migration: MigrationEvent for notifiers

Passing MigrationState to notifiers is unsound because they could access
unstable migration state internals or even modify the state.  Instead, pass
the minimal info needed in a new MigrationEvent struct, which could be
extended in the future if needed.

Suggested-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/1708622920-68779-5-git-send-email-steven.sistare@oracle.com
Signed-off-by: Peter Xu <peterx@redhat.com>

hw/net/virtio-net.c

@@ -3504,7 +3504,7 @@ out:
     return !err;
 }
 
-static void virtio_net_handle_migration_primary(VirtIONet *n, MigrationState *s)
+static void virtio_net_handle_migration_primary(VirtIONet *n, MigrationEvent *e)
 {
     bool should_be_hidden;
     Error *err = NULL;
@@ -3516,7 +3516,7 @@ static void virtio_net_handle_migration_primary(VirtIONet *n, MigrationState *s)
 
     should_be_hidden = qatomic_read(&n->failover_primary_hidden);
 
-    if (migration_in_setup(s) && !should_be_hidden) {
+    if (e->type == MIG_EVENT_PRECOPY_SETUP && !should_be_hidden) {
         if (failover_unplug_primary(n, dev)) {
             vmstate_unregister(VMSTATE_IF(dev), qdev_get_vmsd(dev), dev);
             qapi_event_send_unplug_primary(dev->id);
@@ -3524,7 +3524,7 @@ static void virtio_net_handle_migration_primary(VirtIONet *n, MigrationState *s)
         } else {
             warn_report("couldn't unplug primary device");
         }
-    } else if (migration_has_failed(s)) {
+    } else if (e->type == MIG_EVENT_PRECOPY_FAILED) {
         /* We already unplugged the device let's plug it back */
         if (!failover_replug_primary(n, dev, &err)) {
             if (err) {
@@ -3537,9 +3537,10 @@ static void virtio_net_handle_migration_primary(VirtIONet *n, MigrationState *s)
 static int virtio_net_migration_state_notifier(NotifierWithReturn *notifier,
                                                void *data, Error **errp)
 {
-    MigrationState *s = data;
+    MigrationEvent *e = data;
+
     VirtIONet *n = container_of(notifier, VirtIONet, migration_state);
-    virtio_net_handle_migration_primary(n, s);
+    virtio_net_handle_migration_primary(n, e);
     return 0;
 }
 

hw/vfio/migration.c

@@ -757,18 +757,14 @@ static void vfio_vmstate_change(void *opaque, bool running, RunState state)
 static int vfio_migration_state_notifier(NotifierWithReturn *notifier,
                                          void *data, Error **errp)
 {
-    MigrationState *s = data;
+    MigrationEvent *e = data;
     VFIOMigration *migration = container_of(notifier, VFIOMigration,
                                             migration_state);
     VFIODevice *vbasedev = migration->vbasedev;
 
-    trace_vfio_migration_state_notifier(vbasedev->name,
+    trace_vfio_migration_state_notifier(vbasedev->name, e->type);
-                                        MigrationStatus_str(s->state));
 
-    switch (s->state) {
+    if (e->type == MIG_EVENT_PRECOPY_FAILED) {
-    case MIGRATION_STATUS_CANCELLING:
-    case MIGRATION_STATUS_CANCELLED:
-    case MIGRATION_STATUS_FAILED:
         vfio_migration_set_state_or_reset(vbasedev, VFIO_DEVICE_STATE_RUNNING);
     }
     return 0;

hw/vfio/trace-events

@@ -153,7 +153,7 @@ vfio_load_state(const char *name, uint64_t data) " (%s) data 0x%"PRIx64
 vfio_load_state_device_data(const char *name, uint64_t data_size, int ret) " (%s) size 0x%"PRIx64" ret %d"
 vfio_migration_realize(const char *name) " (%s)"
 vfio_migration_set_state(const char *name, const char *state) " (%s) state %s"
-vfio_migration_state_notifier(const char *name, const char *state) " (%s) state %s"
+vfio_migration_state_notifier(const char *name, int state) " (%s) state %d"
 vfio_save_block(const char *name, int data_size) " (%s) data_size %d"
 vfio_save_cleanup(const char *name) " (%s)"
 vfio_save_complete_precopy(const char *name, int ret) " (%s) ret %d"

