Re: [PATCH v2 1/5] KVM: nSVM: deal with L1 hypervisor that intercepts interrupts but lets L2 control EFLAGS.IF

[Paolo Bonzini]

On 12/13/21 14:07, Maxim Levitsky wrote:
> > Right, another case is when CLGI is not trapped and the guest therefore
> > runs with GIF=0.  I think that means that a similar change has to be
> > done in all the *_allowed functions.
>
> I think that SVM sets real GIF to 1 on VMentry regardless if it is trapped or not.

Yes, the issue is only when CLGI is not trapped (and vGIF is disabled).

> However if not trapped, and neither EFLAGS.IF is trapped, one could enter a guest
> that has EFLAGS.IF == 0, then the guest could disable GIF, enable EFLAGS.IF,
> and then enable GIF, but then GIF enablement should trigger out interrupt window
> VINTR as well.

While GIF=0 you have svm_nmi_blocked returning true and svm_nmi_allowed 
returning -EBUSY; that's wrong isn't it?

Paolo