Re: [PATCH v2 15/15] KVM: x86/cpuid: Advertise Arch LBR feature in CPUID

[Yang, Weijiang]

On 12/22/2022 7:03 PM, Like Xu wrote:
> On 25/11/2022 12:06 pm, Yang Weijiang wrote:
> > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> > index 85e3df6217af..60b3c591d462 100644
> > --- a/arch/x86/kvm/cpuid.c
> > +++ b/arch/x86/kvm/cpuid.c
> > @@ -134,6 +134,19 @@ static int kvm_check_cpuid(struct kvm_vcpu *vcpu,
> >           if (vaddr_bits != 48 && vaddr_bits != 57 && vaddr_bits != 0)
> >               return -EINVAL;
> >       }
> > +    if (kvm_cpu_cap_has(X86_FEATURE_ARCH_LBR)) {
> > +        best = cpuid_entry2_find(entries, nent, 0x1c, 0);
> > +        if (best) {
> > +            unsigned int eax, ebx, ecx, edx;
> > +
> > +            /* Reject user-space CPUID if depth is different from 
> > host's.*/
>
> Try to verify this in the KVM selftest, as this behavior is different 
> from the host.


Will do it.



> > +            cpuid_count(0x1c, 0, &eax, &ebx, &ecx, &edx); > +
> > +            if ((eax & 0xff) &&
> > +                (best->eax & 0xff) != BIT(fls(eax & 0xff) - 1))
> > +                return -EINVAL;
> > +        }
> > +    }