Merge "libvirt: move capabilities helper into host.py"

5 files changed, 160 insertions, 157 deletions

diff --git a/nova/tests/unit/virt/libvirt/fakelibvirt.py b/nova/tests/unit/virt/libvirt/fakelibvirt.py
index 1aebc0b49b..10f499f07a 100644
--- a/nova/tests/unit/virt/libvirt/fakelibvirt.py
+++ b/nova/tests/unit/virt/libvirt/fakelibvirt.py
@@ -1050,8 +1050,21 @@ class Connection(object):
     def baselineCPU(self, cpu, flag):
         """Add new libvirt API."""
         return """<cpu mode='custom' match='exact'>
-                    <model fallback='allow'>Westmere</model>
+                    <model>Penryn</model>
                     <vendor>Intel</vendor>
+                    <feature name='xtpr'/>
+                    <feature name='tm2'/>
+                    <feature name='est'/>
+                    <feature name='vmx'/>
+                    <feature name='ds_cpl'/>
+                    <feature name='monitor'/>
+                    <feature name='pbe'/>
+                    <feature name='tm'/>
+                    <feature name='ht'/>
+                    <feature name='ss'/>
+                    <feature name='acpi'/>
+                    <feature name='ds'/>
+                    <feature name='vme'/>
                     <feature policy='require' name='aes'/>
                   </cpu>"""
 
diff --git a/nova/tests/unit/virt/libvirt/test_driver.py b/nova/tests/unit/virt/libvirt/test_driver.py
index cf75814417..31b95fbeeb 100644
--- a/nova/tests/unit/virt/libvirt/test_driver.py
+++ b/nova/tests/unit/virt/libvirt/test_driver.py
@@ -917,8 +917,7 @@ class LibvirtConnTestCase(test.NoDBTestCase):
 
         @mock.patch.object(libvirt, 'registerErrorHandler',
                            side_effect=fake_registerErrorHandler)
-        @mock.patch.object(libvirt_driver.LibvirtDriver,
-                           '_get_host_capabilities',
+        @mock.patch.object(host.Host, "get_capabilities",
                             side_effect=fake_get_host_capabilities)
         def test_init_host(get_host_capabilities, register_error_handler):
             conn = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
@@ -958,89 +957,6 @@ class LibvirtConnTestCase(test.NoDBTestCase):
             # our stub method is called which asserts the password is scrubbed
             self.assertTrue(debug_mock.called)
 
