Re: [PATCH 1/7] target/i386: Add FEAT_7_1_EDX to adjust feature level

[Tao Su <tao1.su@linux.intel.com>]

On Mon, Jun 26, 2023 at 02:39:15PM +0200, Igor Mammedov wrote:
> On Fri, 16 Jun 2023 11:23:05 +0800
> Tao Su <tao1.su@linux.intel.com> wrote:
> 
> > Considering the case of FEAT_7_1_EAX being 0 and FEAT_7_1_EDX being
> > non-zero,
> Can you clarify when/why that happens?

When start a VM on GraniteRapids using '-cpu host', we can see two leafs CPUID_7_0
and CPUID_7_1 in VM, because both CPUID_7_1_EAX and CPUID_7_1_EDX have non-zero value:
0x00000007 0x01: eax=0x00201c30 edx=0x00004000

But if we minus all FEAT_7_1_EAX features using
'-cpu host,-avx-vnni,-avx512-bf16,-fzrm,-fsrs,-fsrc,-amx-fp16', we can't get CPUID_7_1
leaf even though CPUID_7_1_EDX has non-zero value, so it is necessary to update
cpuid_level_func7 by CPUID_7_1_EDX.

Thanks,
Tao

> 
> > guest may report wrong maximum number sub-leaves in leaf
> > 07H. So add FEAT_7_1_EDX to adjust feature level.
> > 
> > Fixes: eaaa197d5b11 ("target/i386: Add support for AVX-VNNI-INT8 in CPUID
> > enumeration")
> > 
> > Signed-off-by: Tao Su <tao1.su@linux.intel.com>
> > Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
> > ---
> >  target/i386/cpu.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> > index 1242bd541a..e8a70c35d2 100644
> > --- a/target/i386/cpu.c
> > +++ b/target/i386/cpu.c
> > @@ -6778,6 +6778,7 @@ void x86_cpu_expand_features(X86CPU *cpu, Error **errp)
> >          x86_cpu_adjust_feat_level(cpu, FEAT_6_EAX);
> >          x86_cpu_adjust_feat_level(cpu, FEAT_7_0_ECX);
> >          x86_cpu_adjust_feat_level(cpu, FEAT_7_1_EAX);
> > +        x86_cpu_adjust_feat_level(cpu, FEAT_7_1_EDX);
> >          x86_cpu_adjust_feat_level(cpu, FEAT_8000_0001_EDX);
> >          x86_cpu_adjust_feat_level(cpu, FEAT_8000_0001_ECX);
> >          x86_cpu_adjust_feat_level(cpu, FEAT_8000_0007_EDX);
> 
>