Re: [Qemu-devel] [PATCH v13 2/5] i386: Introduce auto_topoext bit to manage topoext

[Moger, Babu]

> -----Original Message-----
> From: Eduardo Habkost [mailto:address@hidden
> Sent: Monday, June 11, 2018 3:46 PM
> To: Moger, Babu <address@hidden>
> Cc: address@hidden; address@hidden; address@hidden;
> address@hidden; address@hidden; address@hidden;
> address@hidden; address@hidden; address@hidden
> Subject: Re: [PATCH v13 2/5] i386: Introduce auto_topoext bit to manage
> topoext
> 
> On Mon, Jun 11, 2018 at 08:25:32PM +0000, Moger, Babu wrote:
> > Hi Eduardo,
> > Planning  to make couple of changes after testing and review.  Let me know
> if I missed something.
> > Will wait for your feedback before the next revision.
> >
> > > -----Original Message-----
> > > From: address@hidden [mailto:kvm-
> address@hidden
> > > On Behalf Of Babu Moger
> > > Sent: Friday, June 8, 2018 5:56 PM
> > > To: address@hidden; address@hidden;
> address@hidden;
> > > address@hidden; address@hidden; address@hidden
> > > Cc: address@hidden; address@hidden; Moger, Babu
> > > <address@hidden>; address@hidden; address@hidden
> > > Subject: [PATCH v13 2/5] i386: Introduce auto_topoext bit to manage
> > > topoext
> > >
> > > Introduce the auto_topoext bit to to control topoext feature.
> > >
> > > Also add new field auto_topoext(in X86CPUDefinition). This will
> > > be used to enable topoext on newer CPU models where topoext can
> > > be supported.
> > >
> > > Signed-off-by: Babu Moger <address@hidden>
> > > ---
> > >  include/hw/i386/pc.h |  4 ++++
> > >  target/i386/cpu.c    | 12 ++++++++++++
> > >  target/i386/cpu.h    |  5 +++++
> > >  3 files changed, 21 insertions(+)
> > >
> > > diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> > > index 04d1f8c..cc30ec3 100644
> > > --- a/include/hw/i386/pc.h
> > > +++ b/include/hw/i386/pc.h
> > > @@ -303,6 +303,10 @@ bool e820_get_entry(int, uint32_t, uint64_t *,
> > > uint64_t *);
> > >          .driver   = TYPE_X86_CPU,\
> > >          .property = "legacy-cache",\
> > >          .value    = "on",\
> > > +    },{\
> > > +        .driver   = TYPE_X86_CPU,\
> > > +        .property = "auto-topoext",\
> > > +        .value    = "off",\
> > >      },
> >
> > We don't need this.  We are already setting this false in
> x86_cpu_properties.
> > But we need to set it "on" for EPYC on PC_COMPAT_3_0 whenever we
> define it.
> > That will be a separate patch. Correct?
> 
> PC_COMPAT_3_0 will exist only on QEMU 3.1.  If you want to define
> something as the default behavior in pc-3.0, just define it as
> the default in the device code, which is exactly what you are
> already doing in x86_cpu_load_def() below.
> 
> In other words, just set auto_topoext=true on the CPU model table
> for EPYC, and it should be enough.
> 
> On PC_COMPAT_2_12, both would work:
>   { TYPE_X86_CPU, "auto-topoext", "off" }
> or
>   { "EPYC" "-" TYPE_X86_CPU, "auto-topoext", "off" }.
> 
> I prefer the latter, but both would work.

Ok. Sure

> 
> 
> >
> > >
> > >  #define PC_COMPAT_2_11 \
> > > diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> > > index 86fb1a4..d3411ed 100644
> > > --- a/target/i386/cpu.c
> > > +++ b/target/i386/cpu.c
> > > @@ -1283,6 +1283,8 @@ struct X86CPUDefinition {
> > >      FeatureWordArray features;
> > >      const char *model_id;
> > >      CPUCaches *cache_info;
> > > +    /* Set it if topoext can be enabled in CPU models */
> > > +    int auto_topoext;
> > >  };
> > >
> > >  static CPUCaches epyc_cache_info = {
> > > @@ -3517,6 +3519,9 @@ static void x86_cpu_load_def(X86CPU *cpu,
> > > X86CPUDefinition *def, Error **errp)
> > >      /* legacy-cache defaults to 'off' if CPU model provides cache info */
> > >      cpu->legacy_cache = !def->cache_info;
> > >
> > > +    /* Set auto_topoext if both machine property and CPU model
> supports it
> > > */
> > > +    cpu->auto_topoext =  cpu->auto_topoext & def->auto_topoext;
> >
> > This could be more appropriate like this.
> >
> >  cpu->auto_topoext =  cpu->auto_topoext && def->auto_topoext;
> 
> cpu->auto_topoext is supposed to be already false, here.  Why not
> just:
>     cpu->auto_topoext = def->auto_topoext;
> ?

Ok. Will do it.

> 
> >
> > > +
> > >      /* Special cases not set in the X86CPUDefinition structs: */
> > >      /* TODO: in-kernel irqchip for hvf */
> > >      if (kvm_enabled()) {
> > > @@ -5382,6 +5387,13 @@ static Property x86_cpu_properties[] = {
> > >      DEFINE_PROP_BOOL("legacy-cache", X86CPU, legacy_cache, true),
> > >
> > >      /*
> > > +     * auto-topoext property will be used to enable topoext feature.
> > > +     * This will be disabled on all the older CPU models. Will be
> > > +     * enabled on newer CPU modeles which can support topology
> extention.
> > > +     */
> > > +     DEFINE_PROP_BOOL("auto-topoext", X86CPU, auto_topoext, false),
> > > +
> > > +    /*
> > >       * From "Requirements for Implementing the Microsoft
> > >       * Hypervisor Interface":
> > >       * https://docs.microsoft.com/en-us/virtualization/hyper-v-on-
> > > windows/reference/tlfs
> > > diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> > > index 89c82be..8783d36 100644
> > > --- a/target/i386/cpu.h
> > > +++ b/target/i386/cpu.h
> > > @@ -1409,6 +1409,11 @@ struct X86CPU {
> > >       */
> > >      bool legacy_cache;
> > >
> > > +    /* Compatibility bits to enable topoext feature on all newer machines
> > > +     * Disabled on older machines. Enabled on newer CPU models
> > > +     */
> > > +    bool auto_topoext;
> > > +
> > >      /* Compatibility bits for old machine types: */
> > >      bool enable_cpuid_0xb;
> > >
> > > --
> > > 1.8.3.1
> >
> 
> --
> Eduardo