-    def test_cpu_features_bug_1217630(self):
-        conn = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
-
-        # Test old version of libvirt, it shouldn't see the `aes' feature
-        with mock.patch('nova.virt.libvirt.driver.libvirt') as mock_libvirt:
-            del mock_libvirt.VIR_CONNECT_BASELINE_CPU_EXPAND_FEATURES
-            caps = conn._get_host_capabilities()
-            self.assertNotIn('aes', [x.name for x in caps.host.cpu.features])
-
-        # Test new verion of libvirt, should find the `aes' feature
-        with mock.patch('nova.virt.libvirt.driver.libvirt') as mock_libvirt:
-            mock_libvirt['VIR_CONNECT_BASELINE_CPU_EXPAND_FEATURES'] = 1
-            # Cleanup the capabilities cache firstly
-            conn._caps = None
-            caps = conn._get_host_capabilities()
-            self.assertIn('aes', [x.name for x in caps.host.cpu.features])
-
-    def test_cpu_features_are_not_duplicated(self):
-        conn = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
-
-        # Test old version of libvirt. Should return single 'hypervisor'
-        with mock.patch('nova.virt.libvirt.driver.libvirt') as mock_libvirt:
-            del mock_libvirt.VIR_CONNECT_BASELINE_CPU_EXPAND_FEATURES
-            caps = conn._get_host_capabilities()
-            cnt = [x.name for x in caps.host.cpu.features].count('hypervisor')
-            self.assertEqual(1, cnt)
-
-        # Test new version of libvirt. Should still return single 'hypervisor'
-        with mock.patch('nova.virt.libvirt.driver.libvirt') as mock_libvirt:
-            mock_libvirt['VIR_CONNECT_BASELINE_CPU_EXPAND_FEATURES'] = 1
-            # Cleanup the capabilities cache firstly
-            conn._caps = None
-            caps = conn._get_host_capabilities()
-            cnt = [x.name for x in caps.host.cpu.features].count('hypervisor')
-            self.assertEqual(1, cnt)
-
-    def test_baseline_cpu_not_supported(self):
-        conn = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
-
-        # `mock` has trouble stubbing attributes that don't exist yet, so
-        # fallback to plain-Python attribute setting/deleting
-        cap_str = 'VIR_CONNECT_BASELINE_CPU_EXPAND_FEATURES'
-        if not hasattr(libvirt_driver.libvirt, cap_str):
-            setattr(libvirt_driver.libvirt, cap_str, True)
-            self.addCleanup(delattr, libvirt_driver.libvirt, cap_str)
-
-        # Handle just the NO_SUPPORT error
-        not_supported_exc = fakelibvirt.make_libvirtError(
-                libvirt.libvirtError,
-                'this function is not supported by the connection driver:'
-                ' virConnectBaselineCPU',
-                error_code=libvirt.VIR_ERR_NO_SUPPORT)
-
-        with mock.patch.object(conn._conn, 'baselineCPU',
-                               side_effect=not_supported_exc):
-            caps = conn._get_host_capabilities()
-            self.assertEqual(vconfig.LibvirtConfigCaps, type(caps))
-            self.assertNotIn('aes', [x.name for x in caps.host.cpu.features])
-
-        # Clear cached result so we can test again...
-        conn._caps = None
-
-        # Other errors should not be caught
-        other_exc = fakelibvirt.make_libvirtError(
-            libvirt.libvirtError,
-            'other exc',
-            error_code=libvirt.VIR_ERR_NO_DOMAIN)
-
-        with mock.patch.object(conn._conn, 'baselineCPU',
-                               side_effect=other_exc):
-            self.assertRaises(libvirt.libvirtError,
-                              conn._get_host_capabilities)
-
-    def test_lxc_get_host_capabilities_failed(self):
-        conn = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
-
-        with mock.patch.object(conn._conn, 'baselineCPU', return_value=-1):
-            setattr(libvirt, 'VIR_CONNECT_BASELINE_CPU_EXPAND_FEATURES', 1)
-            caps = conn._get_host_capabilities()
-            delattr(libvirt, 'VIR_CONNECT_BASELINE_CPU_EXPAND_FEATURES')
-            self.assertEqual(vconfig.LibvirtConfigCaps, type(caps))
-            self.assertNotIn('aes', [x.name for x in caps.host.cpu.features])
-
     @mock.patch.object(time, "time")
     def test_get_guest_config(self, time_mock):
         time_mock.return_value = 1234567.89
@@ -1220,8 +1136,8 @@ class LibvirtConnTestCase(test.NoDBTestCase):
         with contextlib.nested(
                 mock.patch.object(host.Host, 'has_min_version',
                                   return_value=True),
-                mock.patch.object(
-                    conn, "_get_host_capabilities", return_value=caps),
+                mock.patch.object(host.Host, "get_capabilities",
+                                  return_value=caps),
                 mock.patch.object(
                         random, 'choice', side_effect=lambda cells: cells[0])):
             cfg = conn._get_guest_config(instance_ref, [], {}, disk_info)
@@ -1248,8 +1164,8 @@ class LibvirtConnTestCase(test.NoDBTestCase):
                                             instance_ref)
 
