Re: [Xen-devel] [PATCH v2] x86/hvm: Extend HVM cpuid leaf with vcpu id

[Matt Wilson <msw@xxxxxxxxx>]

On Thu, Nov 06, 2014 at 03:26:24PM +0000, Paul Durrant wrote:
> To perform certain hypercalls HVM guests need to use Xen's idea of
> vcpu id, which may well not match the guest OS idea of CPU id.
> This patch adds vcpu id to the HVM cpuid leaf allowing the guest
> to build a mapping.

One more tangent on this, since this is partially considered in a
Windows context. Why not use the existing Viridian virtual processor
index MSR for this, since that would work on Xen today.

xen/arch/x86/hvm/viridian.c:
> #define VIRIDIAN_MSR_VP_INDEX                   0x40000002
> ...
>     case VIRIDIAN_MSR_VP_INDEX:
>        perfc_incr(mshv_rdmsr_vp_index);
>        *val = v->vcpu_id;
>        break;

--msw

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