Re: [PATCH v2 1/2] KVM: SVM: Move asid to vcpu_svm

[Paolo Bonzini]

On 29/11/20 10:41, Ashish Kalra wrote:
> From: Ashish Kalra <ashish.kalra@xxxxxxx>
>
> This patch breaks SEV guests.
>
> The patch stores current ASID in struct vcpu_svm and only moves it to VMCB in
> svm_vcpu_run(), but by doing so, the ASID allocated for SEV guests and setup
> in vmcb->control.asid by pre_sev_run() gets over-written by this ASID
> stored in struct vcpu_svm and hence, VMRUN fails as SEV guest is bound/activated
> on a different ASID then the one overwritten in vmcb->control.asid at VMRUN.
>
> For example, asid#1 was activated for SEV guest and then vmcb->control.asid is
> overwritten with asid#0 (svm->asid) as part of this patch in svm_vcpu_run() and
> hence VMRUN fails.

Thanks Ashish, I've sent a patch to fix it.

Would it be possible to add a minimal SEV test to 
tools/testing/selftests/kvm?  It doesn't have to do full attestation 
etc., if you can just write an "out" instruction using SEV_DBG_ENCRYPT 
and check that you can run it that's enough.

Paolo