.
> > >
> > > +@subsection -smp X,[socket=a,core=b,thread=c],maxcpus=Y (since 3.1)
> >
> > Minor: I suggest using @var markup, or maybe just use
> > "-smp (invalid topologies) (since 3.1)" as subsection title for simplicity?
> >
> > > +
> > > +CPU topology properties should describe whole machine topology including
> > > +possible CPUs, but historically it was possible to start QEMU with
> > > +an incorrect topology where
> > > + sockets * cores * threads >= X && X < maxcpus
> >
> > Minor: this line formatting is lost on the HTML output. I
> > suggest using @var and/or @math.
> >
> > Minor: I suggest not using C syntax.
> >
> > i.e. use something like:
> >
> > @math{@var{n} <= @var{sockets} * @var{cores} * @var{threads} <
> > @var{maxcpus}},
> >
> > > +which could lead to an incorrect topology enumeration by the guest.
> > > +Support for invalid topologies will be removed, the user must ensure
> > > +topologies described with -smp include all possible cpus, i.e.
> > > + sockets * cores * threads == maxcpus
> >
> > Minor: same as above. I suggest:
> >
> > @math{@var{sockets} * @var{cores} * @var{threads} = @var{maxcpus}}.
> >
> >
> > > +Note: it's assumed that maxcpus value must be multiple of the topology
> > > +options present on command line to avoid creating an invalid topology.
> > > +If maxcpus isn't be multiple of present topology options then the
> > > condition
> > > +(sockets * cores * threads == maxcpus) can't be satisfied and it will
> > > +trigger deprecation warning which later will be converted to a error.
> > > +If you get deprecation warning it's recommended to explicitly specify
> > > +a correct topology to make warning go away and ensure that it will
> > > +continue working in the future.
> >
> > I don't understand the purpose of the "Note:" section. It seems to
> > duplicate
> > what was already said in the lines above it. Can we just remove it?
> Well, didn't I say that no additional explanation needed in v4?
> Note section was added per your suggestion to explicitly say that maxcpus
> should be multiple of options present on CLI.
You are right: I did ask for additional clarification on the
documentation, because it was not clear that the warning can
still appear even if some of the sockets/cores/threads options
were omitted. The note didn't make that clearer to me, though.
In either case, this can be done on a follow-up patch if
necessary.
Reviewed-by: Eduardo Habkost
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Re: [libvirt] [PATCH v5 1/2] vl.c deprecate incorrect CPUs topology
On Tue, 4 Sep 2018 23:12:55 -0300
Eduardo Habkost wrote:
> On Tue, Sep 04, 2018 at 03:22:35PM +0200, Igor Mammedov wrote:
> > -smp [cpus],sockets/cores/threads[,maxcpus] should describe topology
> > so that total number of logical CPUs [sockets * cores * threads]
> > would be equal to [maxcpus], however historically we didn't have
> > such check in QEMU and it is possible to start VM with an invalid
> > topology.
> > Deprecate invalid options combination so we can make sure that
> > the topology VM started with is always correct in the future.
> > Users with an invalid sockets/cores/threads/maxcpus values should
> > fix their CLI to make sure that
> >[sockets * cores * threads] == [maxcpus]
> >
> > Signed-off-by: Igor Mammedov
> > ---
> > v5:
> > - extend deprecation doc, adding that maxcpus should be multiple of
> > present on CLI [sockets/cores/threads] options
> > (Eduardo Habkost )
> > v4:
> > - missed dot comment, fix it with s/./,/ (Andrew Jones
> > )
> > v3:
> > - more spelling fixes (Andrew Jones )
> > - place deprecation check after (sockets * cores * threads > max_cpus)
> > check
> > (Eduardo Habkost )
> > v2:
> > - spelling&&co fixes (Andrew Jones )
> > ---
> > qemu-deprecated.texi | 19 +++
> > vl.c | 7 +++
> > 2 files changed, 26 insertions(+)
> >
> > diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi
> > index 87212b6..827c3ce 100644
> > --- a/qemu-deprecated.texi
> > +++ b/qemu-deprecated.texi
> > @@ -159,6 +159,25 @@ The 'file' driver for drives is no longer appropriate
> > for character or host
> > devices and will only accept regular files (S_IFREG). The correct driver
> > for these file types is 'host_cdrom' or 'host_device' as appropriate.
