Revert "virtio: postpone the execution of event_notifier_cleanup function"

This reverts commit 4fe6d78b as it is
reported to break cleanup and migration.

Cc: Gal Hammer <ghammer@redhat.com>
Cc: Sitong Liu <siliu@redhat.com>
Cc: Xiaoling Gao <xiagao@redhat.com>
Suggested-by: NGreg Kurz <groug@kaod.org>
Suggested-by: NPaolo Bonzini <pbonzini@redhat.com>
Reported-by: NJose Ricardo Ziviani <joserz@linux.vnet.ibm.com>
Reported-by: NDaniel Henrique Barboza <danielhb@linux.vnet.ibm.com>

accel/kvm/kvm-all.c

@@ -812,10 +812,6 @@ static void kvm_mem_ioeventfd_del(MemoryListener *listener,
     if (r < 0) {
         abort();
     }
-
-    if (e->cleanup) {
-        e->cleanup(e);
-    }
 }
 
 static void kvm_io_ioeventfd_add(MemoryListener *listener,

hw/virtio/virtio-bus.c

@@ -256,15 +256,6 @@ bool virtio_bus_ioeventfd_enabled(VirtioBusState *bus)
     return k->ioeventfd_assign && k->ioeventfd_enabled(proxy);
 }
 
-static void virtio_bus_cleanup_event_notifier(EventNotifier *notifier)
-{
-    /* Test and clear notifier after disabling event,
-     * in case poll callback didn't have time to run.
-     */
-    virtio_queue_host_notifier_read(notifier);
-    event_notifier_cleanup(notifier);
-}
-
 /*
  * This function switches ioeventfd on/off in the device.
  * The caller must set or clear the handlers for the EventNotifier.
@@ -292,13 +283,19 @@ int virtio_bus_set_host_notifier(VirtioBusState *bus, int n, bool assign)
         r = k->ioeventfd_assign(proxy, notifier, n, true);
         if (r < 0) {
             error_report("%s: unable to assign ioeventfd: %d", __func__, r);
-            virtio_bus_cleanup_event_notifier(notifier);
+            goto cleanup_event_notifier;
         }
+        return 0;
     } else {
-        notifier->cleanup = virtio_bus_cleanup_event_notifier;
         k->ioeventfd_assign(proxy, notifier, n, false);
     }
 
+cleanup_event_notifier:
+    /* Test and clear notifier after disabling event,
+     * in case poll callback didn't have time to run.
+     */
+    virtio_queue_host_notifier_read(notifier);
+    event_notifier_cleanup(notifier);
     return r;
 }