Re: [Xen-devel] [PATCH for-4.8 2/2] x86/traps: Don't call hvm_hypervisor_cpuid_leaf() for PV guests

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 14.11.16 at 12:01, <andrew.cooper3@xxxxxxxxxx> wrote:
> Luckily, hvm_hypervisor_cpuid_leaf() and vmx_hypervisor_cpuid_leaf() are safe
> to execute in the context of a PV guest, but HVM-specific feature flags
> shouldn't be visible to PV guests.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
albeit ...

> --- a/xen/arch/x86/traps.c
> +++ b/xen/arch/x86/traps.c
> @@ -928,6 +928,11 @@ int cpuid_hypervisor_leaves( uint32_t idx, uint32_t 
> sub_idx,
>          break;
>  
>      case 4:
> +        if ( !has_hvm_container_domain(currd) )
> +        {
> +            *eax = *ebx = *ecx = *edx = 0;
> +            break;
> +        }
>          hvm_hypervisor_cpuid_leaf(sub_idx, eax, ebx, ecx, edx);
>          break;

... this being the last leaf, wouldn't we better limit the number of
leaves (reported in leaf 0) to 3 for PV?

Jan


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