libvirt: Add vIOMMU device to guest

Implementation for BP/libvirt-viommu-device.
With provide `hw:viommu_model` property to extra_specs or
`hw_viommu_model` to image property. will enable viommu to libvirt
guest.

[1] https://www.berrange.com/posts/2017/02/16/setting-up-a-nested-kvm-guest-for-developing-testing-pci-device-assignment-with-numa/
[2] https://review.opendev.org/c/openstack/nova-specs/+/840310

Implements: blueprint libvirt-viommu-device
Change-Id: Ief9c550292788160433a28a7a1c36ba38a6bc849
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

17 files changed, 801 insertions, 144 deletions

diff --git a/doc/notification_samples/common_payloads/ImageMetaPropsPayload.json b/doc/notification_samples/common_payloads/ImageMetaPropsPayload.json
index 6aa4d9cbe5..cdde7d3097 100644
--- a/doc/notification_samples/common_payloads/ImageMetaPropsPayload.json
+++ b/doc/notification_samples/common_payloads/ImageMetaPropsPayload.json
@@ -4,5 +4,5 @@
         "hw_architecture": "x86_64"
     },
     "nova_object.name": "ImageMetaPropsPayload",
-    "nova_object.version": "1.11"
+    "nova_object.version": "1.12"
 }
diff --git a/doc/source/admin/pci-passthrough.rst b/doc/source/admin/pci-passthrough.rst
index aecf0c9e3f..32287fd789 100644
--- a/doc/source/admin/pci-passthrough.rst
+++ b/doc/source/admin/pci-passthrough.rst
@@ -395,3 +395,61 @@ be added to the resource provider representing the matching PCI devices.
    It is suggested to use the PCI address of the device instead.
 
 For deeper technical details please read the `nova specification. <https://specs.openstack.org/openstack/nova-specs/specs/zed/approved/pci-device-tracking-in-placement.html>`_
+
+
+Virtual IOMMU support
+---------------------
+
+With provided :nova:extra-spec:`hw:viommu_model` flavor extra spec or equivalent
+image metadata property ``hw_viommu_model`` and with the guest CPU architecture
+and OS allows, we can enable vIOMMU in libvirt driver.
+
+.. note::
+
+    Enable vIOMMU might introduce significant performance overhead.
+    You can see performance comparision table from
+    `AMD vIOMMU session on KVM Forum 2021`_.
+    For the above reason, vIOMMU should only be enabled for workflow that
+    require it.
+
+.. _`AMD vIOMMU session on KVM Forum 2021`: https://static.sched.com/hosted_files/kvmforum2021/da/vIOMMU%20KVM%20Forum%202021%20-%20v4.pdf
+
+Here are four possible values allowed for ``hw:viommu_model``
+(and ``hw_viommu_model``):
+
+**virtio**
+    Supported on Libvirt since 8.3.0, for Q35 and ARM virt guests.
+
+**smmuv3**
+    Supported on Libvirt since 5.5.0, for ARM virt guests.
+**intel**
+    Supported for for Q35 guests.
+
+**auto**
+    This option will translate to ``virtio`` if Libvirt supported,
+    else ``intel`` on X86 (Q35) and ``smmuv3`` on AArch64.
+
+For the viommu attributes:
+
+* ``intremap``, ``caching_mode``, and ``iotlb``
+  options for viommu (These attributes are driver attributes defined in
+  `Libvirt IOMMU Domain`_) will direcly enabled.
+
+* ``eim`` will directly enabled if machine type is Q35.
+  ``eim`` is driver attribute defined in `Libvirt IOMMU Domain`_.
+
+.. note::
+
+    eim(Extended Interrupt Mode) attribute (with possible values on and off)
+    can be used to configure Extended Interrupt Mode.
+    A q35 domain with split I/O APIC (as described in hypervisor features),
+    and both interrupt remapping and EIM turned on for the IOMMU, will be
+    able to use more than 255 vCPUs. Since 3.4.0 (QEMU/KVM only).
+
+* ``aw_bits`` attribute can used to set the address width to allow mapping
+  larger iova addresses in the guest. Since Qemu current supported
+  values are 39 and 48, we directly set this to larger width (48)
+  if Libvirt supported.
+  ``aw_bits`` is driver attribute defined in `Libvirt IOMMU Domain`_.
+
+.. _`Libvirt IOMMU Domain`: https://libvirt.org/formatdomain.html#iommu-devices
diff --git a/nova/api/validation/extra_specs/hw.py b/nova/api/validation/extra_specs/hw.py
index 02e8de9cf2..c0c8f02809 100644
--- a/nova/api/validation/extra_specs/hw.py
+++ b/nova/api/validation/extra_specs/hw.py
@@ -511,6 +511,22 @@ feature_flag_validators = [
             ],
         },
     ),
+    base.ExtraSpecValidator(
+        name='hw:viommu_model',
+        description=(
+            'This can be used to set model for virtual IOMMU device.'
+        ),
+        value={
+            'type': str,
+            'enum': [
+                'intel',
+                'smmuv3',
+                'virtio',
+                'auto'
+            ],
+            'description': 'model for vIOMMU',
+        },
+    ),
 ]
 
 ephemeral_encryption_validators = [
diff --git a/nova/exception.py b/nova/exception.py
index fe3c12d870..077c3ef502 100644
--- a/nova/exception.py
+++ b/nova/exception.py
@@ -207,6 +207,16 @@ class Invalid(NovaException):
     code = 400
 
 
+class InvalidVIOMMUMachineType(Invalid):
+    msg_fmt = _("vIOMMU is not supported by Current machine type %(mtype)s "
+                "(Architecture: %(arch)s).")
+
+
+class InvalidVIOMMUArchitecture(Invalid):
+    msg_fmt = _("vIOMMU required either x86 or AArch64 architecture, "
+                "but given architecture %(arch)s.")
+
+
 class InvalidConfiguration(Invalid):
     msg_fmt = _("Configuration is Invalid.")
 
diff --git a/nova/notifications/objects/image.py b/nova/notifications/objects/image.py
index a408b27eab..01c86d1cb0 100644
--- a/nova/notifications/objects/image.py
+++ b/nova/notifications/objects/image.py
@@ -129,7 +129,8 @@ class ImageMetaPropsPayload(base.NotificationPayloadBase):
     # Version 1.10: Added 'hw_ephemeral_encryption' and
     #                     'hw_ephemeral_encryption_format' fields
     # Version 1.11: Added 'hw_locked_memory' field
-    VERSION = '1.11'
+    # Version 1.12: Added 'hw_viommu_model' field
+    VERSION = '1.12'
 
     SCHEMA = {
         k: ('image_meta_props', k) for k in image_meta.ImageMetaProps.fields}
diff --git a/nova/objects/fields.py b/nova/objects/fields.py
index 2946d2bd99..cae1ea4a4d 100644
--- a/nova/objects/fields.py
+++ b/nova/objects/fields.py
@@ -616,6 +616,16 @@ class VIFModel(BaseNovaEnum):
         return super(VIFModel, self).coerce(obj, attr, value)
 
 
+class VIOMMUModel(BaseNovaEnum):
+
+    INTEL = 'intel'
+    SMMUV3 = 'smmuv3'
+    VIRTIO = 'virtio'
+    AUTO = 'auto'
+
+    ALL = (INTEL, SMMUV3, VIRTIO, AUTO)
+
+
 class VMMode(BaseNovaEnum):
     """Represents possible vm modes for instances.
 
