qapi: introduce exit-on-error parameter for migrate-incoming

Now we do set MIGRATION_FAILED state, but don't give a chance to
orchestrator to query migration state and get the error.

Let's provide a possibility for QMP-based orchestrators to get an error
like with outgoing migration.

For hmp_migrate_incoming(), let's enable the new behavior: HMP is not
and ABI, it's mostly intended to use by developer and it makes sense
not to stop the process.

For x-exit-preconfig, let's keep the old behavior:
 - it's called from init(), so here we want to keep current behavior by
   default
 - it does exit on error by itself as well
So, if we want to change the behavior of x-exit-preconfig, it should be
another patch.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Acked-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>

migration/migration-hmp-cmds.c

@@ -466,7 +466,7 @@ void hmp_migrate_incoming(Monitor *mon, const QDict *qdict)
     }
     QAPI_LIST_PREPEND(caps, g_steal_pointer(&channel));
 
-    qmp_migrate_incoming(NULL, true, caps, &err);
+    qmp_migrate_incoming(NULL, true, caps, true, false, &err);
     qapi_free_MigrationChannelList(caps);
 
 end:

migration/migration.c

@@ -72,6 +72,8 @@
 #define NOTIFIER_ELEM_INIT(array, elem)    \
     [elem] = NOTIFIER_WITH_RETURN_LIST_INITIALIZER((array)[elem])
 
+#define INMIGRATE_DEFAULT_EXIT_ON_ERROR true
+
 static NotifierWithReturnList migration_state_notifiers[] = {
     NOTIFIER_ELEM_INIT(migration_state_notifiers, MIG_MODE_NORMAL),
     NOTIFIER_ELEM_INIT(migration_state_notifiers, MIG_MODE_CPR_REBOOT),
@@ -234,6 +236,8 @@ void migration_object_init(void)
     qemu_cond_init(&current_incoming->page_request_cond);
     current_incoming->page_requested = g_tree_new(page_request_addr_cmp);
 
+    current_incoming->exit_on_error = INMIGRATE_DEFAULT_EXIT_ON_ERROR;
+
     migration_object_check(current_migration, &error_fatal);
 
     blk_mig_init();
@@ -800,12 +804,14 @@ fail:
 
     migration_incoming_state_destroy();
 
-    WITH_QEMU_LOCK_GUARD(&s->error_mutex) {
-        error_report_err(s->error);
-        s->error = NULL;
-    }
+    if (mis->exit_on_error) {
+        WITH_QEMU_LOCK_GUARD(&s->error_mutex) {
+            error_report_err(s->error);
+            s->error = NULL;
+        }
 
-    exit(EXIT_FAILURE);
+        exit(EXIT_FAILURE);
+    }
 }
 
 /**
@@ -1314,6 +1320,15 @@ static void fill_destination_migration_info(MigrationInfo *info)
         break;
     }
     info->status = mis->state;
+
+    if (!info->error_desc) {
+        MigrationState *s = migrate_get_current();
+        QEMU_LOCK_GUARD(&s->error_mutex);
+
+        if (s->error) {
+            info->error_desc = g_strdup(error_get_pretty(s->error));
+        }
+    }
 }
 
 MigrationInfo *qmp_query_migrate(Error **errp)
@@ -1797,10 +1812,13 @@ void migrate_del_blocker(Error **reasonp)
 }
 
 void qmp_migrate_incoming(const char *uri, bool has_channels,
-                          MigrationChannelList *channels, Error **errp)
+                          MigrationChannelList *channels,
+                          bool has_exit_on_error, bool exit_on_error,
+                          Error **errp)
 {
     Error *local_err = NULL;
     static bool once = true;
+    MigrationIncomingState *mis = migration_incoming_get_current();
 
     if (!once) {
         error_setg(errp, "The incoming migration has already been started");
@@ -1815,6 +1833,9 @@ void qmp_migrate_incoming(const char *uri, bool has_channels,
         return;
     }
 
+    mis->exit_on_error =
+        has_exit_on_error ? exit_on_error : INMIGRATE_DEFAULT_EXIT_ON_ERROR;
+
     qemu_start_incoming_migration(uri, has_channels, channels, &local_err);
 
     if (local_err) {

migration/migration.h

@@ -227,6 +227,9 @@ struct MigrationIncomingState {
      * is needed as this field is updated serially.
      */
     unsigned int switchover_ack_pending_num;
+
+    /* Do exit on incoming migration failure */
+    bool exit_on_error;
 };
 
 MigrationIncomingState *migration_incoming_get_current(void);

qapi/migration.json

@@ -1837,6 +1837,10 @@
 # @channels: list of migration stream channels with each stream in the
 #     list connected to a destination interface endpoint.
 #
+# @exit-on-error: Exit on incoming migration failure.  Default true.
+#     When set to false, the failure triggers a MIGRATION event, and
+#     error details could be retrieved with query-migrate.  (since 9.1)
+#
 # Since: 2.3
 #
 # Notes:
@@ -1889,7 +1893,8 @@
 ##
 { 'command': 'migrate-incoming',
              'data': {'*uri': 'str',
-                      '*channels': [ 'MigrationChannel' ] } }
+                      '*channels': [ 'MigrationChannel' ],
+                      '*exit-on-error': 'bool' } }
 
 ##
 # @xen-save-devices-state:

system/vl.c

@@ -2723,7 +2723,8 @@ void qmp_x_exit_preconfig(Error **errp)
     if (incoming) {
         Error *local_err = NULL;
         if (strcmp(incoming, "defer") != 0) {
-            qmp_migrate_incoming(incoming, false, NULL, &local_err);
+            qmp_migrate_incoming(incoming, false, NULL, true, true,
+                                 &local_err);
             if (local_err) {
                 error_reportf_err(local_err, "-incoming %s: ", incoming);
                 exit(1);