migration: Handle error in the early async paths

Simplify migration_channel_connect() and migration_connect() to not
take an error as input. Move the error handling into the paths that
generate the error.

To achieve this, call migration_connect_error_propagate() from
socket.c and tls.c, which are the async paths.

For the sync paths, the handling is done as normal by returning all
the way to qmp_migrate_finish(), except that now the sync paths don't
pass the error forward into migration_connect() anymore.

Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Prasad Pandit <pjp@fedoraproject.org>
Link: https://lore.kernel.org/qemu-devel/20260123141656.6765-13-farosas@suse.de
Signed-off-by: Fabiano Rosas <farosas@suse.de>

migration/channel.c

@@ -60,28 +60,26 @@ void migration_channel_process_incoming(QIOChannel *ioc)
  *
  * @s: Current migration state
  * @ioc: Channel to which we are connecting
- * @error: Error indicating failure to connect, free'd here
  */
-void migration_channel_connect(MigrationState *s,
-                               QIOChannel *ioc,
-                               Error *error)
+void migration_channel_connect(MigrationState *s, QIOChannel *ioc)
 {
-    trace_migration_set_outgoing_channel(
-        ioc, object_get_typename(OBJECT(ioc)), error);
+    trace_migration_set_outgoing_channel(ioc, object_get_typename(OBJECT(ioc)));
 
-    if (!error) {
     if (migrate_channel_requires_tls_upgrade(ioc)) {
-            migration_tls_channel_connect(s, ioc, &error);
+        Error *local_err = NULL;
 
-            if (!error) {
-                /* tls_channel_connect will call back to this
-                 * function after the TLS handshake,
-                 * so we mustn't call migration_connect until then
-                 */
+        migration_tls_channel_connect(s, ioc, &local_err);
+        if (local_err) {
+            migration_connect_error_propagate(s, local_err);
+        }
 
+        /*
+         * async: the above will call back to this function after
+         * the TLS handshake is successfully completed.
+         */
         return;
     }
-        } else {
+
     QEMUFile *f = qemu_file_new_output(ioc);
 
     migration_ioc_register_yank(ioc);
@@ -89,9 +87,8 @@ void migration_channel_connect(MigrationState *s,
     qemu_mutex_lock(&s->qemu_file_lock);
     s->to_dst_file = f;
     qemu_mutex_unlock(&s->qemu_file_lock);
-        }
-    }
-    migration_connect(s, error);
+
+    migration_connect(s);
 }
 
 

migration/channel.h

@@ -20,9 +20,7 @@
 
 void migration_channel_process_incoming(QIOChannel *ioc);
 
-void migration_channel_connect(MigrationState *s,
-                               QIOChannel *ioc,
-                               Error *error_in);
+void migration_channel_connect(MigrationState *s, QIOChannel *ioc);
 
 int migration_channel_read_peek(QIOChannel *ioc,
                                 const char *buf,

migration/exec.c

@@ -55,7 +55,7 @@ void exec_start_outgoing_migration(MigrationState *s, strList *command,
     }
 
     qio_channel_set_name(ioc, "migration-exec-outgoing");
-    migration_channel_connect(s, ioc, NULL);
+    migration_channel_connect(s, ioc);
     object_unref(OBJECT(ioc));
 }
 

migration/fd.c

@@ -72,7 +72,7 @@ void fd_start_outgoing_migration(MigrationState *s, const char *fdname, Error **
     }
 
     qio_channel_set_name(ioc, "migration-fd-outgoing");
-    migration_channel_connect(s, ioc, NULL);
+    migration_channel_connect(s, ioc);
     object_unref(OBJECT(ioc));
 }
 

migration/file.c

@@ -122,7 +122,7 @@ void file_start_outgoing_migration(MigrationState *s,
         return;
     }
     qio_channel_set_name(ioc, "migration-file-outgoing");
-    migration_channel_connect(s, ioc, NULL);
+    migration_channel_connect(s, ioc);
 }
 
 static gboolean file_accept_incoming_migration(QIOChannel *ioc,

migration/migration.c

@@ -1569,7 +1569,7 @@ static void migrate_error_free(MigrationState *s)
     s->error = NULL;
 }
 
-static void migration_connect_error_propagate(MigrationState *s, Error *error)
+void migration_connect_error_propagate(MigrationState *s, Error *error)
 {
     MigrationStatus current = s->state;
     MigrationStatus next = MIGRATION_STATUS_NONE;
@@ -4020,7 +4020,7 @@ fail_setup:
     return NULL;
 }
 
-void migration_connect(MigrationState *s, Error *error_in)
+void migration_connect(MigrationState *s)
 {
     Error *local_err = NULL;
     uint64_t rate_limit;
@@ -4028,13 +4028,6 @@ void migration_connect(MigrationState *s, Error *error_in)
     int ret;
 
     s->expected_downtime = migrate_downtime_limit();
-    if (error_in) {
-        migration_connect_error_propagate(s, error_in);
-        if (s->error) {
-            error_report_err(error_copy(s->error));
-        }
-        return;
-    }
 
     if (resume) {
         /* This is a resumed migration */

migration/migration.h

@@ -533,10 +533,11 @@ void migration_incoming_process(void);
 
 bool  migration_has_all_channels(void);
 