@@ -1301,6 +1311,10 @@ class VIFModelField(BaseEnumField):
     AUTO_TYPE = VIFModel()
 
 
+class VIOMMUModelField(BaseEnumField):
+    AUTO_TYPE = VIOMMUModel()
+
+
 class VMModeField(BaseEnumField):
     AUTO_TYPE = VMMode()
 
diff --git a/nova/objects/image_meta.py b/nova/objects/image_meta.py
index 0ca8ed571f..7927ad2575 100644
--- a/nova/objects/image_meta.py
+++ b/nova/objects/image_meta.py
@@ -191,14 +191,17 @@ class ImageMetaProps(base.NovaObject):
     # Version 1.32: Added 'hw_ephemeral_encryption' and
     #                     'hw_ephemeral_encryption_format' fields
     # Version 1.33: Added 'hw_locked_memory' field
+    # Version 1.34: Added 'hw_viommu_model' field
     # NOTE(efried): When bumping this version, the version of
     # ImageMetaPropsPayload must also be bumped. See its docstring for details.
-    VERSION = '1.33'
+    VERSION = '1.34'
 
     def obj_make_compatible(self, primitive, target_version):
         super(ImageMetaProps, self).obj_make_compatible(primitive,
                                                         target_version)
         target_version = versionutils.convert_version_to_tuple(target_version)
+        if target_version < (1, 34):
+            primitive.pop('hw_viommu_model', None)
         if target_version < (1, 33):
             primitive.pop('hw_locked_memory', None)
         if target_version < (1, 32):
@@ -446,6 +449,9 @@ class ImageMetaProps(base.NovaObject):
         # name of a NIC device model eg virtio, e1000, rtl8139
         'hw_vif_model': fields.VIFModelField(),
 
+        # name of IOMMU device model eg virtio, intel, smmuv3, or auto
+        'hw_viommu_model': fields.VIOMMUModelField(),
+
         # "xen" vs "hvm"
         'hw_vm_mode': fields.VMModeField(),
 
diff --git a/nova/tests/functional/notification_sample_tests/test_instance.py b/nova/tests/functional/notification_sample_tests/test_instance.py
index e6c88be239..f671a8abca 100644
--- a/nova/tests/functional/notification_sample_tests/test_instance.py
+++ b/nova/tests/functional/notification_sample_tests/test_instance.py
@@ -1231,7 +1231,7 @@ class TestInstanceNotificationSample(
                     'nova_object.data': {},
                     'nova_object.name': 'ImageMetaPropsPayload',
                     'nova_object.namespace': 'nova',
-                    'nova_object.version': '1.11',
+                    'nova_object.version': '1.12',
                 },
                 'image.size': 58145823,
                 'image.tags': [],
@@ -1327,7 +1327,7 @@ class TestInstanceNotificationSample(
                     'nova_object.data': {},
                     'nova_object.name': 'ImageMetaPropsPayload',
                     'nova_object.namespace': 'nova',
-                    'nova_object.version': '1.11',
+                    'nova_object.version': '1.12',
                 },
                 'image.size': 58145823,
                 'image.tags': [],
diff --git a/nova/tests/unit/api/validation/extra_specs/test_validators.py b/nova/tests/unit/api/validation/extra_specs/test_validators.py
index dd45f85ff1..a8911aadad 100644
--- a/nova/tests/unit/api/validation/extra_specs/test_validators.py
+++ b/nova/tests/unit/api/validation/extra_specs/test_validators.py
@@ -74,6 +74,10 @@ class TestValidators(test.NoDBTestCase):
             ('hw:pci_numa_affinity_policy', 'preferred'),
             ('hw:pci_numa_affinity_policy', 'socket'),
             ('hw:cpu_policy', 'mixed'),
+            ('hw:viommu_model', 'auto'),
+            ('hw:viommu_model', 'intel'),
+            ('hw:viommu_model', 'smmuv3'),
+            ('hw:viommu_model', 'virtio'),
         )
         for key, value in valid_specs:
             validators.validate(key, value)
@@ -92,6 +96,7 @@ class TestValidators(test.NoDBTestCase):
             ('hw:pci_numa_affinity_policy', 'requird'),
             ('hw:pci_numa_affinity_policy', 'prefrred'),
             ('hw:pci_numa_affinity_policy', 'socet'),
+            ('hw:viommu_model', 'autt'),
         )
         for key, value in invalid_specs:
             with testtools.ExpectedException(exception.ValidationError):
diff --git a/nova/tests/unit/notifications/objects/test_notification.py b/nova/tests/unit/notifications/objects/test_notification.py
index 41352f2e48..de9e6f2762 100644
--- a/nova/tests/unit/notifications/objects/test_notification.py
+++ b/nova/tests/unit/notifications/objects/test_notification.py
@@ -386,7 +386,7 @@ notification_object_data = {
     # ImageMetaProps, so when you see a fail here for that reason, you must
     # *also* bump the version of ImageMetaPropsPayload. See its docstring for
     # more information.
-    'ImageMetaPropsPayload': '1.11-938809cd33367c52cbc814fb9b6783dc',
+    'ImageMetaPropsPayload': '1.12-b9c64832d7772c1973e913bacbe0e8f9',
     'InstanceActionNotification': '1.0-a73147b93b520ff0061865849d3dfa56',
     'InstanceActionPayload': '1.8-4fa3da9cbf0761f1f700ae578f36dc2f',
     'InstanceActionRebuildNotification':
diff --git a/nova/tests/unit/objects/test_image_meta.py b/nova/tests/unit/objects/test_image_meta.py
index 27d91290ad..371f7b101a 100644
--- a/nova/tests/unit/objects/test_image_meta.py
+++ b/nova/tests/unit/objects/test_image_meta.py
@@ -538,3 +538,19 @@ class TestImageMetaProps(test.NoDBTestCase):
             hw_pci_numa_affinity_policy=fields.PCINUMAAffinityPolicy.SOCKET)
         self.assertRaises(exception.ObjectActionError,
                           obj.obj_to_primitive, '1.27')
+
+    def test_obj_make_compatible_viommu_model(self):
+        """Check 'hw_viommu_model' compatibility."""
+        # assert that 'hw_viommu_model' is supported on a suitably new version
+        obj = objects.ImageMetaProps(
+            hw_viommu_model=objects.fields.VIOMMUModel.VIRTIO,
+        )
+        primitive = obj.obj_to_primitive('1.34')
+        self.assertIn('hw_viommu_model', primitive['nova_object.data'])
+        self.assertEqual(
+            objects.fields.VIOMMUModel.VIRTIO,
+            primitive['nova_object.data']['hw_viommu_model'])
+
+        # and is absent on older versions
+        primitive = obj.obj_to_primitive('1.33')
+        self.assertNotIn('hw_viommu_model', primitive['nova_object.data'])
diff --git a/nova/tests/unit/objects/test_objects.py b/nova/tests/unit/objects/test_objects.py
index f42b74e135..951ae00f7d 100644
--- a/nova/tests/unit/objects/test_objects.py
+++ b/nova/tests/unit/objects/test_objects.py
@@ -1072,7 +1072,7 @@ object_data = {
     'HyperVLiveMigrateData': '1.4-e265780e6acfa631476c8170e8d6fce0',
     'IDEDeviceBus': '1.0-29d4c9f27ac44197f01b6ac1b7e16502',
     'ImageMeta': '1.8-642d1b2eb3e880a367f37d72dd76162d',
-    'ImageMetaProps': '1.33-6b7a29f769e6b8eee3f05832d78c85a2',
+    'ImageMetaProps': '1.34-29b3a6b7fe703f36bfd240d914f16c21',
     'Instance': '2.7-d187aec68cad2e4d8b8a03a68e4739ce',
     'InstanceAction': '1.2-9a5abc87fdd3af46f45731960651efb5',
     'InstanceActionEvent': '1.4-5b1f361bd81989f8bb2c20bb7e8a4cb4',
diff --git a/nova/tests/unit/virt/libvirt/test_config.py b/nova/tests/unit/virt/libvirt/test_config.py
index 4b258a2464..6cc67fba54 100644
--- a/nova/tests/unit/virt/libvirt/test_config.py
+++ b/nova/tests/unit/virt/libvirt/test_config.py
@@ -16,6 +16,7 @@ from lxml import etree
 from oslo_utils.fixture import uuidsentinel as uuids
 from oslo_utils import units
 
