Re: [PATCH] KVM: SVM: Add xsetbv intercept

Roedel, Joerg
2010-12-06T17:48:52Z

On Mon, Dec 06, 2010 at 11:10:46AM -0500, Avi Kivity wrote:
> On 12/03/2010 06:42 PM, Joerg Roedel wrote:
> > This patch implements the xsetbv intercept to the AMD part
> > of KVM. This makes AVX usable in a save way for the guest on
> > AVX capable AMD hardware.
> > The patch is tested by using AVX in the guest and host in
> > parallel and checking for data corruption. I also used the
> > KVM xsave unit-tests and they all pass.
> >
>
> That is really strange. You didn't need to do anything to get cpuid.avx
> recognized. So running an older kvm on newer hardware will happily
> expose avx even though it's not supported.
>
> We screwed up - we should have made cpuid.avx dependent on vendor support.

Hmm, right. The set_supported_cpuid arch-callback should basically
disable xsave on AMD for all KVM versions which do not handle the xsetbv
intercept.

Joerg

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