KVM: nVMX: don't clear mtf_pending when nested events are blocked

If nested events are blocked, don't clear the mtf_pending flag to avoid
missing later delivery of the MTF VM-exit.

Fixes: 5ef8acb ("KVM: nVMX: Emulate MTF when performing instruction emulation")
Signed-off-by: Oliver Upton <oupton@google.com>
Message-Id: <20200406201237.178725-1-oupton@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/nested.c

@@ -3645,7 +3645,8 @@ static int vmx_check_nested_events(struct kvm_vcpu *vcpu)
 	 * Clear the MTF state. If a higher priority VM-exit is delivered first,
 	 * this state is discarded.
 	 */
-	vmx->nested.mtf_pending = false;
+	if (!block_nested_events)
+		vmx->nested.mtf_pending = false;
 
 	if (lapic_in_kernel(vcpu) &&
 		test_bit(KVM_APIC_INIT, &apic->pending_events)) {