Re: [PATCH v2 1/4] KVM: nSVM: cancel KVM_REQ_GET_NESTED_STATE_PAGES on nested vmexit

[Paolo Bonzini]

On 07/01/21 18:51, Paolo Bonzini wrote:
> On 07/01/21 18:00, Sean Christopherson wrote:
> > Ugh, I assume this is due to one of the "premature" 
> > nested_ops->check_events()
> > calls that are necessitated by the event mess?  I'm guessing 
> > kvm_vcpu_running()
> > is the culprit?
> >
> > If my assumption is correct, this bug affects nVMX as well.
>
> Yes, though it may be latent.  For SVM it was until we started 
> allocating svm->nested on demand.
>
> > Rather than clear the request blindly on any nested VM-Exit, what
> > about something like the following?
>
> I think your patch is overkill, KVM_REQ_GET_NESTED_STATE_PAGES is only 
> set from KVM_SET_NESTED_STATE so it cannot happen while the VM runs.

... and when leaving SMM.  But in either case, there cannot be something 
else causing a nested vmexit before the request is set, because SMM does 
not support VMX operation.  So I still don't think that it justifies the 
extra code and indirection.

Paolo