+from nova import exception
 from nova.objects import fields as obj_fields
 from nova import test
 from nova.tests.fixtures import libvirt_data as fake_libvirt_data
@@ -70,6 +71,23 @@ class LibvirtConfigTest(LibvirtConfigBaseTest):
         obj = config.LibvirtConfigObject(root_name="demo")
         obj.parse_str(inxml)
 
+    def test_parse_on_off_str(self):
+        obj = config.LibvirtConfigObject(root_name="demo")
+        self.assertTrue(obj.parse_on_off_str('on'))
+        self.assertFalse(obj.parse_on_off_str('off'))
+        self.assertFalse(obj.parse_on_off_str(None))
+        self.assertRaises(exception.InvalidInput, obj.parse_on_off_str, 'foo')
+
+    def test_get_yes_no_str(self):
+        obj = config.LibvirtConfigObject(root_name="demo")
+        self.assertEqual('yes', obj.get_yes_no_str(True))
+        self.assertEqual('no', obj.get_yes_no_str(False))
+
+    def test_get_on_off_str(self):
+        obj = config.LibvirtConfigObject(root_name="demo")
+        self.assertEqual('on', obj.get_on_off_str(True))
+        self.assertEqual('off', obj.get_on_off_str(False))
+
 
 class LibvirtConfigCapsTest(LibvirtConfigBaseTest):
 
@@ -2365,6 +2383,13 @@ class LibvirtConfigGuestFeatureTest(LibvirtConfigBaseTest):
             xml = obj.to_xml()
             self.assertXmlEqual(xml, "<pmu state='off'/>")
 
+    def test_feature_ioapic(self):
+        obj = config.LibvirtConfigGuestFeatureIOAPIC()
+        obj.driver = "libvirt"
+
+        xml = obj.to_xml()
+        self.assertXmlEqual(xml, "<ioapic driver='libvirt'/>")
+
 
 class LibvirtConfigGuestTest(LibvirtConfigBaseTest):
 
@@ -3993,6 +4018,28 @@ class LibvirtConfigGuestVPMEMTest(LibvirtConfigBaseTest):
           </memory>""")
 
 
+class LibvirtConfigGuestIOMMUTest(LibvirtConfigBaseTest):
+
+    def test_config_iommu(self):
+        obj = config.LibvirtConfigGuestIOMMU()
+        obj.model = "intel"
+        obj.interrupt_remapping = True
+        obj.caching_mode = True
+        obj.aw_bits = 48
+        obj.eim = True
+        obj.iotlb = True
+
+        xml = obj.to_xml()
+        self.assertXmlEqual(
+            xml,
+            """
+<iommu model='intel'>
+  <driver intremap='on' caching_mode='on' aw_bits='48' eim='on' iotlb='on'/>
+</iommu>
+            """,
+        )
+
+
 class LibvirtConfigDomainCapsVideoModelsTests(LibvirtConfigBaseTest):
 
     def test_parse_video_model(self):
diff --git a/nova/tests/unit/virt/libvirt/test_driver.py b/nova/tests/unit/virt/libvirt/test_driver.py
index b90d6a2ef6..1b349205cc 100644
--- a/nova/tests/unit/virt/libvirt/test_driver.py
+++ b/nova/tests/unit/virt/libvirt/test_driver.py
@@ -2566,6 +2566,11 @@ class LibvirtConnTestCase(test.NoDBTestCase,
 
     @mock.patch.object(time, "time")
     def test_get_guest_config(self, time_mock):
+        """Generate a "standard" guest with minimal configuration.
+
+        This uses i440fx by default since that's our default machine type and
+        x86 is our default architecture (in our test env, anyway).
+        """
         time_mock.return_value = 1234567.89
 
         drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
@@ -2574,178 +2579,249 @@ class LibvirtConnTestCase(test.NoDBTestCase,
         test_instance["display_name"] = "purple tomatoes"
         test_instance['system_metadata']['owner_project_name'] = 'sweetshop'
         test_instance['system_metadata']['owner_user_name'] = 'cupcake'
-
-        ctxt = context.RequestContext(project_id=123,
-                                      project_name="aubergine",
-                                      user_id=456,
-                                      user_name="pie")
-
-        flavor = objects.Flavor(name='m1.small',
-                                memory_mb=6,
-                                vcpus=28,
-                                root_gb=496,
-                                ephemeral_gb=8128,
-                                swap=33550336,
-                                extra_specs={})
+        ctxt = context.RequestContext(
+            project_id=123,
+            project_name="aubergine",
+            user_id=456,
+            user_name="pie",
+        )
+        flavor = objects.Flavor(
+            name='m1.small',
+            memory_mb=6,
+            vcpus=28,
+            root_gb=496,
+            ephemeral_gb=8128,
+            swap=33550336,
+            extra_specs={},
+        )
         instance_ref = objects.Instance(**test_instance)
         instance_ref.flavor = flavor
         image_meta = objects.ImageMeta.from_dict(self.test_image_meta)
+        disk_info = blockinfo.get_disk_info(
+            CONF.libvirt.virt_type,
+            instance_ref,
+            image_meta,
+        )
 
-        disk_info = blockinfo.get_disk_info(CONF.libvirt.virt_type,
-                                            instance_ref,
-                                            image_meta)
-
-        cfg = drvr._get_guest_config(instance_ref,
-                                     _fake_network_info(self),
-                                     image_meta, disk_info,
-                                     context=ctxt)
+        cfg = drvr._get_guest_config(
+            instance_ref,
+            _fake_network_info(self),
+            image_meta, disk_info,
+            context=ctxt,
+        )
 
