On 04/05/20 11:13, Maxim Levitsky wrote: > On Mon, 2020-05-04 at 15:46 +0700, Suravee Suthikulpanit wrote: >> Paolo / Maxim, >> >> On 5/2/20 11:42 PM, 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? >> >> Instead, as an alternative to remove the WARN_ON(), would it be better to just explicitly >> calling kvm_vcpu_update_apicv(vcpu) to update the apicv_active flag right after >> kvm_request_apicv_update()? >> > This should work IMHO, other that the fact kvm_vcpu_update_apicv will be called again, > when this vcpu is entered since the KVM_REQ_APICV_UPDATE will still be pending on it. > It shoudn't be a problem, and we can even add a check to do nothing when it is called > while avic is already in target enable state. I thought about that but I think it's a bit confusing. If we want to keep the WARN_ON, Maxim can add an equivalent one to svm_vcpu_run, which is even better because the invariant is clearer. WARN_ON((vmcb->control.int_ctl & (AVIC_ENABLE_MASK | V_IRQ_MASK)) == (AVIC_ENABLE_MASK | V_IRQ_MASK)); Paolo
