WHPX improve interrupt notification registration

Improves the usage of the InterruptNotification registration by skipping the
additional call to WHvSetVirtualProcessorRegisters if we have already
registered for the window exit.
Signed-off-by: NJustin Terry (VM) <juterry@microsoft.com>
Message-Id: <1519665216-1078-9-git-send-email-juterry@microsoft.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NJustin Terry (VM) via Qemu-devel <qemu-devel@nongnu.org>

target/i386/whpx-all.c

@@ -756,12 +756,11 @@ static void whpx_vcpu_pre_run(CPUState *cpu)
     }
 
     /* Update the state of the interrupt delivery notification */
-    if (cpu->interrupt_request & CPU_INTERRUPT_HARD) {
+    if (!vcpu->window_registered &&
+        cpu->interrupt_request & CPU_INTERRUPT_HARD) {
         reg_values[reg_count].DeliverabilityNotifications.InterruptNotification
             = 1;
-        if (vcpu->window_registered != 1) {
-            vcpu->window_registered = 1;
-        }
+        vcpu->window_registered = 1;
         reg_names[reg_count] = WHvX64RegisterDeliverabilityNotifications;
         reg_count += 1;
     }