Re: [PATCH] x86/cpuid: expose AVX512_4VNNIW and AVX512_4FMAPS features to kvm guest

[He Chen]

On Fri, Oct 28, 2016 at 11:31:05AM +0200, Paolo Bonzini wrote:
> 
> 
> On 28/10/2016 11:12, He Chen wrote:
> > The spec can be found in Intel Software Developer Manual or in
> > Instruction Set Extensions Programming Reference.
> > 
> > Signed-off-by: Luwei Kang <luwei.kang@xxxxxxxxx>
> > Signed-off-by: He Chen <he.chen@xxxxxxxxxxxxxxx>
> > ---
> >  arch/x86/kvm/cpuid.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> > index afa7bbb..328b169 100644
> > --- a/arch/x86/kvm/cpuid.c
> > +++ b/arch/x86/kvm/cpuid.c
> > @@ -376,6 +376,10 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
> >  	/* cpuid 7.0.ecx*/
> >  	const u32 kvm_cpuid_7_0_ecx_x86_features = F(PKU) | 0 /*OSPKE*/;
> >  
> > +	/* cpuid 7.0.edx*/
> > +	const u32 kvm_cpuid_7_0_edx_x86_features =
> > +        0x4 /* AVX512-4VNNIW */ | 0x8 /* AVX512-4FMAPS */;
> 
> Please define the new features in cpufeature.h first.
> 
These 2 new features defined as scattered features in kernel.
In cpufeature.h, there are:
#define X86_FEATURE_AVX512_4VNNIW (7*32+16)
#define X86_FEATURE_AVX512_4FMAPS (7*32+17)

Please see disscusion here:
https://www.mail-archive.com/linux-kernel@xxxxxxxxxxxxxxx/msg1250183.html

Thanks,
-He