Re: [Xen-devel] [PATCH v2 2/2] x86/hvm: add support for pcommit instruction

[Haozhong Zhang <haozhong.zhang@xxxxxxxxx>]

On 01/08/16 00:54, Jan Beulich wrote:
> >>> On 08.01.16 at 02:15, <haozhong.zhang@xxxxxxxxx> wrote:
> > On 01/07/16 06:53, Jan Beulich wrote:
> >> >>> On 30.12.15 at 12:48, <haozhong.zhang@xxxxxxxxx> wrote:
> >> > --- a/xen/arch/x86/hvm/hvm.c
> >> > +++ b/xen/arch/x86/hvm/hvm.c
> >> > @@ -4605,6 +4605,9 @@ void hvm_cpuid(unsigned int input, unsigned int 
> >> > *eax, 
> > unsigned int *ebx,
> >> >  
> >> >              if ( !cpu_has_clwb )
> >> >                  *ebx &= ~cpufeat_mask(X86_FEATURE_CLWB);
> >> > +
> >> > +            if ( !cpu_has_pcommit )
> >> > +                *ebx &= ~cpufeat_mask(X86_FEATURE_PCOMMIT);
> >> 
> >> Other than for patch 1, this not only need to stay, but needs to be
> >> extended along the lines of X86_FEATURE_MPX handling.
> >>
> > 
> > In section "PCOMMIT - Virtualization Support" of Intel Architecture
> > Instruction Set Extensions Programming Reference, it says
> > 
> >     IA32_VMX_PROCBASED_CTLS2[53] (which enumerates support for the
> >     1-setting of âPCOMMIT exitingâ) is always the same as
> >     CPUID.07H:EBX.PCOMMIT[bit 22].
> > 
> > so checking cpu_has_pcommit is enough here.
> 
> Even if the documentation says so, I think it is appropriate (as
> indicated at the very least to match with MPX handling) to add
> the check (here or elsewhere), just to make obvious that both
> are a prereq.
> 
> Jan

OK, I'll modify in the next version.

Haozhong

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