Re: [PATCH v3 06/21] KVM:x86: Report XSS as to-be-saved if there are supported features

[Yang, Weijiang]

On 5/24/2023 3:06 PM, Chao Gao wrote:
> On Thu, May 11, 2023 at 12:08:42AM -0400, Yang Weijiang wrote:
> > From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> >
> > Add MSR_IA32_XSS to the list of MSRs reported to userspace if
> > supported_xss is non-zero, i.e. KVM supports at least one XSS based
> > feature.
> The changelog doesn't match what the patch does.
>
> Do you need to check if supported_xss is non-zero in kvm_probe_msr_to_save(),
> e.g.,
>          case MSR_IA32_XSS:
>                  if (!kvm_caps.supported_xss)
>                          return;
>                  break;

I looked back the history of this patch, there's similar check 
originally, however it's lost

during following rebases. I'll add it back. Thanks for pointing it out!

> > Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> > Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
> > ---
> > arch/x86/kvm/x86.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index e7f78fe79b32..33a780fe820b 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -1454,6 +1454,7 @@ static const u32 msrs_to_save_base[] = {
> > 	MSR_IA32_UMWAIT_CONTROL,
> >
> > 	MSR_IA32_XFD, MSR_IA32_XFD_ERR,
> > +	MSR_IA32_XSS,
> > };
> >
> > static const u32 msrs_to_save_pmu[] = {
> > --
> > 2.27.0