Re: [PATCH v3 2/2] x86/kvm: Expose new features for supported cpuid

[Zhang, Cathy]

On 8/10/2020 1:14 AM, Paolo Bonzini wrote:
> On 09/08/20 09:47, Cathy Zhang wrote:
> > Expose the SERIALIZE and TSX Suspend Load Address Tracking
> > features in KVM CPUID, so when running on processors which
> > support them, KVM could pass this information to guests and
> > they can make use of these features accordingly.
> >
> > SERIALIZE is a faster serializing instruction which does not modify
> > registers, arithmetic flags or memory, will not cause VM exit. It's
> > availability is indicated by CPUID.(EAX=7,ECX=0):ECX[bit 14].
> >
> > TSX suspend load tracking instruction aims to give a way to choose
> > which memory accesses do not need to be tracked in the TSX read set.
> > It's availability is indicated as CPUID.(EAX=7,ECX=0):EDX[bit 16].
> >
> > Those instructions are currently documented in the the latest "extensions"
> > manual (ISE). It will appear in the "main" manual (SDM) in the future.
> >
> > Signed-off-by: Cathy Zhang <cathy.zhang@xxxxxxxxx>
> > Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
> > ---
> > Changes since v2:
> >   * Merge two patches into a single one. (Luck, Tony)
> >   * Add overview introduction for features. (Sean Christopherson)
> >   * Refactor commit message to explain why expose feature bits. (Luck, Tony)
> > ---
> >   arch/x86/kvm/cpuid.c | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> > index 8a294f9..dcf48cc 100644
> > --- a/arch/x86/kvm/cpuid.c
> > +++ b/arch/x86/kvm/cpuid.c
> > @@ -341,7 +341,8 @@ void kvm_set_cpu_caps(void)
> >   	kvm_cpu_cap_mask(CPUID_7_EDX,
> >   		F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) |
> >   		F(SPEC_CTRL_SSBD) | F(ARCH_CAPABILITIES) | F(INTEL_STIBP) |
> > -		F(MD_CLEAR) | F(AVX512_VP2INTERSECT) | F(FSRM)
> > +		F(MD_CLEAR) | F(AVX512_VP2INTERSECT) | F(FSRM) |
> > +		F(SERIALIZE) | F(TSXLDTRK)
> >   	);
> >   
> >   	/* TSC_ADJUST and ARCH_CAPABILITIES are emulated in software. */
> TSXLDTRK is not going to be in 5.9 as far as I can see, so I split back
> again the patches (this is why I prefer them to be split, sorry Tony :))
> and committed the SERIALIZE part.
>
> Paolo

Hello Paolo,

As you suggest, I will split the kvm patch into two parts, SERIALIZE and 
TSXLDTRK, and this series will include three patches then, 2 kvm patches 
and 1 kernel patch. SERIALIZE could get merged into 5.9, but TSXLDTRK 
should wait for the next release. I just want to double confirm with 
you, please help correct me if I'm wrong.