Re: [Xen-devel] [PATCH v2 08/10] x86/cpuid: Handle leaf 0xb in guest_cpuid()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 10.03.17 at 17:44, <andrew.cooper3@xxxxxxxxxx> wrote:
> @@ -938,6 +927,21 @@ void guest_cpuid(const struct vcpu *v, uint32_t leaf,
>          }
>          break;
>  
> +    case 0xb:
> +        /*
> +         * In principle, this leaf is Intel-only.  In practice, it is tightly
> +         * coupled with x2apic, and we offer an x2apic-capable APIC emulation
> +         * to guests on AMD hardware as well.
> +         *
> +         * TODO: Rework topology logic.
> +         */
> +        if ( p->basic.x2apic )
> +        {
> +            /* Fix the x2APIC identifier. */
> +            res->d = v->vcpu_id * 2;
> +        }
> +        break;

The SDM says that ECX[7:0] output matches the input. I think you
want to mimic that (not doing so would imo be acceptable only if
you returned all zeros uniformly).

With that taken care of
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Jan


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