         with contextlib.nested(
-                mock.patch.object(
-                    conn, "_get_host_capabilities", return_value=caps),
+                mock.patch.object(host.Host, "get_capabilities",
+                                  return_value=caps),
                 mock.patch.object(
                     hardware, 'get_vcpu_pin_set', return_value=set([3])),
                 mock.patch.object(random, 'choice')
@@ -1319,8 +1235,8 @@ class LibvirtConnTestCase(test.NoDBTestCase):
         with contextlib.nested(
                 mock.patch.object(host.Host, 'has_min_version',
                                   return_value=True),
-                mock.patch.object(
-                    conn, "_get_host_capabilities", return_value=caps),
+                mock.patch.object(host.Host, "get_capabilities",
+                                  return_value=caps),
                 mock.patch.object(
                     hardware, 'get_vcpu_pin_set', return_value=set([2, 3])),
                 mock.patch.object(
@@ -1365,8 +1281,8 @@ class LibvirtConnTestCase(test.NoDBTestCase):
                     return_value=instance_topology),
                 mock.patch.object(host.Host, 'has_min_version',
                                   return_value=True),
-                mock.patch.object(
-                    conn, "_get_host_capabilities", return_value=caps)):
+                mock.patch.object(host.Host, "get_capabilities",
+                                  return_value=caps)):
             cfg = conn._get_guest_config(instance_ref, [], {}, disk_info)
             self.assertIsNone(cfg.cpuset)
             self.assertEqual(0, len(cfg.cputune.vcpupin))
@@ -1412,8 +1328,8 @@ class LibvirtConnTestCase(test.NoDBTestCase):
                     return_value=instance_topology),
                 mock.patch.object(host.Host, 'has_min_version',
                                   return_value=True),
-                mock.patch.object(
-                    conn, "_get_host_capabilities", return_value=caps),
+                mock.patch.object(host.Host, "get_capabilities",
+                                  return_value=caps),
                 mock.patch.object(
                     hardware, 'get_vcpu_pin_set',
                     return_value=set([2, 3, 4, 5]))
@@ -1489,8 +1405,8 @@ class LibvirtConnTestCase(test.NoDBTestCase):
                     return_value=instance_topology),
                 mock.patch.object(host.Host, 'has_min_version',
                                   return_value=True),
-                mock.patch.object(
-                    conn, "_get_host_capabilities", return_value=caps),
+                mock.patch.object(host.Host, "get_capabilities",
+                                  return_value=caps),
                 ):
             cfg = conn._get_guest_config(instance_ref, [], {}, disk_info)
             self.assertIsNone(cfg.cpuset)
@@ -2483,8 +2399,7 @@ class LibvirtConnTestCase(test.NoDBTestCase):
             caps.host.cpu = cpu
             return caps
 
-        self.stubs.Set(libvirt_driver.LibvirtDriver,
-                       "_get_host_capabilities",
+        self.stubs.Set(host.Host, "get_capabilities",
                        get_host_capabilities_stub)
 
     def _stub_guest_cpu_config_arch(self, cpu_arch):
@@ -3621,8 +3536,7 @@ class LibvirtConnTestCase(test.NoDBTestCase):
         disk_info = blockinfo.get_disk_info(CONF.libvirt.virt_type,
                                             instance_ref)
 
-        self.stubs.Set(libvirt_driver.LibvirtDriver,
-                       "_get_host_capabilities",
+        self.stubs.Set(host.Host, "get_capabilities",
                        get_host_capabilities_stub)
 
         conn = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
@@ -3653,8 +3567,7 @@ class LibvirtConnTestCase(test.NoDBTestCase):
         disk_info = blockinfo.get_disk_info(CONF.libvirt.virt_type,
                                             instance_ref)
 
-        self.stubs.Set(libvirt_driver.LibvirtDriver,
-                       "_get_host_capabilities",
+        self.stubs.Set(host.Host, "get_capabilities",
                        get_host_capabilities_stub)
 
         conn = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
@@ -8651,8 +8564,7 @@ class LibvirtConnTestCase(test.NoDBTestCase):
 
             return caps
 
-        self.stubs.Set(libvirt_driver.LibvirtDriver,
-                       '_get_host_capabilities',
+        self.stubs.Set(host.Host, "get_capabilities",
                        get_host_capabilities_stub)
 
         want = {"vendor": "AMD",
@@ -8845,8 +8757,8 @@ class LibvirtConnTestCase(test.NoDBTestCase):
         with contextlib.nested(
                 mock.patch.object(host.Host, 'has_min_version',
                                   return_value=True),
-                mock.patch.object(
-                    conn, '_get_host_capabilities', return_value=caps),
+                mock.patch.object(host.Host, "get_capabilities",
+                                  return_value=caps),
                 mock.patch.object(
                     hardware, 'get_vcpu_pin_set', return_value=set([0, 1, 3]))
                 ):
@@ -8873,7 +8785,7 @@ class LibvirtConnTestCase(test.NoDBTestCase):
         conn = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), False)
         with contextlib.nested(
             mock.patch.object(host.Host, 'has_min_version', return_value=True),
-            mock.patch.object(conn, '_get_host_capabilities',
+            mock.patch.object(host.Host, "get_capabilities",
                               return_value=caps)
         ) as (has_min_version, get_caps):
             self.assertIsNone(conn._get_host_numa_topology())
@@ -9606,8 +9518,7 @@ Active:          8381604 kB
 
