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>

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()
 

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(),