include/migration/misc.h

@@ -60,10 +60,31 @@ void migration_object_init(void);
 void migration_shutdown(void);
 bool migration_is_idle(void);
 bool migration_is_active(MigrationState *);
+
+typedef enum MigrationEventType {
+    MIG_EVENT_PRECOPY_SETUP,
+    MIG_EVENT_PRECOPY_DONE,
+    MIG_EVENT_PRECOPY_FAILED,
+    MIG_EVENT_MAX
+} MigrationEventType;
+
+typedef struct MigrationEvent {
+    MigrationEventType type;
+} MigrationEvent;
+
+/*
+ * Register the notifier @notify to be called when a migration event occurs
+ * for MIG_MODE_NORMAL, as specified by the MigrationEvent passed to @func.
+ * Notifiers may receive events in any of the following orders:
+ *    - MIG_EVENT_PRECOPY_SETUP -> MIG_EVENT_PRECOPY_DONE
+ *    - MIG_EVENT_PRECOPY_SETUP -> MIG_EVENT_PRECOPY_FAILED
+ *    - MIG_EVENT_PRECOPY_FAILED
+ */
 void migration_add_notifier(NotifierWithReturn *notify,
                             NotifierWithReturnFunc func);
+
 void migration_remove_notifier(NotifierWithReturn *notify);
-void migration_call_notifiers(MigrationState *s);
+void migration_call_notifiers(MigrationState *s, MigrationEventType type);
 bool migration_in_setup(MigrationState *);
 bool migration_has_finished(MigrationState *);
 bool migration_has_failed(MigrationState *);

migration/migration.c

@@ -1319,6 +1319,8 @@ void migrate_set_state(int *state, int old_state, int new_state)
 
 static void migrate_fd_cleanup(MigrationState *s)
 {
+    MigrationEventType type;
+
     g_free(s->hostname);
     s->hostname = NULL;
     json_writer_free(s->vmdesc);
@@ -1367,7 +1369,9 @@ 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));
     }
-    migration_call_notifiers(s);
+    type = migration_has_failed(s) ? MIG_EVENT_PRECOPY_FAILED :
+                                     MIG_EVENT_PRECOPY_DONE;
+    migration_call_notifiers(s, type);
     block_cleanup_parameters();
     yank_unregister_instance(MIGRATION_YANK_INSTANCE);
 }
@@ -1474,9 +1478,12 @@ void migration_remove_notifier(NotifierWithReturn *notify)
     }
 }
 
-void migration_call_notifiers(MigrationState *s)
+void migration_call_notifiers(MigrationState *s, MigrationEventType type)
 {
-    notifier_with_return_list_notify(&migration_state_notifiers, s, 0);
+    MigrationEvent e;
+
+    e.type = type;
+    notifier_with_return_list_notify(&migration_state_notifiers, &e, 0);
 }
 
 bool migration_in_setup(MigrationState *s)
@@ -2537,7 +2544,7 @@ static int postcopy_start(MigrationState *ms, Error **errp)
      * spice needs to trigger a transition now
      */
     ms->postcopy_after_devices = true;
-    migration_call_notifiers(ms);
+    migration_call_notifiers(ms, MIG_EVENT_PRECOPY_DONE);
 
     migration_downtime_end(ms);
 
@@ -3601,7 +3608,7 @@ void migrate_fd_connect(MigrationState *s, Error *error_in)
         rate_limit = migrate_max_bandwidth();
 
         /* Notify before starting migration thread */
-        migration_call_notifiers(s);
+        migration_call_notifiers(s, MIG_EVENT_PRECOPY_SETUP);
     }
 
     migration_rate_set(rate_limit);

net/vhost-vdpa.c

@@ -325,13 +325,13 @@ static void vhost_vdpa_net_log_global_enable(VhostVDPAState *s, bool enable)
 static int vdpa_net_migration_state_notifier(NotifierWithReturn *notifier,
                                              void *data, Error **errp)
 {
-    MigrationState *migration = data;
+    MigrationEvent *e = data;
     VhostVDPAState *s = container_of(notifier, VhostVDPAState,
                                      migration_state);
 
-    if (migration_in_setup(migration)) {
+    if (e->type == MIG_EVENT_PRECOPY_SETUP) {
         vhost_vdpa_net_log_global_enable(s, true);
-    } else if (migration_has_failed(migration)) {
+    } else if (e->type == MIG_EVENT_PRECOPY_FAILED) {
         vhost_vdpa_net_log_global_enable(s, false);
     }
     return 0;

ui/spice-core.c

@@ -571,19 +571,18 @@ static SpiceInfo *qmp_query_spice_real(Error **errp)
 static int migration_state_notifier(NotifierWithReturn *notifier,
                                     void *data, Error **errp)
 {
-    MigrationState *s = data;
+    MigrationEvent *e = data;
 
     if (!spice_have_target_host) {
         return 0;
     }
 
-    if (migration_in_setup(s)) {
+    if (e->type == MIG_EVENT_PRECOPY_SETUP) {
         spice_server_migrate_start(spice_server);
-    } else if (migration_has_finished(s) ||
+    } else if (e->type == MIG_EVENT_PRECOPY_DONE) {
-               migration_in_postcopy_after_devices(s)) {
         spice_server_migrate_end(spice_server, true);
         spice_have_target_host = false;
-    } else if (migration_has_failed(s)) {
+    } else if (e->type == MIG_EVENT_PRECOPY_FAILED) {
         spice_server_migrate_end(spice_server, false);
         spice_have_target_host = false;
     }