             return caps
 
-        self.stubs.Set(libvirt_driver.LibvirtDriver,
-                       '_get_host_capabilities',
+        self.stubs.Set(host.Host, "get_capabilities",
                        get_host_capabilities_stub)
 
         want = [(arch.X86_64, 'kvm', 'hvm'),
@@ -10235,21 +10146,15 @@ Active:          8381604 kB
         network_info = _fake_network_info(self.stubs, 1)
         self.create_fake_libvirt_mock(getLibVersion=fake_getLibVersion,
                                       getCapabilities=fake_getCapabilities,
-                                      getVersion=lambda: 1005001)
+                                      getVersion=lambda: 1005001,
+                                      listDefinedDomains=lambda: [],
+                                      baselineCPU=fake_baselineCPU)
         instance_ref = self.test_instance
         instance_ref['image_ref'] = 123456  # we send an int to test sha1 call
         instance = objects.Instance(**instance_ref)
         flavor = instance.get_flavor()
         flavor.extra_specs = {}
 
-        self.mox.StubOutWithMock(libvirt_driver.LibvirtDriver, '_conn')
-        libvirt_driver.LibvirtDriver._conn.listDefinedDomains = lambda: []
-        libvirt_driver.LibvirtDriver._conn.getCapabilities = \
-                                                        fake_getCapabilities
-        libvirt_driver.LibvirtDriver._conn.getVersion = lambda: 1005001
-        libvirt_driver.LibvirtDriver._conn.defineXML = fake_defineXML
-        libvirt_driver.LibvirtDriver._conn.baselineCPU = fake_baselineCPU
-
         self.mox.ReplayAll()
 
         conn = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), False)
diff --git a/nova/tests/unit/virt/libvirt/test_host.py b/nova/tests/unit/virt/libvirt/test_host.py
index 04b2bccfa0..21d72d8397 100644
--- a/nova/tests/unit/virt/libvirt/test_host.py
+++ b/nova/tests/unit/virt/libvirt/test_host.py
@@ -25,6 +25,7 @@ from nova import objects
 from nova import test
 from nova.tests.unit.virt.libvirt import fakelibvirt
 from nova.virt import event
+from nova.virt.libvirt import config as vconfig
 from nova.virt.libvirt import host
 