         self.assertEqual(cfg.uuid, instance_ref["uuid"])
-        self.assertEqual(3, len(cfg.features))
-        self.assertIsInstance(cfg.features[0],
-                              vconfig.LibvirtConfigGuestFeatureACPI)
-        self.assertIsInstance(cfg.features[1],
-                              vconfig.LibvirtConfigGuestFeatureAPIC)
-        self.assertIsInstance(
-            cfg.features[2], vconfig.LibvirtConfigGuestFeatureVMCoreInfo)
         self.assertEqual(cfg.memory, 6 * units.Ki)
         self.assertEqual(cfg.vcpus, 28)
         self.assertEqual(cfg.os_type, fields.VMMode.HVM)
         self.assertEqual(cfg.os_boot_dev, ["hd"])
         self.assertIsNone(cfg.os_root)
+
+        self.assertEqual(3, len(cfg.features))
+        for idx, device_type in enumerate([
+            vconfig.LibvirtConfigGuestFeatureACPI,
+            vconfig.LibvirtConfigGuestFeatureAPIC,
+            vconfig.LibvirtConfigGuestFeatureVMCoreInfo,
+        ]):
+            self.assertIsInstance(cfg.features[idx], device_type)
+
         self.assertEqual(len(cfg.devices), 11)
-        self.assertIsInstance(cfg.devices[0],
-                              vconfig.LibvirtConfigGuestDisk)
-        self.assertIsInstance(cfg.devices[1],
-                              vconfig.LibvirtConfigGuestDisk)
-        self.assertIsInstance(cfg.devices[2],
-                              vconfig.LibvirtConfigGuestDisk)
-        self.assertIsInstance(cfg.devices[3],
-                              vconfig.LibvirtConfigGuestInterface)
-        self.assertIsInstance(cfg.devices[4],
-                              vconfig.LibvirtConfigGuestSerial)
-        self.assertIsInstance(cfg.devices[5],
-                              vconfig.LibvirtConfigGuestGraphics)
-        self.assertIsInstance(cfg.devices[6],
-                              vconfig.LibvirtConfigGuestVideo)
-        self.assertIsInstance(cfg.devices[7],
-                              vconfig.LibvirtConfigGuestInput)
-        self.assertIsInstance(cfg.devices[8],
-                              vconfig.LibvirtConfigGuestRng)
-        self.assertIsInstance(cfg.devices[9],
-                              vconfig.LibvirtConfigGuestUSBHostController)
-        self.assertIsInstance(cfg.devices[10],
-                              vconfig.LibvirtConfigMemoryBalloon)
+        for idx, device_type in enumerate([
+            vconfig.LibvirtConfigGuestDisk,
+            vconfig.LibvirtConfigGuestDisk,
+            vconfig.LibvirtConfigGuestDisk,
+            vconfig.LibvirtConfigGuestInterface,
+            vconfig.LibvirtConfigGuestSerial,
+            vconfig.LibvirtConfigGuestGraphics,
+            vconfig.LibvirtConfigGuestVideo,
+            vconfig.LibvirtConfigGuestInput,
+            vconfig.LibvirtConfigGuestRng,
+            vconfig.LibvirtConfigGuestUSBHostController,
+            vconfig.LibvirtConfigMemoryBalloon,
+        ]):
+            self.assertIsInstance(cfg.devices[idx], device_type)
+
         self.assertEqual(len(cfg.metadata), 1)
-        self.assertIsInstance(cfg.metadata[0],
-                              vconfig.LibvirtConfigGuestMetaNovaInstance)
-        self.assertEqual(version.version_string_with_package(),
-                         cfg.metadata[0].package)
-        self.assertEqual("purple tomatoes",
-                         cfg.metadata[0].name)
-        self.assertEqual(1234567.89,
-                         cfg.metadata[0].creationTime)
-        self.assertEqual("image",
-                         cfg.metadata[0].roottype)
-        self.assertEqual(str(instance_ref["image_ref"]),
-                         cfg.metadata[0].rootid)
-
-        self.assertIsInstance(cfg.metadata[0].owner,
-                              vconfig.LibvirtConfigGuestMetaNovaOwner)
-        self.assertEqual("838a72b0-0d54-4827-8fd6-fb1227633ceb",
-                         cfg.metadata[0].owner.userid)
-        self.assertEqual("cupcake",
-                         cfg.metadata[0].owner.username)
-        self.assertEqual("fake",
-                         cfg.metadata[0].owner.projectid)
-        self.assertEqual("sweetshop",
-                         cfg.metadata[0].owner.projectname)
+        self.assertIsInstance(
+            cfg.metadata[0], vconfig.LibvirtConfigGuestMetaNovaInstance)
+        self.assertEqual(
+            version.version_string_with_package(), cfg.metadata[0].package)
+        self.assertEqual("purple tomatoes", cfg.metadata[0].name)
+        self.assertEqual(1234567.89, cfg.metadata[0].creationTime)
+        self.assertEqual("image", cfg.metadata[0].roottype)
+        self.assertEqual(
+            str(instance_ref["image_ref"]), cfg.metadata[0].rootid)
 
-        self.assertIsInstance(cfg.metadata[0].flavor,
-                              vconfig.LibvirtConfigGuestMetaNovaFlavor)
-        self.assertEqual("m1.small",
-                         cfg.metadata[0].flavor.name)
-        self.assertEqual(6,
-                         cfg.metadata[0].flavor.memory)
-        self.assertEqual(28,
-                         cfg.metadata[0].flavor.vcpus)
-        self.assertEqual(496,
-                         cfg.metadata[0].flavor.disk)
-        self.assertEqual(8128,
-                         cfg.metadata[0].flavor.ephemeral)
-        self.assertEqual(33550336,
-                         cfg.metadata[0].flavor.swap)
+        self.assertIsInstance(
+            cfg.metadata[0].owner, vconfig.LibvirtConfigGuestMetaNovaOwner)
+        self.assertEqual(
+            "838a72b0-0d54-4827-8fd6-fb1227633ceb",
+            cfg.metadata[0].owner.userid)
+        self.assertEqual("cupcake", cfg.metadata[0].owner.username)
+        self.assertEqual("fake", cfg.metadata[0].owner.projectid)
+        self.assertEqual("sweetshop", cfg.metadata[0].owner.projectname)
+        self.assertIsInstance(
+            cfg.metadata[0].flavor, vconfig.LibvirtConfigGuestMetaNovaFlavor)
+        self.assertEqual("m1.small", cfg.metadata[0].flavor.name)
+        self.assertEqual(6, cfg.metadata[0].flavor.memory)
+        self.assertEqual(28, cfg.metadata[0].flavor.vcpus)
+        self.assertEqual(496, cfg.metadata[0].flavor.disk)
+        self.assertEqual(8128, cfg.metadata[0].flavor.ephemeral)
+        self.assertEqual(33550336, cfg.metadata[0].flavor.swap)
 
-    @mock.patch.object(host.Host, "_check_machine_type", new=mock.Mock())
-    def test_get_guest_config_q35(self):
-        self.flags(virt_type="kvm",
-                   group='libvirt')
+        num_ports = 0
+        for device in cfg.devices:
+            try:
+                if (
+                    device.root_name == 'controller' and
+                    device.model == 'pcie-root-port'
+                ):
+                    num_ports += 1
+            except AttributeError:
+                pass
 
-        TEST_AMOUNT_OF_PCIE_SLOTS = 8
-        CONF.set_override("num_pcie_ports", TEST_AMOUNT_OF_PCIE_SLOTS,
-                group='libvirt')
+        # i440fx is not pcie machine so there should be no pcie ports
+        self.assertEqual(0, num_ports)
+
+    @mock.patch.object(time, "time")
+    def test_get_guest_config_no_pcie_ports(self, time_mock):
+        """Generate a "standard" guest with minimal configuration.
+
+        This uses i440fx by default since that's our default machine type and
+        x86 is our default architecture (in our test env, anyway).
+        """
+        time_mock.return_value = 1234567.89
 
         drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
-        instance_ref = objects.Instance(**self.test_instance)
-        image_meta = objects.ImageMeta.from_dict({
-            "disk_format": "raw",
-            "properties": {"hw_machine_type":
-                           "pc-q35-test"}})
 
