Update RequestSpec.pci_request for resize

Nova uses the RequestSpec.pci_request in the PciPassthroughFilter to
decide if the PCI devicesm, requested via the pci_alias in the flavor
extra_spec, are available on a potential target host. During resize the
new flavor might contain different pci_alias request than the old flavor
of the instance. In this case Nova should use the pci_alias from the new
flavor to scheduler the destination host of the resize. However this
logic was missing and Nova used the old pci_request value based on the
old flavor. This patch adds the missing logic.

Closes-Bug: #1983753
Closes-Bug: #1941005
Change-Id: I73c9ae27e9c42ee211a53bed3d849650b65f08be

nova/compute/api.py

@@ -4227,6 +4227,19 @@ class API:
         if not same_flavor:
             request_spec.numa_topology = hardware.numa_get_constraints(
                 new_flavor, instance.image_meta)
+            # if the flavor is changed then we need to recalculate the
+            # pci_requests as well because the new flavor might request
+            # different pci_aliases
+            new_pci_requests = pci_request.get_pci_requests_from_flavor(
+                new_flavor)
+            new_pci_requests.instance_uuid = instance.uuid
+            # The neutron based InstancePCIRequest cannot change during resize,
+            # so we just need to copy them from the old request
+            for request in request_spec.pci_requests.requests or []:
+                if request.source == objects.InstancePCIRequest.NEUTRON_PORT:
+                    new_pci_requests.requests.append(request)
+            request_spec.pci_requests = new_pci_requests
+
             # TODO(huaqiang): Remove in Wallaby
             # check nova-compute nodes have been updated to Victoria to resize
             # instance to a new mixed instance from a dedicated or shared

nova/tests/functional/libvirt/test_pci_sriov_servers.py

@@ -1389,13 +1389,16 @@ class PCIServersTest(_PCIServersTestBase):
 
         # Resize it to a flavor without PCI devices. We expect this to work, as
         # test_compute1 is available.
-        # FIXME(artom) This is bug 1941005.
         flavor_id = self._create_flavor()
-        ex = self.assertRaises(client.OpenStackApiException,
-                               self._resize_server, server, flavor_id)
-        self.assertEqual(500, ex.response.status_code)
-        self.assertIn('NoValidHost', str(ex))
-        # self._confirm_resize(server)
+        with mock.patch(
+            'nova.virt.libvirt.driver.LibvirtDriver'
+            '.migrate_disk_and_power_off',
+            return_value='{}',
+        ):
+            self._resize_server(server, flavor_id)
+        self._confirm_resize(server)
+        self.assertPCIDeviceCounts('test_compute0', total=1, free=1)
+        self.assertPCIDeviceCounts('test_compute1', total=0, free=0)
 
     def _confirm_resize(self, server, host='host1'):
         # NOTE(sbauza): Unfortunately, _cleanup_resize() in libvirt checks the

nova/tests/functional/regressions/test_bug_1983753.py

@@ -16,7 +16,6 @@ import fixtures
 from oslo_serialization import jsonutils
 
 from nova.tests.fixtures import libvirt as fakelibvirt
-from nova.tests.functional.api import client
 from nova.tests.functional.libvirt import test_pci_sriov_servers
 
 
@@ -119,19 +118,10 @@ class TestPciResize(test_pci_sriov_servers._PCIServersTestBase):
             "compute2", total=num_pci_on_dest, free=num_pci_on_dest - 1)
 
     def test_resize_from_two_devs_to_one_dev_dest_has_two_devs(self):
-        # this works
         self._test_resize_from_two_devs_to_one_dev(num_pci_on_dest=2)
 
     def test_resize_from_two_devs_to_one_dev_dest_has_one_dev(self):
-        # This is bug 1983753 as nova uses the old InstancePciRequest during
-        # the scheduling and therefore tries to find a compute with two PCI
-        # devs even though the flavor only requests one.
-        ex = self.assertRaises(
-            client.OpenStackApiException,
-            self._test_resize_from_two_devs_to_one_dev,
-            num_pci_on_dest=1
-        )
-        self.assertIn('nova.exception.NoValidHost', str(ex))
+        self._test_resize_from_two_devs_to_one_dev(num_pci_on_dest=1)
 
     def test_resize_from_vf_to_pf(self):
         # The fake libvirt will emulate on the host:
@@ -181,13 +171,7 @@ class TestPciResize(test_pci_sriov_servers._PCIServersTestBase):
         # dev. This should fit to compute2 having exactly one PF dev.
         extra_spec = {"pci_passthrough:alias": "a-pf:1"}
         flavor_id = self._create_flavor(extra_spec=extra_spec)
-        # This is bug 1983753 as nova uses the old InstancePciRequest during
-        # the scheduling and therefore tries to find a compute with a VF dev
-        # even though the flavor only requests a PF dev.
-        ex = self.assertRaises(
-            client.OpenStackApiException,
-            self._resize_server,
-            server,
-            flavor_id=flavor_id,
-        )
-        self.assertIn('nova.exception.NoValidHost', str(ex))
+        self._resize_server(server, flavor_id=flavor_id)
+        self._confirm_resize(server)
+        self.assertPCIDeviceCounts("compute1", total=1, free=1)
+        self.assertPCIDeviceCounts("compute2", total=1, free=0)

nova/tests/unit/compute/test_api.py

@@ -2089,7 +2089,8 @@ class _ComputeAPIUnitTestMixIn(object):
                 filter_properties = {'ignore_hosts': [fake_inst['host']]}
 
             if request_spec:
-                fake_spec = objects.RequestSpec()
+                fake_spec = objects.RequestSpec(
+                    pci_requests=objects.InstancePCIRequests(requests=[]))
                 if requested_destination:
                     cell1 = objects.CellMapping(uuid=uuids.cell1, name='cell1')
                     fake_spec.requested_destination = objects.Destination(