 try:
@@ -551,3 +552,85 @@ class HostTestCase(test.NoDBTestCase):
         self.assertEqual(doms[1].name(), vm1.name())
         self.assertEqual(doms[2].name(), vm2.name())
         mock_list.assert_called_with(True)
+
+    def test_cpu_features_bug_1217630(self):
+        self.host.get_connection()
+
+        # Test old version of libvirt, it shouldn't see the `aes' feature
+        with mock.patch('nova.virt.libvirt.host.libvirt') as mock_libvirt:
+            del mock_libvirt.VIR_CONNECT_BASELINE_CPU_EXPAND_FEATURES
+            caps = self.host.get_capabilities()
+            self.assertNotIn('aes', [x.name for x in caps.host.cpu.features])
+
+        # Cleanup the capabilities cache firstly
+        self.host._caps = None
+
+        # Test new version of libvirt, should find the `aes' feature
+        with mock.patch('nova.virt.libvirt.host.libvirt') as mock_libvirt:
+            mock_libvirt['VIR_CONNECT_BASELINE_CPU_EXPAND_FEATURES'] = 1
+            caps = self.host.get_capabilities()
+            self.assertIn('aes', [x.name for x in caps.host.cpu.features])
+
+    def test_cpu_features_are_not_duplicated(self):
+        self.host.get_connection()
+
+        # Test old version of libvirt. Should return single 'hypervisor'
+        with mock.patch('nova.virt.libvirt.host.libvirt') as mock_libvirt:
+            del mock_libvirt.VIR_CONNECT_BASELINE_CPU_EXPAND_FEATURES
+            caps = self.host.get_capabilities()
+            cnt = [x.name for x in caps.host.cpu.features].count('xtpr')
+            self.assertEqual(1, cnt)
+
+        # Cleanup the capabilities cache firstly
+        self.host._caps = None
+
+        # Test new version of libvirt. Should still return single 'hypervisor'
+        with mock.patch('nova.virt.libvirt.host.libvirt') as mock_libvirt:
+            mock_libvirt['VIR_CONNECT_BASELINE_CPU_EXPAND_FEATURES'] = 1
+            caps = self.host.get_capabilities()
+            cnt = [x.name for x in caps.host.cpu.features].count('xtpr')
+            self.assertEqual(1, cnt)
+
+    def test_baseline_cpu_not_supported(self):
+        # `mock` has trouble stubbing attributes that don't exist yet, so
+        # fallback to plain-Python attribute setting/deleting
+        cap_str = 'VIR_CONNECT_BASELINE_CPU_EXPAND_FEATURES'
+        if not hasattr(host.libvirt, cap_str):
+            setattr(host.libvirt, cap_str, True)
+            self.addCleanup(delattr, host.libvirt, cap_str)
+
+        # Handle just the NO_SUPPORT error
+        not_supported_exc = fakelibvirt.make_libvirtError(
+                libvirt.libvirtError,
+                'this function is not supported by the connection driver:'
+                ' virConnectBaselineCPU',
+                error_code=libvirt.VIR_ERR_NO_SUPPORT)
+
+        with mock.patch.object(fakelibvirt.virConnect, 'baselineCPU',
+                               side_effect=not_supported_exc):
+            caps = self.host.get_capabilities()
+            self.assertEqual(vconfig.LibvirtConfigCaps, type(caps))
+            self.assertNotIn('aes', [x.name for x in caps.host.cpu.features])
+
+        # Clear cached result so we can test again...
+        self.host._caps = None
+
+        # Other errors should not be caught
+        other_exc = fakelibvirt.make_libvirtError(
+            libvirt.libvirtError,
+            'other exc',
+            error_code=libvirt.VIR_ERR_NO_DOMAIN)
+
+        with mock.patch.object(fakelibvirt.virConnect, 'baselineCPU',
+                               side_effect=other_exc):
+            self.assertRaises(libvirt.libvirtError,
+                              self.host.get_capabilities)
+
+    def test_lxc_get_host_capabilities_failed(self):
+        with mock.patch.object(fakelibvirt.virConnect, 'baselineCPU',
+                               return_value=-1):
+            setattr(libvirt, 'VIR_CONNECT_BASELINE_CPU_EXPAND_FEATURES', 1)
+            caps = self.host.get_capabilities()
+            delattr(libvirt, 'VIR_CONNECT_BASELINE_CPU_EXPAND_FEATURES')
+            self.assertEqual(vconfig.LibvirtConfigCaps, type(caps))
+            self.assertNotIn('aes', [x.name for x in caps.host.cpu.features])
diff --git a/nova/virt/libvirt/driver.py b/nova/virt/libvirt/driver.py
index f4223a3128..9d4bb95f09 100644
--- a/nova/virt/libvirt/driver.py
+++ b/nova/virt/libvirt/driver.py
@@ -495,7 +495,7 @@ class LibvirtDriver(driver.ComputeDriver):
         unknown. Currently, only qemu or kvm on intel 32- or 64-bit systems
         is tested upstream.
         """
-        caps = self._get_host_capabilities()
+        caps = self._host.get_capabilities()
         hostarch = caps.host.cpu.arch
         if (CONF.libvirt.virt_type not in ('qemu', 'kvm') or
             hostarch not in (arch.I686, arch.X86_64)):
@@ -2991,37 +2991,6 @@ class LibvirtDriver(driver.ComputeDriver):
                          'due to an unexpected exception.'), CONF.host,
                      exc_info=True)
 
