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SubjectRE: [PATCH] KVM: x86: emulate wait-for-SIPI and SIPI-VMExit
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> There is a problem in this patch, in that this change is incorrect:
>
> >
> > @@ -2847,7 +2847,8 @@ void kvm_apic_accept_events(struct kvm_vcpu
> *vcpu)
> > */
> > if (kvm_vcpu_latch_init(vcpu)) {
> > WARN_ON_ONCE(vcpu->arch.mp_state ==
> KVM_MP_STATE_INIT_RECEIVED);
> > - if (test_bit(KVM_APIC_SIPI, &apic->pending_events))
> > + if (test_bit(KVM_APIC_SIPI, &apic->pending_events) &&
> > + !is_guest_mode(vcpu))
> > clear_bit(KVM_APIC_SIPI, &apic->pending_events);
> > return;
> > }
>
> Here you're not trying to process a latched INIT; you just want to delay the
> processing of the SIPI until check_nested_events.
>
> The change does have a correct part in it. In particular,
> vmx_apic_init_signal_blocked should have been
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index
> 47b8357b9751..64339121a4f0 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7558,7 +7558,7 @@ static void enable_smi_window(struct kvm_vcpu
> *vcpu)
>
> static bool vmx_apic_init_signal_blocked(struct kvm_vcpu *vcpu)
> {
> - return to_vmx(vcpu)->nested.vmxon;
> + return to_vmx(vcpu)->nested.vmxon && !is_guest_mode(vcpu);
> }
>
> static void vmx_migrate_timers(struct kvm_vcpu *vcpu)
>
> to only latch INIT signals in root mode. However, SIPI must be cleared
> unconditionally on SVM; the "!is_guest_mode" test in that case is incorrect.
>
> The right way to do it is to call check_nested_events from
> kvm_apic_accept_events. This will cause an INIT or SIPI vmexit, as required.
> There is some extra complication to read pending_events
> *before* kvm_apic_accept_events and not steal from the guest any INIT or SIPI
> that is sent after kvm_apic_accept_events returns.
>
> Thanks to your test case, I will test a patch and send it.
>
Thanks very much, Paolo.
BTW, I noticed another issue in sync_vmcs02_to_vmcs12():
vmcs12->guest_activity_state is not set properly when mp_state is INIT_RECEIVED.
I will correct it and send v2 of Patch 2/2.
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