migration: simplify notifiers

Pass the callback function to add_migration_state_change_notifier so
that migration can initialize the notifier on add and clear it on
delete, which simplifies the call sites.  Shorten the function names
so the extra arg can be added more legibly.  Hide the global notifier
list in a new function migration_call_notifiers, and make it externally
visible so future live update code can call it.

No functional change.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Tested-by: Michael Galaxy <mgalaxy@akamai.com>
Reviewed-by: Michael Galaxy <mgalaxy@akamai.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <1686148954-250144-1-git-send-email-steven.sistare@oracle.com>

hw/net/virtio-net.c

@@ -3624,8 +3624,8 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp)
         n->primary_listener.hide_device = failover_hide_primary_device;
         qatomic_set(&n->failover_primary_hidden, true);
         device_listener_register(&n->primary_listener);
-        n->migration_state.notify = virtio_net_migration_state_notifier;
-        add_migration_state_change_notifier(&n->migration_state);
+        migration_add_notifier(&n->migration_state,
+                               virtio_net_migration_state_notifier);
         n->host_features |= (1ULL << VIRTIO_NET_F_STANDBY);
     }
 
@@ -3788,7 +3788,7 @@ static void virtio_net_device_unrealize(DeviceState *dev)
     if (n->failover) {
         qobject_unref(n->primary_opts);
         device_listener_unregister(&n->primary_listener);
-        remove_migration_state_change_notifier(&n->migration_state);
+        migration_remove_notifier(&n->migration_state);
     } else {
         assert(n->primary_opts == NULL);
     }

hw/vfio/migration.c

@@ -872,8 +872,8 @@ static int vfio_migration_init(VFIODevice *vbasedev)
                      NULL;
     migration->vm_state = qdev_add_vm_change_state_handler_full(
         vbasedev->dev, vfio_vmstate_change, prepare_cb, vbasedev);
-    migration->migration_state.notify = vfio_migration_state_notifier;
-    add_migration_state_change_notifier(&migration->migration_state);
+    migration_add_notifier(&migration->migration_state,
+                           vfio_migration_state_notifier);
 
     return 0;
 }
@@ -882,7 +882,7 @@ static void vfio_migration_deinit(VFIODevice *vbasedev)
 {
     VFIOMigration *migration = vbasedev->migration;
 
-    remove_migration_state_change_notifier(&migration->migration_state);
+    migration_remove_notifier(&migration->migration_state);
     qemu_del_vm_change_state_handler(migration->vm_state);
     unregister_savevm(VMSTATE_IF(vbasedev->dev), "vfio", vbasedev);
     vfio_migration_free(vbasedev);

include/migration/misc.h

@@ -60,8 +60,10 @@ void migration_object_init(void);
 void migration_shutdown(void);
 bool migration_is_idle(void);
 bool migration_is_active(MigrationState *);
-void add_migration_state_change_notifier(Notifier *notify);
-void remove_migration_state_change_notifier(Notifier *notify);
+void migration_add_notifier(Notifier *notify,
+                            void (*func)(Notifier *notifier, void *data));
+void migration_remove_notifier(Notifier *notify);
+void migration_call_notifiers(MigrationState *s);
 bool migration_in_setup(MigrationState *);
 bool migration_has_finished(MigrationState *);
 bool migration_has_failed(MigrationState *);

migration/migration.c

@@ -1207,7 +1207,7 @@ static void migrate_fd_cleanup(MigrationState *s)
         /* It is used on info migrate.  We can't free it */
         error_report_err(error_copy(s->error));
     }
-    notifier_list_notify(&migration_state_notifiers, s);
+    migration_call_notifiers(s);
     block_cleanup_parameters();
     yank_unregister_instance(MIGRATION_YANK_INSTANCE);
 }
@@ -1311,14 +1311,24 @@ static void migrate_fd_cancel(MigrationState *s)
     }
 }
 
-void add_migration_state_change_notifier(Notifier *notify)
+void migration_add_notifier(Notifier *notify,
+                            void (*func)(Notifier *notifier, void *data))
 {
+    notify->notify = func;
     notifier_list_add(&migration_state_notifiers, notify);
 }
 
-void remove_migration_state_change_notifier(Notifier *notify)
+void migration_remove_notifier(Notifier *notify)
+{
+    if (notify->notify) {
+        notifier_remove(notify);
+        notify->notify = NULL;
+    }
+}
+
+void migration_call_notifiers(MigrationState *s)
 {
-    notifier_remove(notify);
+    notifier_list_notify(&migration_state_notifiers, s);
 }
 
 bool migration_in_setup(MigrationState *s)
@@ -2233,7 +2243,7 @@ static int postcopy_start(MigrationState *ms, Error **errp)
      * spice needs to trigger a transition now
      */
     ms->postcopy_after_devices = true;
-    notifier_list_notify(&migration_state_notifiers, ms);
+    migration_call_notifiers(ms);
 
     ms->downtime =  qemu_clock_get_ms(QEMU_CLOCK_REALTIME) - time_at_stop;
 
@@ -3313,7 +3323,7 @@ void migrate_fd_connect(MigrationState *s, Error *error_in)
         rate_limit = migrate_max_bandwidth();
 
         /* Notify before starting migration thread */
-        notifier_list_notify(&migration_state_notifiers, s);
+        migration_call_notifiers(s);
     }
 
     migration_rate_set(rate_limit);

net/vhost-vdpa.c

@@ -339,7 +339,8 @@ static void vhost_vdpa_net_data_start_first(VhostVDPAState *s)
 {
     struct vhost_vdpa *v = &s->vhost_vdpa;
 
-    add_migration_state_change_notifier(&s->migration_state);
+    migration_add_notifier(&s->migration_state,
+                           vdpa_net_migration_state_notifier);
     if (v->shadow_vqs_enabled) {
         v->iova_tree = vhost_iova_tree_new(v->iova_range.first,
                                            v->iova_range.last);
@@ -399,7 +400,7 @@ static void vhost_vdpa_net_client_stop(NetClientState *nc)
     assert(nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA);
 
     if (s->vhost_vdpa.index == 0) {
-        remove_migration_state_change_notifier(&s->migration_state);
+        migration_remove_notifier(&s->migration_state);
     }
 
     dev = s->vhost_vdpa.dev;
@@ -1456,7 +1457,7 @@ static NetClientState *net_vhost_vdpa_init(NetClientState *peer,
     s->vhost_vdpa.device_fd = vdpa_device_fd;
     s->vhost_vdpa.index = queue_pair_index;
     s->always_svq = svq;
-    s->migration_state.notify = vdpa_net_migration_state_notifier;
+    s->migration_state.notify = NULL;
     s->vhost_vdpa.shadow_vqs_enabled = svq;
     s->vhost_vdpa.iova_range = iova_range;
     s->vhost_vdpa.shadow_data = svq;

ui/spice-core.c

@@ -821,8 +821,7 @@ static void qemu_spice_init(void)
     };
     using_spice = 1;
 
-    migration_state.notify = migration_state_notifier;
-    add_migration_state_change_notifier(&migration_state);
+    migration_add_notifier(&migration_state, migration_state_notifier);
     spice_migrate.base.sif = &migrate_interface.base;
     qemu_spice.add_interface(&spice_migrate.base);