-        disk_info = blockinfo.get_disk_info(CONF.libvirt.virt_type,
-                                            instance_ref,
-                                            image_meta)
+        test_instance = copy.deepcopy(self.test_instance)
+        test_instance["display_name"] = "purple tomatoes"
+        test_instance['system_metadata']['owner_project_name'] = 'sweetshop'
+        test_instance['system_metadata']['owner_user_name'] = 'cupcake'
+        ctxt = context.RequestContext(
+            project_id=123,
+            project_name="aubergine",
+            user_id=456,
+            user_name="pie",
+        )
+        flavor = objects.Flavor(
+            name='m1.small',
+            memory_mb=6,
+            vcpus=28,
+            root_gb=496,
+            ephemeral_gb=8128,
+            swap=33550336,
+            extra_specs={},
+        )
+        instance_ref = objects.Instance(**test_instance)
+        instance_ref.flavor = flavor
+        image_meta = objects.ImageMeta.from_dict(self.test_image_meta)
+        disk_info = blockinfo.get_disk_info(
+            CONF.libvirt.virt_type,
+            instance_ref,
+            image_meta,
+        )
 
-        cfg = drvr._get_guest_config(instance_ref,
-                                     _fake_network_info(self),
-                                     image_meta, disk_info)
+        cfg = drvr._get_guest_config(
+            instance_ref,
+            _fake_network_info(self),
+            image_meta, disk_info,
+            context=ctxt,
+        )
 
         num_ports = 0
         for device in cfg.devices:
             try:
-                if (device.root_name == 'controller' and
-                        device.model == 'pcie-root-port'):
+                if (
+                    device.root_name == 'controller' and
+                    device.model == 'pcie-root-port'
+                ):
                     num_ports += 1
             except AttributeError:
                 pass
 
-        self.assertEqual(TEST_AMOUNT_OF_PCIE_SLOTS, num_ports)
+        # i440fx is not pcie machine so there should be no pcie ports
+        self.assertEqual(0, num_ports)
 
     @mock.patch.object(host.Host, "_check_machine_type", new=mock.Mock())
-    def test_get_guest_config_pcie_i440fx(self):
-        self.flags(virt_type="kvm",
-                   group='libvirt')
+    def test_get_guest_config_q35(self):
+        """Generate a "q35" guest with minimal configuration.
+
+        This configures an explicit machine type (q35) but defaults to x86
+        since this is our default architecture (in our test env, anyway).
+        """
+        self.flags(virt_type="kvm", group='libvirt')
 
         TEST_AMOUNT_OF_PCIE_SLOTS = 8
-        CONF.set_override("num_pcie_ports", TEST_AMOUNT_OF_PCIE_SLOTS,
-                group='libvirt')
+        CONF.set_override(
+            "num_pcie_ports", TEST_AMOUNT_OF_PCIE_SLOTS,
+            group='libvirt',
+        )
 
         drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
         instance_ref = objects.Instance(**self.test_instance)
         image_meta = objects.ImageMeta.from_dict({
             "disk_format": "raw",
-            "properties": {"hw_machine_type":
-                           "pc-i440fx-test"}})
+            "properties": {"hw_machine_type": "q35"},
+        })
 
-        disk_info = blockinfo.get_disk_info(CONF.libvirt.virt_type,
-                                            instance_ref,
-                                            image_meta)
+        disk_info = blockinfo.get_disk_info(
+            CONF.libvirt.virt_type,
+            instance_ref,
+            image_meta,
+        )
 
-        cfg = drvr._get_guest_config(instance_ref,
-                                     _fake_network_info(self),
-                                     image_meta, disk_info)
+        cfg = drvr._get_guest_config(
+            instance_ref,
+            _fake_network_info(self),
+            image_meta,
+            disk_info,
+        )
+
+        self.assertEqual(3, len(cfg.features))
+        for idx, device_type in enumerate([
+            vconfig.LibvirtConfigGuestFeatureACPI,
+            vconfig.LibvirtConfigGuestFeatureAPIC,
+            vconfig.LibvirtConfigGuestFeatureVMCoreInfo,
+        ]):
+            self.assertIsInstance(cfg.features[idx], device_type)
+
+        self.assertEqual(len(cfg.devices), 19)
+        for idx, device_type in enumerate([
+            vconfig.LibvirtConfigGuestDisk,
+            vconfig.LibvirtConfigGuestDisk,
+            vconfig.LibvirtConfigGuestInterface,
+            vconfig.LibvirtConfigGuestSerial,
+            vconfig.LibvirtConfigGuestGraphics,
+            vconfig.LibvirtConfigGuestVideo,
+            vconfig.LibvirtConfigGuestInput,
+            vconfig.LibvirtConfigGuestRng,
+            vconfig.LibvirtConfigGuestPCIeRootController,
+            vconfig.LibvirtConfigGuestPCIeRootPortController,
+            vconfig.LibvirtConfigGuestPCIeRootPortController,
+            vconfig.LibvirtConfigGuestPCIeRootPortController,
+            vconfig.LibvirtConfigGuestPCIeRootPortController,
+            vconfig.LibvirtConfigGuestPCIeRootPortController,
+            vconfig.LibvirtConfigGuestPCIeRootPortController,
+            vconfig.LibvirtConfigGuestPCIeRootPortController,
+            vconfig.LibvirtConfigGuestPCIeRootPortController,
+            vconfig.LibvirtConfigGuestUSBHostController,
+            vconfig.LibvirtConfigMemoryBalloon,
+        ]):
+            self.assertIsInstance(cfg.devices[idx], device_type)
 
         num_ports = 0
         for device in cfg.devices:
             try:
-                if (device.root_name == 'controller' and
-                        device.model == 'pcie-root-port'):
+                if (
+                    device.root_name == 'controller' and
+                    device.model == 'pcie-root-port'
+                ):
                     num_ports += 1
             except AttributeError:
                 pass
 
-        # i440fx is not pcie machine so there should be no pcie ports
-        self.assertEqual(0, num_ports)
+        self.assertEqual(TEST_AMOUNT_OF_PCIE_SLOTS, num_ports)
 
     @mock.patch.object(host.Host, "_check_machine_type", new=mock.Mock())
     @mock.patch('nova.virt.libvirt.utils.get_default_machine_type',
@@ -8436,6 +8512,206 @@ class LibvirtConnTestCase(test.NoDBTestCase,
         self.assertEqual(conf.cpu.cores, 2)
         self.assertEqual(conf.cpu.threads, 1)
 
