diff --git a/nova/cmd/manage.py b/nova/cmd/manage.py
index 75d252b1ae37..e84d4ef1f7b8 100644
--- a/nova/cmd/manage.py
+++ b/nova/cmd/manage.py
@@ -56,6 +56,7 @@ from nova import exception
 from nova.i18n import _
 from nova import objects
 from nova.objects import aggregate as aggregate_obj
+from nova.objects import block_device as block_device_obj
 from nova.objects import build_request as build_request_obj
 from nova.objects import host_mapping as host_mapping_obj
 from nova.objects import instance as instance_obj
@@ -436,6 +437,8 @@ class DbCommands(object):
         quotas_obj.migrate_quota_classes_to_api_db,
         # Added in Queens
         sa_db.migration_migrate_to_uuid,
+        # Added in Queens
+        block_device_obj.BlockDeviceMapping.populate_uuids,
     )
 
     def __init__(self):
diff --git a/nova/objects/block_device.py b/nova/objects/block_device.py
index 866109d47bdf..340128c512a5 100644
--- a/nova/objects/block_device.py
+++ b/nova/objects/block_device.py
@@ -104,6 +104,22 @@ class BlockDeviceMapping(base.NovaPersistentObject, base.NovaObject,
         if target_version < (1, 17) and 'tag' in primitive:
             del primitive['tag']
 
+    @classmethod
+    def populate_uuids(cls, context, count):
+        @db_api.pick_context_manager_reader
+        def get_bdms_no_uuid(context):
+            return context.session.query(db_models.BlockDeviceMapping).\
+                    filter_by(uuid=None).limit(count).all()
+
+        db_bdms = get_bdms_no_uuid(context)
+
+        done = 0
+        for db_bdm in db_bdms:
+            cls._create_uuid(context, db_bdm['id'])
+            done += 1
+
+        return done, done
+
     @staticmethod
     @oslo_db_api.wrap_db_retry(max_retries=1, retry_on_deadlock=True)
     def _create_uuid(context, bdm_id):
diff --git a/nova/tests/unit/objects/test_block_device.py b/nova/tests/unit/objects/test_block_device.py
index fd6681589452..574384383e63 100644
--- a/nova/tests/unit/objects/test_block_device.py
+++ b/nova/tests/unit/objects/test_block_device.py
@@ -483,6 +483,40 @@ class TestBlockDeviceMappingUUIDMigration(test.TestCase):
 
         self.assertEqual(uuid1, uuid2)
 
+    def _assert_online_migration(self, expected_total, expected_done,
+                                 limit=10):
+        total, done = objects.BlockDeviceMapping.populate_uuids(
+                self.context, limit)
+        self.assertEqual(expected_total, total)
+        self.assertEqual(expected_done, done)
+
+    def test_online_migration(self):
+        self._assert_online_migration(0, 0)
+
+        # Create 2 BDMs, one with a uuid and one without
+        self._create_legacy_bdm(self.context)
+        db_api.block_device_mapping_create(self.context,
+                {'uuid': uuids.bdm2, 'instance_uuid': uuids.instance_uuid},
+                legacy=False)
+
+        # Run the online migration. We should find 1 and update 1
+        self._assert_online_migration(1, 1)
+
+        # Fetch the BDMs and check we didn't modify the uuid of bdm2
+        bdms = objects.BlockDeviceMappingList.get_by_instance_uuid(
+                self.context, uuids.instance_uuid)
+        bdm_uuids = [bdm.uuid for bdm in bdms]
+        self.assertIn(uuids.bdm2, bdm_uuids)
+        self.assertNotIn(None, bdm_uuids)
+
+        # Run the online migration again to see nothing was processed
+        self._assert_online_migration(0, 0)
+
+        # Test that we don't migrate more than the limit
+        for i in range(0, 3):
+            self._create_legacy_bdm(self.context)
+        self._assert_online_migration(2, 2, limit=2)
+
 
 class TestBlockDeviceMappingObject(test_objects._LocalTest,
                                    _TestBlockDeviceMappingObject):