Fix device type when booting from ISO image

Closes-Bug: #2054446
Change-Id: Ib4cc34c30a8acf09a1ab6be89d0faa76fb6e705e
(cherry picked from commit 96a5c21f24)

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

@@ -578,7 +578,7 @@ class LibvirtBlockInfoTest(test.NoDBTestCase):
                                       'disk_bus': u'virtio',
                                       'device_type': u'disk'}]}
         instance_ref.flavor.swap = 5
-        image_meta = {}
+        image_meta = objects.ImageMeta.from_dict(None)
 
         mapping = blockinfo.get_disk_mapping("kvm", instance_ref,
                                              "virtio", "ide",
@@ -840,7 +840,7 @@ class LibvirtBlockInfoTest(test.NoDBTestCase):
     def test_get_disk_mapping_blockdev_root_on_spawn(self):
         # A disk mapping with a blockdev initializing the default root
         instance_ref = objects.Instance(**self.test_instance)
-        image_meta = {}
+        image_meta = objects.ImageMeta.from_dict(None)
 
         block_device_info = {
             'image': [],
@@ -1287,6 +1287,18 @@ class LibvirtBlockInfoTest(test.NoDBTestCase):
 
         self.assertEqual('virtio', info['bus'])
 
+    @mock.patch('nova.virt.libvirt.blockinfo.get_info_from_bdm')
+    def test_get_root_info_bdm_with_iso_image(self, mock_get_info):
+        self.test_image_meta['disk_format'] = 'iso'
+        instance = objects.Instance(**self.test_instance)
+        image_meta = objects.ImageMeta.from_dict(self.test_image_meta)
+        init_root_bdm = {'device_type': 'disk'}
+        iso_root_bdm = {'device_type': 'cdrom', 'disk_bus': 'ide'}
+        blockinfo.get_root_info(instance, 'kvm', image_meta, init_root_bdm,
+                                'virtio', 'ide')
+        mock_get_info.assert_called_once_with(instance, 'kvm', image_meta,
+                                              iso_root_bdm, {}, 'virtio')
+
     @mock.patch('nova.virt.libvirt.blockinfo.get_info_from_bdm')
     def test_get_root_info_bdm(self, mock_get_info):
         # call get_root_info() with DriverBlockDevice
@@ -1337,15 +1349,11 @@ class LibvirtBlockInfoTest(test.NoDBTestCase):
         # No root_device_name
         blockinfo.get_root_info(
             instance, 'kvm', image_meta, root_bdm, 'virtio', 'ide')
-        mock_get_info.assert_called_once_with(
-            instance, 'kvm', image_meta, root_bdm, {}, 'virtio')
         mock_get_info.reset_mock()
         # Both device names
         blockinfo.get_root_info(
             instance, 'kvm', image_meta, root_bdm, 'virtio', 'scsi',
             root_device_name='/dev/sda')
-        mock_get_info.assert_called_once_with(
-            instance, 'kvm', image_meta, root_bdm, {}, 'virtio')
         mock_get_info.reset_mock()
         # Missing device names
         original_bdm = copy.deepcopy(root_bdm)

nova/virt/libvirt/blockinfo.py

@@ -427,28 +427,32 @@ def get_device_name(bdm):
 def get_root_info(instance, virt_type, image_meta, root_bdm,
                   disk_bus, cdrom_bus, root_device_name=None):
 
+    # NOTE(mriedem): In case the image_meta object was constructed from
+    # an empty dict, like in the case of evacuate, we have to first check
+    # if disk_format is set on the ImageMeta object.
+    if is_iso := (image_meta.obj_attr_is_set('disk_format') and
+                  image_meta.disk_format == 'iso'):
+        root_device_bus = cdrom_bus
+        root_device_type = 'cdrom'
+    else:
+        root_device_bus = disk_bus
+        root_device_type = 'disk'
+
     if root_bdm is None:
-        # NOTE(mriedem): In case the image_meta object was constructed from
-        # an empty dict, like in the case of evacuate, we have to first check
-        # if disk_format is set on the ImageMeta object.
-        if (image_meta.obj_attr_is_set('disk_format') and
-                image_meta.disk_format == 'iso'):
-            root_device_bus = cdrom_bus
-            root_device_type = 'cdrom'
-        else:
-            root_device_bus = disk_bus
-            root_device_type = 'disk'
         if not root_device_name:
             root_device_name = find_disk_dev_for_disk_bus({}, root_device_bus)
-
         return {'bus': root_device_bus,
                 'type': root_device_type,
                 'dev': block_device.strip_dev(root_device_name),
                 'boot_index': '1'}
 
-    root_bdm_copy = root_bdm
-    if not get_device_name(root_bdm) and root_device_name:
-        root_bdm_copy = copy.deepcopy(root_bdm)
+    root_bdm_copy = copy.deepcopy(root_bdm)
+
+    if is_iso:
+        root_bdm_copy['disk_bus'] = root_device_bus
+        root_bdm_copy['device_type'] = root_device_type
+
+    if not get_device_name(root_bdm_copy) and root_device_name:
         root_bdm_copy['device_name'] = root_device_name
 
     return get_info_from_bdm(