+    def test_get_guest_iommu_not_enabled(self):
+        drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
+
+        test_instance = _create_test_instance()
+        instance_ref = objects.Instance(**test_instance)
+        image_meta = objects.ImageMeta.from_dict(self.test_image_meta)
+        disk_info = blockinfo.get_disk_info(CONF.libvirt.virt_type,
+                                            instance_ref,
+                                            image_meta)
+
+        cfg = drvr._get_guest_config(instance_ref, [],
+                                     image_meta, disk_info)
+        for device in cfg.devices:
+            self.assertNotEqual('iommu', device.root_name)
+
+    def test_get_guest_iommu_config_model(self):
+        drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
+        image_meta = objects.ImageMeta.from_dict({
+            "disk_format": "raw",
+            "properties": {"hw_machine_type": "q35"},
+        })
+
+        extra_specs = {
+            "hw:viommu_model": 'intel',
+        }
+        test_instance = _create_test_instance()
+        test_instance["flavor"]["extra_specs"] = extra_specs
+        instance_ref = objects.Instance(**test_instance)
+        disk_info = blockinfo.get_disk_info(CONF.libvirt.virt_type,
+                                            instance_ref,
+                                            image_meta)
+
+        cfg = drvr._get_guest_config(instance_ref, [],
+                                     image_meta, disk_info)
+        count = 0
+        for device in cfg.devices:
+            if device.root_name == 'iommu':
+                count += 1
+                self.assertIsInstance(device,
+                                      vconfig.LibvirtConfigGuestIOMMU)
+                self.assertEqual('intel', device.model)
+                self.assertFalse(hasattr(device, "aw_bits"))
+                self.assertTrue(device.interrupt_remapping)
+                self.assertTrue(device.caching_mode)
+                self.assertTrue(device.eim)
+                self.assertTrue(device.iotlb)
+
+        self.assertEqual(1, count)
+        self.assertEqual('q35', cfg.os_mach_type)
+
+    @mock.patch.object(host.Host, 'has_min_version', return_value=True)
+    def test_get_guest_iommu_config_model_auto(self, has_min_version):
+        drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
+        image_meta = objects.ImageMeta.from_dict({
+            "disk_format": "raw",
+            "properties": {"hw_machine_type": "q35"},
+        })
+
+        extra_specs = {
+            "hw:viommu_model": 'auto',
+        }
+        test_instance = _create_test_instance()
+        test_instance["flavor"]["extra_specs"] = extra_specs
+        instance_ref = objects.Instance(**test_instance)
+        disk_info = blockinfo.get_disk_info(CONF.libvirt.virt_type,
+                                            instance_ref,
+                                            image_meta)
+
+        cfg = drvr._get_guest_config(instance_ref, [],
+                                     image_meta, disk_info)
+        count = 0
+        for device in cfg.devices:
+            if device.root_name == 'iommu':
+                count += 1
+                self.assertIsInstance(device,
+                                      vconfig.LibvirtConfigGuestIOMMU)
+                self.assertEqual('virtio', device.model)
+                self.assertEqual(48, device.aw_bits)
+                self.assertTrue(device.interrupt_remapping)
+                self.assertTrue(device.caching_mode)
+                self.assertTrue(device.eim)
+                self.assertTrue(device.iotlb)
+
+        self.assertEqual(1, count)
+        self.assertEqual('q35', cfg.os_mach_type)
+
+    @mock.patch.object(host.Host, 'has_min_version', return_value=False)
+    def test_get_guest_iommu_config_model_auto_intel(self, has_min_version):
+        drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
+        image_meta = objects.ImageMeta.from_dict({
+            "disk_format": "raw",
+            "properties": {"hw_machine_type": "q35"},
+        })
+
+        extra_specs = {
+            "hw:viommu_model": 'auto',
+        }
+        test_instance = _create_test_instance()
+        test_instance["flavor"]["extra_specs"] = extra_specs
+        instance_ref = objects.Instance(**test_instance)
+        disk_info = blockinfo.get_disk_info(CONF.libvirt.virt_type,
+                                            instance_ref,
+                                            image_meta)
+
+        cfg = drvr._get_guest_config(instance_ref, [],
+                                     image_meta, disk_info)
+        count = 0
+        for device in cfg.devices:
+            if device.root_name == 'iommu':
+                count += 1
+                self.assertIsInstance(device,
+                                      vconfig.LibvirtConfigGuestIOMMU)
+                self.assertEqual('intel', device.model)
+                self.assertTrue(device.interrupt_remapping)
+                self.assertTrue(device.caching_mode)
+                self.assertTrue(device.eim)
+                self.assertTrue(device.iotlb)
+
+        self.assertEqual(1, count)
+        self.assertEqual('q35', cfg.os_mach_type)
+
+    @mock.patch.object(host.Host, 'has_min_version', return_value=False)
+    def test_get_guest_iommu_config_model_auto_aarch64(self, has_min_version):
+        drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
+
+        image_meta = objects.ImageMeta.from_dict({
+            "disk_format": "raw",
+            "properties": {"hw_viommu_model": 'auto',
+                           "hw_architecture": fields.Architecture.AARCH64,
+                           "hw_machine_type": "virt"},
+        })
+        extra_specs = {
+            "hw:viommu_model": 'auto',
+        }
+        test_instance = _create_test_instance()
+        test_instance["flavor"]["extra_specs"] = extra_specs
+        instance_ref = objects.Instance(**test_instance)
+        disk_info = blockinfo.get_disk_info(CONF.libvirt.virt_type,
+                                            instance_ref,
+                                            image_meta)
+
+        cfg = drvr._get_guest_config(instance_ref, [],
+                                     image_meta, disk_info)
+        count = 0
+        for device in cfg.devices:
+            if device.root_name == 'iommu':
+                count += 1
+                self.assertIsInstance(device,
+                                      vconfig.LibvirtConfigGuestIOMMU)
+                self.assertEqual('smmuv3', device.model)
+                self.assertFalse(hasattr(device, "aw_bits"))
+                self.assertTrue(device.interrupt_remapping)
+                self.assertTrue(device.caching_mode)
+                self.assertFalse(device.eim)
+                self.assertTrue(device.iotlb)
+        self.assertEqual(1, count)
+
+    def test_get_guest_iommu_config_not_support_machine_type(self):
+        drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
+        image_meta = objects.ImageMeta.from_dict({
+            "disk_format": "raw",
+            "properties": {"hw_machine_type": "pc-i440fx-2.11"},
+        })
+        extra_specs = {
+            "hw:viommu_model": 'auto',
+        }
+        test_instance = _create_test_instance()
+        test_instance["flavor"]["extra_specs"] = extra_specs
+        instance_ref = objects.Instance(**test_instance)
+        disk_info = blockinfo.get_disk_info(CONF.libvirt.virt_type,
+                                            instance_ref,
+                                            image_meta)
+
+        self.assertRaises(
+            exception.InvalidVIOMMUMachineType, drvr._get_guest_config,
+            instance_ref, [], image_meta, disk_info
+        )
+
+    def test_get_guest_iommu_config_not_support_architecture(self):
+        drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
+        image_meta = objects.ImageMeta.from_dict({
+            "disk_format": "raw",
+            "properties": {"hw_architecture": fields.Architecture.PPC64LE,
+                           "hw_machine_type": "pc-i440fx-2.11"},
+        })
+        extra_specs = {
+            "hw:viommu_model": 'auto',
+        }
+        test_instance = _create_test_instance()
+        test_instance["flavor"]["extra_specs"] = extra_specs
+        instance_ref = objects.Instance(**test_instance)
+        disk_info = blockinfo.get_disk_info(CONF.libvirt.virt_type,
+                                            instance_ref,
+                                            image_meta)
+
+        self.assertRaises(
+            exception.InvalidVIOMMUArchitecture, drvr._get_guest_config,
+            instance_ref, [], image_meta, disk_info
+        )
+
     def test_get_guest_memory_balloon_config_by_default(self):
         drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
         instance_ref = objects.Instance(**self.test_instance)
diff --git a/nova/virt/libvirt/config.py b/nova/virt/libvirt/config.py
index 07f22c9b91..3d91c325c3 100644
--- a/nova/virt/libvirt/config.py
+++ b/nova/virt/libvirt/config.py
@@ -24,6 +24,7 @@ helpers for populating up config object instances.
 """
 
 import time
+import typing as ty
 
 from collections import OrderedDict
 from lxml import etree
@@ -32,6 +33,7 @@ from oslo_utils import units
 
 from nova import exception
 from nova.i18n import _
+from nova.objects import fields
 from nova.pci import utils as pci_utils
 from nova.virt import hardware
 
@@ -66,9 +68,6 @@ class LibvirtConfigObject(object):
             child.text = str(value)
         return child
 
