migration: simplify blockers

Modify migrate_add_blocker and migrate_del_blocker to take an Error **
reason.  This allows migration to own the Error object, so that if
an error occurs in migrate_add_blocker, migration code can free the Error
and clear the client handle, simplifying client code.  It also simplifies
the migrate_del_blocker call site.

In addition, this is a pre-requisite for a proposed future patch that would
add a mode argument to migration requests to support live update, and
maintain a list of blockers for each mode.  A blocker may apply to a single
mode or to multiple modes, and passing Error** will allow one Error object
to be registered for multiple modes.

No functional change.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Tested-by: Michael Galaxy <mgalaxy@akamai.com>
Reviewed-by: Michael Galaxy <mgalaxy@akamai.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <1697634216-84215-1-git-send-email-steven.sistare@oracle.com>

1 files changed, 2 insertions, 14 deletions

diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
index da43dcd..0aaad65 100644
--- a/hw/vfio/migration.c
+++ b/hw/vfio/migration.c
@@ -891,8 +891,6 @@ static void vfio_migration_deinit(VFIODevice *vbasedev)
 
 static int vfio_block_migration(VFIODevice *vbasedev, Error *err, Error **errp)
 {
-    int ret;
-
     if (vbasedev->enable_migration == ON_OFF_AUTO_ON) {
         error_propagate(errp, err);
         return -EINVAL;
@@ -901,13 +899,7 @@ static int vfio_block_migration(VFIODevice *vbasedev, Error *err, Error **errp)
     vbasedev->migration_blocker = error_copy(err);
     error_free(err);
 
-    ret = migrate_add_blocker(vbasedev->migration_blocker, errp);
-    if (ret < 0) {
-        error_free(vbasedev->migration_blocker);
-        vbasedev->migration_blocker = NULL;
-    }
-
-    return ret;
+    return migrate_add_blocker(&vbasedev->migration_blocker, errp);
 }
 
 /* ---------------------------------------------------------------------- */
@@ -994,9 +986,5 @@ void vfio_migration_exit(VFIODevice *vbasedev)
         vfio_migration_deinit(vbasedev);
     }
 
-    if (vbasedev->migration_blocker) {
-        migrate_del_blocker(vbasedev->migration_blocker);
-        error_free(vbasedev->migration_blocker);
-        vbasedev->migration_blocker = NULL;
-    }
+    migrate_del_blocker(&vbasedev->migration_blocker);
 }