> >
> > +@subsection -smp X,[socket=a,core=b,thread=c],maxcpus=Y (since 3.1)
>
> Minor: I suggest using @var markup, or maybe just use
> "-smp (invalid topologies) (since 3.1)" as subsection title for simplicity?
>
> > +
> > +CPU topology properties should describe whole machine topology including
> > +possible CPUs, but historically it was possible to start QEMU with
> > +an incorrect topology where
> > + sockets * cores * threads >= X && X < maxcpus
>
> Minor: this line formatting is lost on the HTML output. I
> suggest using @var and/or @math.
>
> Minor: I suggest not using C syntax.
>
> i.e. use something like:
>
> @math{@var{n} <= @var{sockets} * @var{cores} * @var{threads} <
> @var{maxcpus}},
>
> > +which could lead to an incorrect topology enumeration by the guest.
> > +Support for invalid topologies will be removed, the user must ensure
> > +topologies described with -smp include all possible cpus, i.e.
> > + sockets * cores * threads == maxcpus
>
> Minor: same as above. I suggest:
>
> @math{@var{sockets} * @var{cores} * @var{threads} = @var{maxcpus}}.
>
>
> > +Note: it's assumed that maxcpus value must be multiple of the topology
> > +options present on command line to avoid creating an invalid topology.
> > +If maxcpus isn't be multiple of present topology options then the condition
> > +(sockets * cores * threads == maxcpus) can't be satisfied and it will
> > +trigger deprecation warning which later will be converted to a error.
> > +If you get deprecation warning it's recommended to explicitly specify
> > +a correct topology to make warning go away and ensure that it will
> > +continue working in the future.
>
> I don't understand the purpose of the "Note:" section. It seems to duplicate
> what was already said in the lines above it. Can we just remove it?
Well, didn't I say that no additional explanation needed in v4?
Note section was added per your suggestion to explicitly say that maxcpus
should be multiple of options present on CLI.
>
> These are just suggestions in case you are going to respin the series, not
> blockers.
>
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Re: [libvirt] [PATCH v5 1/2] vl.c deprecate incorrect CPUs topology
On Tue, Sep 04, 2018 at 03:22:35PM +0200, Igor Mammedov wrote:
> -smp [cpus],sockets/cores/threads[,maxcpus] should describe topology
> so that total number of logical CPUs [sockets * cores * threads]
> would be equal to [maxcpus], however historically we didn't have
> such check in QEMU and it is possible to start VM with an invalid
> topology.
> Deprecate invalid options combination so we can make sure that
> the topology VM started with is always correct in the future.
> Users with an invalid sockets/cores/threads/maxcpus values should
> fix their CLI to make sure that
>[sockets * cores * threads] == [maxcpus]
>
> Signed-off-by: Igor Mammedov
> ---
> v5:
> - extend deprecation doc, adding that maxcpus should be multiple of
> present on CLI [sockets/cores/threads] options
> (Eduardo Habkost )
> v4:
> - missed dot comment, fix it with s/./,/ (Andrew Jones )
> v3:
> - more spelling fixes (Andrew Jones )
> - place deprecation check after (sockets * cores * threads > max_cpus) check
> (Eduardo Habkost )
> v2:
> - spelling&&co fixes (Andrew Jones )
> ---
> qemu-deprecated.texi | 19 +++
> vl.c | 7 +++
> 2 files changed, 26 insertions(+)
>
> diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi
> index 87212b6..827c3ce 100644
> --- a/qemu-deprecated.texi
> +++ b/qemu-deprecated.texi
> @@ -159,6 +159,25 @@ The 'file' driver for drives is no longer appropriate
> for character or host
> devices and will only accept regular files (S_IFREG). The correct driver
> for these file types is 'host_cdrom' or 'host_device' as appropriate.
>
> +@subsection -smp X,[socket=a,core=b,thread=c],maxcpus=Y (since 3.1)
Minor: I suggest using @var markup, or maybe just use
"-smp (invalid topologies) (since 3.1)" as subsection title for simplicity?
> +
> +CPU topology properties should describe whole machine topology including
> +possible CPUs, but historically it was possible to start QEMU with
> +an incorrect topology where
> + sockets * cores * threads >= X && X < maxcpus
Minor: this line formatting is lost on the HTML output. I
suggest using @var and/or @math.