-    def get_yes_no_str(self, value):
-        return 'yes' if value else 'no'
-
     def format_dom(self):
         return self._new_node(self.root_name)
 
@@ -87,6 +86,25 @@ class LibvirtConfigObject(object):
                                  pretty_print=pretty_print)
         return xml_str
 
+    @classmethod
+    def parse_on_off_str(self, value: ty.Optional[str]) -> bool:
+        if value is not None and value not in ('on', 'off'):
+            msg = _(
+                "Element should contain either 'on' or 'off'; "
+                "found: '%(value)s'"
+            )
+            raise exception.InvalidInput(msg % {'value': value})
+
+        return value == 'on'
+
+    @classmethod
+    def get_yes_no_str(self, value: bool) -> str:
+        return 'yes' if value else 'no'
+
+    @classmethod
+    def get_on_off_str(self, value: bool) -> str:
+        return 'on' if value else 'off'
+
     def __repr__(self):
         return self.to_xml(pretty_print=False)
 
@@ -2735,6 +2753,18 @@ class LibvirtConfigGuestFeaturePMU(LibvirtConfigGuestFeature):
         return root
 
 
+class LibvirtConfigGuestFeatureIOAPIC(LibvirtConfigGuestFeature):
+
+    def __init__(self, **kwargs):
+        super().__init__("ioapic", **kwargs)
+        self.driver = "qemu"
+
+    def format_dom(self):
+        root = super().format_dom()
+        root.set('driver', self.driver)
+        return root
+
+
 class LibvirtConfigGuestFeatureHyperV(LibvirtConfigGuestFeature):
 
     # QEMU requires at least this value to be set
@@ -3090,6 +3120,7 @@ class LibvirtConfigGuest(LibvirtConfigObject):
         #                            LibvirtConfigGuestGidMap
         #                            LibvirtConfigGuestCPU
         #                            LibvirtConfigGuestVPMEM
+        #                            LibvirtConfigGuestIOMMU
         for c in xmldoc:
             if c.tag == 'devices':
                 for d in c:
@@ -3117,6 +3148,10 @@ class LibvirtConfigGuest(LibvirtConfigObject):
                         obj = LibvirtConfigGuestVPMEM()
                         obj.parse_dom(d)
                         self.devices.append(obj)
+                    elif d.tag == 'iommu':
+                        obj = LibvirtConfigGuestIOMMU()
+                        obj.parse_dom(d)
+                        self.devices.append(obj)
             if c.tag == 'idmap':
                 for idmap in c:
                     obj = None
@@ -3141,7 +3176,10 @@ class LibvirtConfigGuest(LibvirtConfigObject):
             else:
                 self._parse_basic_props(c)
 
-    def add_device(self, dev):
+    def add_feature(self, dev: LibvirtConfigGuestFeature) -> None:
+        self.features.append(dev)
+
+    def add_device(self, dev: LibvirtConfigGuestDevice) -> None:
         self.devices.append(dev)
 
     def add_perf_event(self, event):
@@ -3680,6 +3718,53 @@ class LibvirtConfigGuestVPMEM(LibvirtConfigGuestDevice):
                         self.target_size = sub.text
 
 
+class LibvirtConfigGuestIOMMU(LibvirtConfigGuestDevice):
+    """https://libvirt.org/formatdomain.html#iommu-devices"""
+
+    def __init__(self, **kwargs):
+        super().__init__(root_name="iommu", **kwargs)
+
+        self.model: str = fields.VIOMMUModel.AUTO
+        self.interrupt_remapping: bool = False
+        self.caching_mode: bool = False
+        self.eim: bool = False
+        self.iotlb: bool = False
+
+    def format_dom(self):
+        iommu = super().format_dom()
+        iommu.set("model", self.model)
+
+        driver = etree.Element("driver")
+        driver.set("intremap", self.get_on_off_str(self.interrupt_remapping))
+        driver.set("caching_mode", self.get_on_off_str(self.caching_mode))
+
+        # Set aw_bits to None when the Libvirt version not satisfy
+        # MIN_LIBVIRT_VIOMMU_AW_BITS in driver. When it's None, means it's not
+        # supported to have aw_bits.
+        if hasattr(self, "aw_bits"):
+            driver.set("aw_bits", str(self.aw_bits))
+        driver.set("eim", self.get_on_off_str(self.eim))
+        driver.set("iotlb", self.get_on_off_str(self.iotlb))
+        iommu.append(driver)
+
+        return iommu
+
+    def parse_dom(self, xmldoc):
+        super().parse_dom(xmldoc)
+        self.model = xmldoc.get("model")
+
+        driver = xmldoc.find("./driver")
+        if driver:
+            self.interrupt_remapping = self.parse_on_off_str(
+                driver.get("intremap"))
+            self.caching_mode = self.parse_on_off_str(
+                driver.get("caching_mode"))
+            if driver.get("aw_bits") is not None:
+                self.aw_bits = int(driver.get("aw_bits"))
+            self.iotlb = self.parse_on_off_str(driver.get("iotlb"))
+            self.eim = self.parse_on_off_str(driver.get("eim"))
+
+
 class LibvirtConfigGuestMetaNovaPorts(LibvirtConfigObject):
 
     def __init__(self, ports=None):
diff --git a/nova/virt/libvirt/driver.py b/nova/virt/libvirt/driver.py
index 925c98aa88..cf3c4464e8 100644
--- a/nova/virt/libvirt/driver.py
+++ b/nova/virt/libvirt/driver.py
@@ -221,6 +221,12 @@ MIN_QEMU_VERSION = (4, 2, 0)
 NEXT_MIN_LIBVIRT_VERSION = (7, 0, 0)
 NEXT_MIN_QEMU_VERSION = (5, 2, 0)
 
+# vIOMMU driver attribute aw_bits minimal support version.
+MIN_LIBVIRT_VIOMMU_AW_BITS = (6, 5, 0)
+
+# vIOMMU model value `virtio` minimal support version
+MIN_LIBVIRT_VIOMMU_VIRTIO_MODEL = (8, 3, 0)
+
 MIN_LIBVIRT_AARCH64_CPU_COMPARE = (6, 9, 0)
 
 # Virtuozzo driver support
@@ -6134,9 +6140,9 @@ class LibvirtDriver(driver.ComputeDriver):
                 image_meta.properties.get('img_hide_hypervisor_id'))
 
         if CONF.libvirt.virt_type in ('qemu', 'kvm'):
-            guest.features.append(vconfig.LibvirtConfigGuestFeatureACPI())
+            guest.add_feature(vconfig.LibvirtConfigGuestFeatureACPI())
             if not CONF.workarounds.libvirt_disable_apic:
-                guest.features.append(vconfig.LibvirtConfigGuestFeatureAPIC())
+                guest.add_feature(vconfig.LibvirtConfigGuestFeatureAPIC())
 
         if CONF.libvirt.virt_type in ('qemu', 'kvm') and os_type == 'windows':
             hv = vconfig.LibvirtConfigGuestFeatureHyperV()
@@ -6180,16 +6186,16 @@ class LibvirtDriver(driver.ComputeDriver):
                 fields.Architecture.I686, fields.Architecture.X86_64,
                 fields.Architecture.AARCH64,
             ):
-                guest.features.append(
+                guest.add_feature(
                     vconfig.LibvirtConfigGuestFeatureVMCoreInfo())
 
             if hide_hypervisor_id:
-                guest.features.append(
+                guest.add_feature(
                     vconfig.LibvirtConfigGuestFeatureKvmHidden())
 
             pmu = hardware.get_pmu_constraint(flavor, image_meta)
             if pmu is not None:
-                guest.features.append(
+                guest.add_feature(
                     vconfig.LibvirtConfigGuestFeaturePMU(pmu))
 
     def _check_number_of_serial_console(self, num_ports):
@@ -6671,18 +6677,26 @@ class LibvirtDriver(driver.ComputeDriver):
                 self._create_consoles_qemu_kvm(
                     guest_cfg, instance, flavor, image_meta)
 
