Add traits for viommu model

* Add iommu model trait for viommu model

* Add ``hw_viommu_model`` to request_filter, this will extend the
  transform_image_metadata prefilter to select host with the correct model.

* Provide new compute ``COMPUTE_VIOMMU_MODEL_*`` capablity trait for each model
  it supports in driver.

Implements: blueprint libvirt-viommu-device
Depends-On: https://review.opendev.org/c/openstack/os-traits/+/844336
Change-Id: I2caa1a9c473a2b11c287061280b4a78edb96f859

nova/scheduler/request_filter.py

@@ -214,6 +214,7 @@ def transform_image_metadata(ctxt, request_spec):
         'hw_vif_model': 'COMPUTE_NET_VIF_MODEL',
         'hw_architecture': 'HW_ARCH',
         'hw_emulation_architecture': 'COMPUTE_ARCH',
+        'hw_viommu_model': 'COMPUTE_VIOMMU',
     }
 
     trait_names = []

nova/tests/unit/virt/libvirt/test_config.py

@@ -4156,7 +4156,8 @@ class LibvirtConfigDomainCapsDevicesTests(LibvirtConfigBaseTest):
         obj.parse_str(xml)
         # we only use the video and disk devices today.
         device_types = [config.LibvirtConfigDomainCapsDiskBuses,
-                        config.LibvirtConfigDomainCapsVideoModels]
+                        config.LibvirtConfigDomainCapsVideoModels,
+                        ]
         # so we assert there are only two device types parsed
         self.assertEqual(2, len(obj.devices))
         # we then assert that the parsed devices are of the correct type

nova/tests/unit/virt/libvirt/test_driver.py

@@ -961,9 +961,10 @@ class LibvirtConnTestCase(test.NoDBTestCase,
     @mock.patch.object(libvirt_driver.LibvirtDriver, '_get_storage_bus_traits')
     @mock.patch.object(libvirt_driver.LibvirtDriver, '_get_video_model_traits')
     @mock.patch.object(libvirt_driver.LibvirtDriver, '_get_vif_model_traits')
+    @mock.patch.object(host.Host, "has_min_version")
     def test_static_traits(
-        self, mock_vif_traits, mock_video_traits, mock_storage_traits,
-        mock_cpu_traits,
+        self, mock_version, mock_vif_traits, mock_video_traits,
+        mock_storage_traits, mock_cpu_traits,
     ):
         """Ensure driver capabilities are correctly retrieved and cached."""
 
@@ -974,14 +975,21 @@ class LibvirtConnTestCase(test.NoDBTestCase,
         mock_video_traits.return_value = {'COMPUTE_GRAPHICS_MODEL_VGA': True}
         mock_vif_traits.return_value = {'COMPUTE_NET_VIF_MODEL_VIRTIO': True}
 
+        # for support COMPUTE_VIOMMU_MODEL_VIRTIO
+        mock_version.return_value = True
+
         drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), False)
         expected = {
-            'HW_CPU_HYPERTHREADING': True,
-            'COMPUTE_STORAGE_BUS_VIRTIO': True,
             'COMPUTE_GRAPHICS_MODEL_VGA': True,
             'COMPUTE_NET_VIF_MODEL_VIRTIO': True,
             'COMPUTE_SECURITY_TPM_1_2': False,
             'COMPUTE_SECURITY_TPM_2_0': False,
+            'COMPUTE_STORAGE_BUS_VIRTIO': True,
+            'COMPUTE_VIOMMU_MODEL_AUTO': True,
+            'COMPUTE_VIOMMU_MODEL_INTEL': True,
+            'COMPUTE_VIOMMU_MODEL_SMMUV3': True,
+            'COMPUTE_VIOMMU_MODEL_VIRTIO': True,
+            'HW_CPU_HYPERTHREADING': True
         }
 
         static_traits = drvr.static_traits
@@ -1027,6 +1035,10 @@ class LibvirtConnTestCase(test.NoDBTestCase,
             'COMPUTE_NET_VIF_MODEL_VIRTIO': True,
             'COMPUTE_SECURITY_TPM_1_2': False,
             'COMPUTE_SECURITY_TPM_2_0': False,
+            'COMPUTE_VIOMMU_MODEL_AUTO': True,
+            'COMPUTE_VIOMMU_MODEL_INTEL': True,
+            'COMPUTE_VIOMMU_MODEL_SMMUV3': True,
+            'COMPUTE_VIOMMU_MODEL_VIRTIO': False
         }
 
         static_traits = drvr.static_traits

nova/virt/libvirt/driver.py

@@ -8922,6 +8922,7 @@ class LibvirtDriver(driver.ComputeDriver):
         traits.update(self._get_storage_bus_traits())
         traits.update(self._get_video_model_traits())
         traits.update(self._get_vif_model_traits())
+        traits.update(self._get_iommu_model_traits())
         traits.update(self._get_tpm_traits())
 
         _, invalid_traits = ot.check_traits(traits)
@@ -12198,6 +12199,30 @@ class LibvirtDriver(driver.ComputeDriver):
             in supported_models for model in all_models
         }
 
+    def _get_iommu_model_traits(self) -> ty.Dict[str, bool]:
+        """Get iommu model traits based on the currently enabled virt_type.
+        Not all traits generated by this function may be valid and the result
+        should be validated.
+        :return: A dict of trait names mapped to boolean values.
+        """
+        dom_caps = self._host.get_domain_capabilities()
+        supported_models: ty.Set[str] = {fields.VIOMMUModel.AUTO}
+        # our min version of qemu/libvirt supprot q35 and virt machine types.
+        # They also support the smmuv3 and intel iommu modeles so if the qemu
+        # binary is avaiable we can report the trait.
+        if fields.Architecture.AARCH64 in dom_caps:
+            supported_models.add(fields.VIOMMUModel.SMMUV3)
+        if fields.Architecture.X86_64 in dom_caps:
+            supported_models.add(fields.VIOMMUModel.INTEL)
+        # the virtio iommu model requires a newer libvirt then our min
+        # libvirt so we need to check the version explcitly.
+        if self._host.has_min_version(MIN_LIBVIRT_VIOMMU_VIRTIO_MODEL):
+            supported_models.add(fields.VIOMMUModel.VIRTIO)
+        return {
+            f'COMPUTE_VIOMMU_MODEL_{model.replace("-", "_").upper()}': model
+            in supported_models for model in fields.VIOMMUModel.ALL
+        }
+
     def _get_storage_bus_traits(self) -> ty.Dict[str, bool]:
         """Get storage bus traits based on the currently enabled virt_type.