+void migration_connect_error_propagate(MigrationState *s, Error *error);
 void migrate_error_propagate(MigrationState *s, Error *error);
 bool migrate_has_error(MigrationState *s);
 
-void migration_connect(MigrationState *s, Error *error_in);
+void migration_connect(MigrationState *s);
 
 int migration_call_notifiers(MigrationEventType type, Error **errp);
 

migration/rdma.c

@@ -3996,7 +3996,7 @@ void rdma_start_outgoing_migration(void *opaque,
 
     s->to_dst_file = rdma_new_output(rdma);
     s->rdma_migration = true;
-    migration_connect(s, NULL);
+    migration_connect(s);
     return;
 return_path_err:
     qemu_rdma_cleanup(rdma);

migration/socket.c

@@ -59,24 +59,25 @@ static void socket_outgoing_migration(QIOTask *task,
                                       gpointer opaque)
 {
     struct SocketConnectData *data = opaque;
-    QIOChannel *sioc = QIO_CHANNEL(qio_task_get_source(task));
+    g_autoptr(QIOChannel) sioc = QIO_CHANNEL(qio_task_get_source(task));
     Error *err = NULL;
 
     if (qio_task_propagate_error(task, &err)) {
-        trace_migration_socket_outgoing_error(error_get_pretty(err));
-           goto out;
+        goto fail;
     }
 
-    trace_migration_socket_outgoing_connected();
-
     if (migrate_zero_copy_send() &&
         !qio_channel_has_feature(sioc, QIO_CHANNEL_FEATURE_WRITE_ZERO_COPY)) {
         error_setg(&err, "Zero copy send feature not detected in host kernel");
+        goto fail;
     }
 
-out:
-    migration_channel_connect(data->s, sioc, err);
-    object_unref(OBJECT(sioc));
+    trace_migration_socket_outgoing_connected();
+    migration_channel_connect(data->s, sioc);
+    return;
+fail:
+    trace_migration_socket_outgoing_error(error_get_pretty(err));
+    migration_connect_error_propagate(data->s, err);
 }
 
 void socket_start_outgoing_migration(MigrationState *s,

migration/tls.c

@@ -104,16 +104,17 @@ static void migration_tls_outgoing_handshake(QIOTask *task,
                                              gpointer opaque)
 {
     MigrationState *s = opaque;
-    QIOChannel *ioc = QIO_CHANNEL(qio_task_get_source(task));
+    g_autoptr(QIOChannel) ioc = QIO_CHANNEL(qio_task_get_source(task));
     Error *err = NULL;
 
     if (qio_task_propagate_error(task, &err)) {
         trace_migration_tls_outgoing_handshake_error(error_get_pretty(err));
-    } else {
-        trace_migration_tls_outgoing_handshake_complete();
+        migration_connect_error_propagate(s, err);
+        return;
     }
-    migration_channel_connect(s, ioc, err);
-    object_unref(OBJECT(ioc));
+
+    trace_migration_tls_outgoing_handshake_complete();
+    migration_channel_connect(s, ioc);
 }
 
 QIOChannelTLS *migration_tls_client_create(QIOChannel *ioc,
@@ -129,8 +130,7 @@ QIOChannelTLS *migration_tls_client_create(QIOChannel *ioc,
     return qio_channel_tls_new_client(ioc, creds, migrate_tls_hostname(), errp);
 }
 
-void migration_tls_channel_connect(MigrationState *s,
-                                   QIOChannel *ioc,
+void migration_tls_channel_connect(MigrationState *s, QIOChannel *ioc,
                                    Error **errp)
 {
     QIOChannelTLS *tioc;

migration/tls.h

@@ -29,8 +29,7 @@ void migration_tls_channel_process_incoming(QIOChannel *ioc, Error **errp);
 QIOChannelTLS *migration_tls_client_create(QIOChannel *ioc,
                                            Error **errp);
 
-void migration_tls_channel_connect(MigrationState *s,
-                                   QIOChannel *ioc,
+void migration_tls_channel_connect(MigrationState *s, QIOChannel *ioc,
                                    Error **errp);
 void migration_tls_channel_end(QIOChannel *ioc, Error **errp);
 /* Whether the QIO channel requires further TLS handshake? */

migration/trace-events

@@ -204,7 +204,7 @@ migration_transferred_bytes(uint64_t qemu_file, uint64_t multifd, uint64_t rdma)
 
 # channel.c
 migration_set_incoming_channel(void *ioc, const char *ioctype) "ioc=%p ioctype=%s"
-migration_set_outgoing_channel(void *ioc, const char *ioctype, void *err)  "ioc=%p ioctype=%s err=%p"
+migration_set_outgoing_channel(void *ioc, const char *ioctype) "ioc=%p ioctype=%s"
 
 # global_state.c
 migrate_state_too_big(void) ""