-    def _is_mipsel_guest(self, image_meta):
+    def _is_mipsel_guest(self, image_meta: 'objects.ImageMeta') -> bool:
         archs = (fields.Architecture.MIPSEL, fields.Architecture.MIPS64EL)
         return self._check_emulation_arch(image_meta) in archs
 
-    def _is_s390x_guest(self, image_meta):
+    def _is_s390x_guest(self, image_meta: 'objects.ImageMeta') -> bool:
         archs = (fields.Architecture.S390, fields.Architecture.S390X)
         return self._check_emulation_arch(image_meta) in archs
 
-    def _is_ppc64_guest(self, image_meta):
+    def _is_ppc64_guest(self, image_meta: 'objects.ImageMeta') -> bool:
         archs = (fields.Architecture.PPC64, fields.Architecture.PPC64LE)
         return self._check_emulation_arch(image_meta) in archs
 
+    def _is_aarch64_guest(self, image_meta: 'objects.ImageMeta') -> bool:
+        arch = fields.Architecture.AARCH64
+        return self._check_emulation_arch(image_meta) == arch
+
+    def _is_x86_guest(self, image_meta: 'objects.ImageMeta') -> bool:
+        archs = (fields.Architecture.I686, fields.Architecture.X86_64)
+        return self._check_emulation_arch(image_meta) in archs
+
     def _create_consoles_qemu_kvm(self, guest_cfg, instance, flavor,
                                   image_meta):
         char_dev_cls = vconfig.LibvirtConfigGuestSerial
@@ -7060,6 +7074,8 @@ class LibvirtDriver(driver.ComputeDriver):
         if vpmems:
             self._guest_add_vpmems(guest, vpmems)
 
+        self._guest_add_iommu_device(guest, image_meta, flavor)
+
         return guest
 
     def _get_ordered_vpmems(self, instance, flavor):
@@ -7365,6 +7381,92 @@ class LibvirtDriver(driver.ComputeDriver):
         # returned for unit testing purposes
         return keyboard
 
+    def _get_iommu_model(
+        self,
+        guest: vconfig.LibvirtConfigGuest,
+        image_meta: 'objects.ImageMeta',
+        flavor: 'objects.Flavor',
+    ) -> ty.Optional[str]:
+        model = flavor.extra_specs.get(
+            'hw:viommu_model') or image_meta.properties.get(
+                'hw_viommu_model')
+        if not model:
+            return None
+
+        is_x86 = self._is_x86_guest(image_meta)
+        is_aarch64 = self._is_aarch64_guest(image_meta)
+
+        if is_x86:
+            if guest.os_mach_type is not None and not (
+                    'q35' in guest.os_mach_type
+            ):
+                arch = self._check_emulation_arch(image_meta)
+                mtype = guest.os_mach_type if (
+                    guest.os_mach_type is not None
+                ) else "unknown"
+                raise exception.InvalidVIOMMUMachineType(
+                    mtype=mtype, arch=arch)
+        elif is_aarch64:
+            if guest.os_mach_type is not None and not (
+                    'virt' in guest.os_mach_type
+            ):
+                arch = self._check_emulation_arch(image_meta)
+                mtype = guest.os_mach_type if (
+                    guest.os_mach_type is not None
+                ) else "unknown"
+                raise exception.InvalidVIOMMUMachineType(
+                    mtype=mtype, arch=arch)
+        else:
+            raise exception.InvalidVIOMMUArchitecture(
+                arch=self._check_emulation_arch(image_meta))
+
+        if model == fields.VIOMMUModel.AUTO:
+            if self._host.has_min_version(MIN_LIBVIRT_VIOMMU_VIRTIO_MODEL):
+                model = fields.VIOMMUModel.VIRTIO
+            elif self._is_x86_guest(image_meta) and (
+                guest.os_mach_type is not None and 'q35' in guest.os_mach_type
+            ):
+                model = fields.VIOMMUModel.INTEL
+            else:
+                # AArch64
+                model = fields.VIOMMUModel.SMMUV3
+        return model
+
+    def _guest_add_iommu_device(
+        self,
+        guest: vconfig.LibvirtConfigGuest,
+        image_meta: 'objects.ImageMeta',
+        flavor: 'objects.Flavor',
+    ) -> None:
+        """Add a virtual IOMMU device to allow e.g. vfio-pci usage."""
+        if CONF.libvirt.virt_type not in ('qemu', 'kvm'):
+            # vIOMMU requires QEMU
+            return
+
+        iommu = vconfig.LibvirtConfigGuestIOMMU()
+
+        iommu.model = self._get_iommu_model(guest, image_meta, flavor)
+        if iommu.model is None:
+            return
+
+        iommu.interrupt_remapping = True
+        iommu.caching_mode = True
+        iommu.iotlb = True
+
+        # As Qemu supported values are 39 and 48, we set this to
+        # larger width (48) by default and will not exposed to end user.
+        if self._host.has_min_version(MIN_LIBVIRT_VIOMMU_AW_BITS):
+            iommu.aw_bits = 48
+
+        if guest.os_mach_type is not None and 'q35' in guest.os_mach_type:
+            iommu.eim = True
+        else:
+            iommu.eim = False
+        guest.add_device(iommu)
+
+        ioapic = vconfig.LibvirtConfigGuestFeatureIOAPIC()
+        guest.add_feature(ioapic)
+
     def _get_guest_xml(self, context, instance, network_info, disk_info,
                        image_meta, rescue=None,
                        block_device_info=None,
diff --git a/releasenotes/notes/guest-iommu-device-4795c3a060aca424.yaml b/releasenotes/notes/guest-iommu-device-4795c3a060aca424.yaml
new file mode 100644
index 0000000000..314c2c0ffe
--- /dev/null
+++ b/releasenotes/notes/guest-iommu-device-4795c3a060aca424.yaml
@@ -0,0 +1,21 @@
+---
+features:
+  - |
+    The Libvirt driver can now add a virtual IOMMU device
+    to all created guests, when running on an x86 host and using the Q35
+    machine type or on AArch64.
+
+    To enable this, provide `hw:viommu_model` in flavor extra
+    spec or equivalent image metadata property `hw_viommu_model` and with the
+    guest CPU architecture and OS allows, we will enable viommu in Libvirt
+    driver. Support values intel|smmuv3|virtio|auto. Default to ``auto``.
+    Which ``auto`` will automatically select ``virtio`` if Libvirt supports it,
+    else ``intel`` on X86 (Q35) and ``smmuv3`` on AArch64.
+    vIOMMU config will raise invalid exception if the guest architecture is
+    neither X86 (Q35) or AArch64.
+
+    Note that, enable vIOMMU might introduce significant performance overhead.
+    You can see performance comparision table from
+    `AMD vIOMMU session on KVM Forum 2021`_.
+    For above reason, vIOMMU should only be enable for workflow that require it.
+    .. _`AMD vIOMMU session on KVM Forum 2021`: https://static.sched.com/hosted_files/kvmforum2021/da/vIOMMU%20KVM%20Forum%202021%20-%20v4.pdf