diff --git a/nova/objects/request_spec.py b/nova/objects/request_spec.py
index 7d57903078..a3efbd0bf5 100644
--- a/nova/objects/request_spec.py
+++ b/nova/objects/request_spec.py
@@ -1293,16 +1293,55 @@ class RequestLevelParams(base.NovaObject):
     RequestGroup).
     """
     # Version 1.0: Initial version
-    VERSION = '1.0'
+    # Version 1.1: Add same_subtree field
+    VERSION = '1.1'
 
     fields = {
         # Traits required on the root provider
         'root_required': fields.SetOfStringsField(default=set()),
         # Traits forbidden on the root provider
         'root_forbidden': fields.SetOfStringsField(default=set()),
+        # Lists of request group suffixes that needs to be allocated from the
+        # same provider subtree
+        'same_subtree': fields.ListOfListsOfStringsField(default=list()),
         # NOTE(efried): group_policy would be appropriate to include here, once
         # we have a use case for it.
     }
 
     def obj_load_attr(self, attrname):
         self.obj_set_defaults(attrname)
+
+    def obj_make_compatible(self, primitive, target_version):
+        super().obj_make_compatible(primitive, target_version)
+
+        target_version = versionutils.convert_version_to_tuple(target_version)
+        if target_version < (1, 1):
+            if 'same_subtree' in primitive:
+                del primitive['same_subtree']
+
+    @classmethod
+    def from_port_request(cls, port_resource_request):
+        """Extracts request level global parameters from the resource_request
+        of a neutron port.
+
+        Neutron only uses same_subtree at the moment.
+        """
+        same_subtree = port_resource_request.get('same_subtree')
+        if same_subtree:
+            # NOTE(gibi): A single port only has a single list of groups
+            # requesting same subtree, but the RequestLevelParams maintains a
+            # list of such subtree requests
+            return cls(same_subtree=[same_subtree])
+
+        return cls()
+
+    def extend_with(self, other_req_lvl_params):
+        """Extends the existing object with parameter values from another
+        RequestLevelParams object. That new set of requirements are connected
+        with the existing ones with a logical AND operation.
+        """
+        self.root_required = self.root_required.union(
+            other_req_lvl_params.root_required)
+        self.root_forbidden = self.root_forbidden.union(
+            other_req_lvl_params.root_forbidden)
+        self.same_subtree.extend(other_req_lvl_params.same_subtree)
diff --git a/nova/tests/unit/objects/test_objects.py b/nova/tests/unit/objects/test_objects.py
index bb7e879224..4e16baeaa1 100644
--- a/nova/tests/unit/objects/test_objects.py
+++ b/nova/tests/unit/objects/test_objects.py
@@ -1123,7 +1123,7 @@ object_data = {
     'Quotas': '1.3-3b2b91371f60e788035778fc5f87797d',
     'QuotasNoOp': '1.3-d1593cf969c81846bc8192255ea95cce',
     'RequestGroup': '1.3-0458d350a8ec9d0673f9be5640a990ce',
-    'RequestLevelParams': '1.0-1e5c8c18bd44cd233c8b32509c99d06f',
+    'RequestLevelParams': '1.1-3a718a0ae0bfdec669e7108631b3f313',
     'RequestSpec': '1.14-2cdbda368ca07e10905dc5fe96908a58',
     'Resource': '1.0-d8a2abbb380da583b995fd118f6a8953',
     'ResourceList': '1.0-4a53826625cc280e15fae64a575e0879',
diff --git a/nova/tests/unit/objects/test_request_spec.py b/nova/tests/unit/objects/test_request_spec.py
index 7edc84bf62..2963909c32 100644
--- a/nova/tests/unit/objects/test_request_spec.py
+++ b/nova/tests/unit/objects/test_request_spec.py
@@ -1692,3 +1692,54 @@ class TestMappingRequestGroupsToProviders(test.NoDBTestCase):
             allocations, provider_traits)
 
         self.assertIn('allocations leftover', mock_debug.mock_calls[3][1][0])
+
+
+class TestRequestLevelParams(test.NoDBTestCase):
+    def setUp(self):
+        super().setUp()
+        self.user_id = uuids.user_id
+        self.project_id = uuids.project_id
+        self.context = context.RequestContext(uuids.user_id, uuids.project_id)
+
+    def test_obj_make_compatible(self):
+        obj = request_spec.RequestLevelParams(
+            self.context,
+            root_required={"CUSTOM_FOO", "CUSTOM_BAR"},
+            root_forbidden={"CUSTOM_BAZ"},
+            same_subtree=[["group1", "group2"], ["group3", "group4"]])
+
+        manifest = ovo_base.obj_tree_get_versions(obj.obj_name())
+
+        obj_primitive = obj.obj_to_primitive(
+            target_version='1.1',
+            version_manifest=manifest)['nova_object.data']
+        self.assertIn('root_required', obj_primitive)
+        self.assertIn('root_forbidden', obj_primitive)
+        self.assertIn('same_subtree', obj_primitive)
+
+        obj_primitive = obj.obj_to_primitive(
+            target_version='1.0',
+            version_manifest=manifest)['nova_object.data']
+        self.assertIn('root_required', obj_primitive)
+        self.assertIn('root_forbidden', obj_primitive)
+        self.assertNotIn('same_subtree', obj_primitive)
+
+    def test_extend_with(self):
+        obj1 = request_spec.RequestLevelParams(
+            self.context,
+            root_required={"CUSTOM_FOO"},
+            root_forbidden={"CUSTOM_BAZ"},
+            same_subtree=[["group1", "group2"]])
+        obj2 = request_spec.RequestLevelParams(
+            self.context,
+            root_required={"CUSTOM_BAR"},
+            root_forbidden={"CUSTOM_FOOBAR"},
+            same_subtree=[["group3", "group4"]])
+
+        obj1.extend_with(obj2)
+
+        self.assertEqual({"CUSTOM_FOO", "CUSTOM_BAR"}, obj1.root_required)
+        self.assertEqual({"CUSTOM_BAZ", "CUSTOM_FOOBAR"}, obj1.root_forbidden)
+        self.assertEqual(
+            [["group1", "group2"], ["group3", "group4"]],
+            obj1.same_subtree)