hyperv: synic: only setup ack notifier if there's a callback

There's no point setting up an sint ack notifier if no callback is
specified.
Signed-off-by: NRoman Kagan <rkagan@virtuozzo.com>
Message-Id: <20180921081836.29230-5-rkagan@virtuozzo.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

target/i386/hyperv.c

@@ -77,15 +77,14 @@ static void kvm_hv_sint_ack_handler(EventNotifier *notifier)
     HvSintRoute *sint_route = container_of(notifier, HvSintRoute,
                                            sint_ack_notifier);
     event_notifier_test_and_clear(notifier);
-    if (sint_route->sint_ack_clb) {
-        sint_route->sint_ack_clb(sint_route);
-    }
+    sint_route->sint_ack_clb(sint_route);
 }
 
 HvSintRoute *kvm_hv_sint_route_create(uint32_t vp_index, uint32_t sint,
                                       HvSintAckClb sint_ack_clb)
 {
     HvSintRoute *sint_route;
+    EventNotifier *ack_notifier;
     int r, gsi;
 
     sint_route = g_new0(HvSintRoute, 1);
@@ -94,13 +93,15 @@ HvSintRoute *kvm_hv_sint_route_create(uint32_t vp_index, uint32_t sint,
         goto err;
     }
 
-    r = event_notifier_init(&sint_route->sint_ack_notifier, false);
-    if (r) {
-        goto err_sint_set_notifier;
-    }
+    ack_notifier = sint_ack_clb ? &sint_route->sint_ack_notifier : NULL;
+    if (ack_notifier) {
+        r = event_notifier_init(ack_notifier, false);
+        if (r) {
+            goto err_sint_set_notifier;
+        }
 
-    event_notifier_set_handler(&sint_route->sint_ack_notifier,
-                               kvm_hv_sint_ack_handler);
+        event_notifier_set_handler(ack_notifier, kvm_hv_sint_ack_handler);
+    }
 
     gsi = kvm_irqchip_add_hv_sint_route(kvm_state, vp_index, sint);
     if (gsi < 0) {
@@ -109,7 +110,7 @@ HvSintRoute *kvm_hv_sint_route_create(uint32_t vp_index, uint32_t sint,
 
     r = kvm_irqchip_add_irqfd_notifier_gsi(kvm_state,
                                            &sint_route->sint_set_notifier,
-                                           &sint_route->sint_ack_notifier, gsi);
+                                           ack_notifier, gsi);
     if (r) {
         goto err_irqfd;
     }
@@ -123,8 +124,10 @@ HvSintRoute *kvm_hv_sint_route_create(uint32_t vp_index, uint32_t sint,
 err_irqfd:
     kvm_irqchip_release_virq(kvm_state, gsi);
 err_gsi:
-    event_notifier_set_handler(&sint_route->sint_ack_notifier, NULL);
-    event_notifier_cleanup(&sint_route->sint_ack_notifier);
+    if (ack_notifier) {
+        event_notifier_set_handler(ack_notifier, NULL);
+        event_notifier_cleanup(ack_notifier);
+    }
 err_sint_set_notifier:
     event_notifier_cleanup(&sint_route->sint_set_notifier);
 err:
@@ -139,8 +142,10 @@ void kvm_hv_sint_route_destroy(HvSintRoute *sint_route)
                                           &sint_route->sint_set_notifier,
                                           sint_route->gsi);
     kvm_irqchip_release_virq(kvm_state, sint_route->gsi);
-    event_notifier_set_handler(&sint_route->sint_ack_notifier, NULL);
-    event_notifier_cleanup(&sint_route->sint_ack_notifier);
+    if (sint_route->sint_ack_clb) {
+        event_notifier_set_handler(&sint_route->sint_ack_notifier, NULL);
+        event_notifier_cleanup(&sint_route->sint_ack_notifier);
+    }
     event_notifier_cleanup(&sint_route->sint_set_notifier);
     g_free(sint_route);
 }