diff --git a/nova/tests/test_libvirt.py b/nova/tests/test_libvirt.py
index f93c724b..9fb739a5 100644
--- a/nova/tests/test_libvirt.py
+++ b/nova/tests/test_libvirt.py
@@ -32,6 +32,7 @@ from nova.compute import instance_types
 from nova.compute import power_state
 from nova.compute import rpcapi as compute_rpcapi
 from nova.compute import utils as compute_utils
+from nova.compute import vm_mode
 from nova.compute import vm_states
 from nova import context
 from nova import db
@@ -508,7 +509,7 @@ class LibvirtConnTestCase(test.TestCase):
         self.assertEquals(cfg.acpi, True)
         self.assertEquals(cfg.memory, 1024 * 1024 * 2)
         self.assertEquals(cfg.vcpus, 1)
-        self.assertEquals(cfg.os_type, "hvm")
+        self.assertEquals(cfg.os_type, vm_mode.HVM)
         self.assertEquals(cfg.os_boot_dev, "hd")
         self.assertEquals(cfg.os_root, None)
         self.assertEquals(len(cfg.devices), 7)
@@ -552,7 +553,7 @@ class LibvirtConnTestCase(test.TestCase):
         self.assertEquals(cfg.acpi, True)
         self.assertEquals(cfg.memory, 1024 * 1024 * 2)
         self.assertEquals(cfg.vcpus, 1)
-        self.assertEquals(cfg.os_type, "hvm")
+        self.assertEquals(cfg.os_type, vm_mode.HVM)
         self.assertEquals(cfg.os_boot_dev, "hd")
         self.assertEquals(cfg.os_root, None)
         self.assertEquals(len(cfg.devices), 8)
@@ -1363,18 +1364,22 @@ class LibvirtConnTestCase(test.TestCase):
 
         type_uri_map = {'qemu': ('qemu:///system',
                              [(lambda t: t.find('.').get('type'), 'qemu'),
-                              (lambda t: t.find('./os/type').text, 'hvm'),
+                              (lambda t: t.find('./os/type').text,
+                               vm_mode.HVM),
                               (lambda t: t.find('./devices/emulator'), None)]),
                         'kvm': ('qemu:///system',
                              [(lambda t: t.find('.').get('type'), 'kvm'),
-                              (lambda t: t.find('./os/type').text, 'hvm'),
+                              (lambda t: t.find('./os/type').text,
+                               vm_mode.HVM),
                               (lambda t: t.find('./devices/emulator'), None)]),
                         'uml': ('uml:///system',
                              [(lambda t: t.find('.').get('type'), 'uml'),
-                              (lambda t: t.find('./os/type').text, 'uml')]),
+                              (lambda t: t.find('./os/type').text,
+                               vm_mode.UML)]),
                         'xen': ('xen:///',
                              [(lambda t: t.find('.').get('type'), 'xen'),
-                              (lambda t: t.find('./os/type').text, 'linux')]),
+                              (lambda t: t.find('./os/type').text,
+                               vm_mode.XEN)]),
                               }
 
         for hypervisor_type in ['qemu', 'kvm', 'xen']:
@@ -2149,12 +2154,12 @@ class LibvirtConnTestCase(test.TestCase):
             caps.host.cpu = cpu
 
             guest = config.LibvirtConfigGuest()
-            guest.ostype = "hvm"
+            guest.ostype = vm_mode.HVM
             guest.arch = "x86_64"
             caps.guests.append(guest)
 
             guest = config.LibvirtConfigGuest()
-            guest.ostype = "hvm"
+            guest.ostype = vm_mode.HVM
             guest.arch = "i686"
             caps.guests.append(guest)
 
diff --git a/nova/tests/test_vmmode.py b/nova/tests/test_vmmode.py
new file mode 100644
index 00000000..cd639478
--- /dev/null
+++ b/nova/tests/test_vmmode.py
@@ -0,0 +1,54 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+#
+#    Copyright (C) 2012 Red Hat, Inc.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from nova import exception
+from nova import test
+
+from nova.compute import vm_mode
+
+
+class ComputeVMModeTest(test.TestCase):
+
+    class testinstance(object):
+        def __init__(self, mode):
+            self.vm_mode = mode
+
+    def test_case(self):
+        inst = ComputeVMModeTest.testinstance("HVM")
+        mode = vm_mode.get_from_instance(inst)
+        self.assertEqual(mode, "hvm")
+
+    def test_legacy_pv(self):
+        inst = ComputeVMModeTest.testinstance("pv")
+        mode = vm_mode.get_from_instance(inst)
+        self.assertEqual(mode, "xen")
+
+    def test_legacy_hv(self):
+        inst = ComputeVMModeTest.testinstance("hv")
+        mode = vm_mode.get_from_instance(inst)
+        self.assertEqual(mode, "hvm")
+
+    def test_bogus(self):
+        inst = ComputeVMModeTest.testinstance("wibble")
+
+        self.assertRaises(exception.Invalid,
+                          vm_mode.get_from_instance,
+                          inst)
+
+    def test_good(self):
+        inst = ComputeVMModeTest.testinstance("hvm")
+        mode = vm_mode.get_from_instance(inst)
+        self.assertEqual(mode, "hvm")
diff --git a/nova/tests/test_xenapi.py b/nova/tests/test_xenapi.py
index 9486f414..b8315a02 100644
--- a/nova/tests/test_xenapi.py
+++ b/nova/tests/test_xenapi.py
@@ -849,6 +849,7 @@ class XenAPIVMTestCase(stubs.XenAPITestBase):
             'root_gb': 20,
             'instance_type_id': '3',  # m1.large
             'os_type': 'linux',
+            'vm_mode': 'hvm',
             'architecture': 'x86-64'}
         instance = db.instance_create(self.context, instance_values)
         network_info = fake_network.fake_get_instance_nw_info(self.stubs,