KVM: x86: Don't inhibit APICv/AVIC on xAPIC ID "change" if APIC is di…

…sabled

commit a58a66a upstream.

Don't inhibit APICv/AVIC due to an xAPIC ID mismatch if the APIC is
hardware disabled.  The ID cannot be consumed while the APIC is disabled,
and the ID is guaranteed to be set back to the vcpu_id when the APIC is
hardware enabled (architectural behavior correctly emulated by KVM).

Fixes: 3743c2f ("KVM: x86: inhibit APICv/AVIC on changes to APIC ID or APIC base")
Cc: stable@vger.kernel.org
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20230106011306.85230-6-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/x86/kvm/lapic.c

@@ -2072,6 +2072,9 @@ static void kvm_lapic_xapic_id_updated(struct kvm_lapic *apic)
 {
 	struct kvm *kvm = apic->vcpu->kvm;
 
+	if (!kvm_apic_hw_enabled(apic))
+		return;
+
 	if (KVM_BUG_ON(apic_x2apic_mode(apic), kvm))
 		return;