KVM: x86: lapic: don't touch irr_pending in kvm_apic_update_apicv when inhibiting it

kvm_apic_update_apicv is called when AVIC is still active, thus IRR bits
can be set by the CPU after it is called, and don't cause the irr_pending
to be set to true.

Also logic in avic_kick_target_vcpu doesn't expect a race with this
function so to make it simple, just keep irr_pending set to true and
let the next interrupt injection to the guest clear it.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20220207155447.840194-9-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index d7e6fde82d254408fe3b208eb5631d1c718c71a7..9322e6340a742b88f346decab60f46f65d7e3b6b 100644 (file)
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2306,7 +2306,12 @@ void kvm_apic_update_apicv(struct kvm_vcpu *vcpu)
                apic->irr_pending = true;
                apic->isr_count = 1;
        } else {
-               apic->irr_pending = (apic_search_irr(apic) != -1);
+               /*
+                * Don't clear irr_pending, searching the IRR can race with
+                * updates from the CPU as APICv is still active from hardware's
+                * perspective.  The flag will be cleared as appropriate when
+                * KVM injects the interrupt.
+                */
                apic->isr_count = count_vectors(apic->regs + APIC_ISR);
        }
 }