Re: AVIC related warning in enable_irq_window

[Suravee Suthikulpanit]

Maxim / Paolo,

On 5/2/20 11:43 PM, Maxim Levitsky wrote:
> On Sat, 2020-05-02 at 18:42 +0200, Paolo Bonzini wrote:
> > On 02/05/20 15:58, Maxim Levitsky wrote:
> > > The AVIC is disabled by svm_toggle_avic_for_irq_window, which calls
> > > kvm_request_apicv_update, which broadcasts the KVM_REQ_APICV_UPDATE vcpu request,
> > > however it doesn't broadcast it to CPU on which now we are running, which seems OK,
> > > because the code that handles that broadcast runs on each VCPU entry, thus
> > > when this CPU will enter guest mode it will notice and disable the AVIC.
> > >
> > > However later in svm_enable_vintr, there is test 'WARN_ON(kvm_vcpu_apicv_active(&svm->vcpu));'
> > > which is still true on current CPU because of the above.
> >
> > Good point!  We can just remove the WARN_ON I think.  Can you send a patch?
> >
> > svm_set_vintr also has a rather silly
> >
> > static void svm_set_vintr(struct vcpu_svm *svm)
> > {
> >         set_intercept(svm, INTERCEPT_VINTR);
> >         if (is_intercept(svm, INTERCEPT_VINTR))
> >                 svm_enable_vintr(svm);
> > }
> >
> > so I'm thinking of just inlining svm_enable_vintr and renaming
> > svm_{set,clear}_vintr to svm_{enable,disable}_vintr_window.  Would you
> > like to send two patches for this, the first to remove the WARN_ON and
> > the second to do the cleanup?
>
> Absolutely! I will send a patch very soon.

I have been debugging this and I have a patch that is supposed to fix this
(instead of removing the WARN ON). Please do not remove the warn on just yet.

Thanks,
Suravee