Minor: I suggest not using C syntax.
i.e. use something like:
@math{@var{n} <= @var{sockets} * @var{cores} * @var{threads} < @var{maxcpus}},
> +which could lead to an incorrect topology enumeration by the guest.
> +Support for invalid topologies will be removed, the user must ensure
> +topologies described with -smp include all possible cpus, i.e.
> + sockets * cores * threads == maxcpus
Minor: same as above. I suggest:
@math{@var{sockets} * @var{cores} * @var{threads} = @var{maxcpus}}.
> +Note: it's assumed that maxcpus value must be multiple of the topology
> +options present on command line to avoid creating an invalid topology.
> +If maxcpus isn't be multiple of present topology options then the condition
> +(sockets * cores * threads == maxcpus) can't be satisfied and it will
> +trigger deprecation warning which later will be converted to a error.
> +If you get deprecation warning it's recommended to explicitly specify
> +a correct topology to make warning go away and ensure that it will
> +continue working in the future.
I don't understand the purpose of the "Note:" section. It seems to duplicate
what was already said in the lines above it. Can we just remove it?
These are just suggestions in case you are going to respin the series, not
blockers.
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[libvirt] [PATCH v5 1/2] vl.c deprecate incorrect CPUs topology
-smp [cpus],sockets/cores/threads[,maxcpus] should describe topology
so that total number of logical CPUs [sockets * cores * threads]
would be equal to [maxcpus], however historically we didn't have
such check in QEMU and it is possible to start VM with an invalid
topology.
Deprecate invalid options combination so we can make sure that
the topology VM started with is always correct in the future.
Users with an invalid sockets/cores/threads/maxcpus values should
fix their CLI to make sure that
[sockets * cores * threads] == [maxcpus]
Signed-off-by: Igor Mammedov
---
v5:
- extend deprecation doc, adding that maxcpus should be multiple of
present on CLI [sockets/cores/threads] options
(Eduardo Habkost )
v4:
- missed dot comment, fix it with s/./,/ (Andrew Jones )
v3:
- more spelling fixes (Andrew Jones )
- place deprecation check after (sockets * cores * threads > max_cpus) check
(Eduardo Habkost )
v2:
- spelling&&co fixes (Andrew Jones )
---
qemu-deprecated.texi | 19 +++
vl.c | 7 +++
2 files changed, 26 insertions(+)
diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi
index 87212b6..827c3ce 100644
--- a/qemu-deprecated.texi
+++ b/qemu-deprecated.texi
@@ -159,6 +159,25 @@ The 'file' driver for drives is no longer appropriate for
character or host
devices and will only accept regular files (S_IFREG). The correct driver
for these file types is 'host_cdrom' or 'host_device' as appropriate.
+@subsection -smp X,[socket=a,core=b,thread=c],maxcpus=Y (since 3.1)
+
+CPU topology properties should describe whole machine topology including
+possible CPUs, but historically it was possible to start QEMU with
+an incorrect topology where
+ sockets * cores * threads >= X && X < maxcpus
+which could lead to an incorrect topology enumeration by the guest.
+Support for invalid topologies will be removed, the user must ensure
+topologies described with -smp include all possible cpus, i.e.
+ sockets * cores * threads == maxcpus
+Note: it's assumed that maxcpus value must be multiple of the topology
+options present on command line to avoid creating an invalid topology.
+If maxcpus isn't be multiple of present topology options then the condition
+(sockets * cores * threads == maxcpus) can't be satisfied and it will
+trigger deprecation warning which later will be converted to a error.
+If you get deprecation warning it's recommended to explicitly specify
+a correct topology to make warning go away and ensure that it will
+continue working in the future.
+
@section QEMU Machine Protocol (QMP) commands
@subsection block-dirty-bitmap-add "autoload" parameter (since 2.12.0)
diff --git a/vl.c b/vl.c
index 5ba06ad..7fd700e 100644
--- a/vl.c
+++ b/vl.c
@@ -1246,6 +1246,13 @@ static void smp_parse(QemuOpts *opts)
exit(1);
}
+if (sockets * cores * threads != max_cpus) {
+warn_report("Invalid CPU topology deprecated: "
+"sockets (%u) * cores (%u) * threads (%u) "
+"!= maxcpus (%u)",
+sockets, cores, threads, max_cpus);
+}
+
smp_cpus = cpus;
smp_cores = cores;
smp_threads = threads;
--
2.7.4
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