-    def _get_host_capabilities(self):
-        """Returns an instance of config.LibvirtConfigCaps representing
-           the capabilities of the host.
-        """
-        if not self._caps:
-            xmlstr = self._conn.getCapabilities()
-            self._caps = vconfig.LibvirtConfigCaps()
-            self._caps.parse_str(xmlstr)
-            if hasattr(libvirt, 'VIR_CONNECT_BASELINE_CPU_EXPAND_FEATURES'):
-                try:
-                    features = self._conn.baselineCPU(
-                        [self._caps.host.cpu.to_xml()],
-                        libvirt.VIR_CONNECT_BASELINE_CPU_EXPAND_FEATURES)
-                    # FIXME(wangpan): the return value of baselineCPU should be
-                    #                 None or xml string, but libvirt has a bug
-                    #                 of it from 1.1.2 which is fixed in 1.2.0,
-                    #                 this -1 checking should be removed later.
-                    if features and features != -1:
-                        cpu = vconfig.LibvirtConfigCPU()
-                        cpu.parse_str(features)
-                        self._caps.host.cpu.features = cpu.features
-                except libvirt.libvirtError as ex:
-                    error_code = ex.get_error_code()
-                    if error_code == libvirt.VIR_ERR_NO_SUPPORT:
-                        LOG.warn(_LW("URI %(uri)s does not support full set"
-                                     " of host capabilities: " "%(error)s"),
-                                     {'uri': self.uri(), 'error': ex})
-                    else:
-                        raise
-        return self._caps
-
     def _get_guest_cpu_model_config(self):
         mode = CONF.libvirt.cpu_mode
         model = CONF.libvirt.cpu_model
@@ -3204,7 +3173,7 @@ class LibvirtDriver(driver.ComputeDriver):
         This is typically from the SMBIOS data, unless it has
         been overridden in /etc/libvirt/libvirtd.conf
         """
-        caps = self._get_host_capabilities()
+        caps = self._host.get_capabilities()
         return caps.host.uuid
 
     def _get_host_sysinfo_serial_os(self):
@@ -3820,7 +3789,7 @@ class LibvirtDriver(driver.ComputeDriver):
 
         if guest.os_type is None:
             guest.os_type = self._get_guest_os_type(virt_type)
-        caps = self._get_host_capabilities()
+        caps = self._host.get_capabilities()
 
         if virt_type == "xen":
             if guest.os_type == vm_mode.HVM:
@@ -4476,7 +4445,7 @@ class LibvirtDriver(driver.ComputeDriver):
 
         :returns: List of tuples describing instance capabilities
         """
-        caps = self._get_host_capabilities()
+        caps = self._host.get_capabilities()
         instance_caps = list()
         for g in caps.guests:
             for dt in g.domtype:
@@ -4498,7 +4467,7 @@ class LibvirtDriver(driver.ComputeDriver):
 
         """
 
-        caps = self._get_host_capabilities()
+        caps = self._host.get_capabilities()
         cpu_info = dict()
 
         cpu_info['arch'] = caps.host.cpu.arch
@@ -4624,7 +4593,7 @@ class LibvirtDriver(driver.ComputeDriver):
         if not self._host.has_min_version(MIN_LIBVIRT_NUMA_TOPOLOGY_VERSION):
             return
 
-        caps = self._get_host_capabilities()
+        caps = self._host.get_capabilities()
         topology = caps.host.topology
 
         if topology is None or not topology.cells:
diff --git a/nova/virt/libvirt/host.py b/nova/virt/libvirt/host.py
index 037197c131..9f8e45bea7 100644
--- a/nova/virt/libvirt/host.py
+++ b/nova/virt/libvirt/host.py
@@ -48,6 +48,7 @@ from nova.openstack.common import log as logging
 from nova import rpc
 from nova import utils
 from nova.virt import event as virtevent
+from nova.virt.libvirt import config as vconfig
 
 libvirt = None
 
@@ -77,6 +78,7 @@ class Host(object):
         self._conn_event_handler = conn_event_handler
         self._lifecycle_event_handler = lifecycle_event_handler
         self._skip_list_all_domains = False
+        self._caps = None
 
         self._wrapped_conn = None
         self._wrapped_conn_lock = threading.Lock()
@@ -573,3 +575,34 @@ class Host(object):
             doms.append(dom)
 
         return doms
+
+    def get_capabilities(self):
+        """Returns an instance of config.LibvirtConfigCaps representing
+           the capabilities of the host.
+        """
+        if not self._caps:
+            xmlstr = self.get_connection().getCapabilities()
+            self._caps = vconfig.LibvirtConfigCaps()
+            self._caps.parse_str(xmlstr)
+            if hasattr(libvirt, 'VIR_CONNECT_BASELINE_CPU_EXPAND_FEATURES'):
+                try:
+                    features = self.get_connection().baselineCPU(
+                        [self._caps.host.cpu.to_xml()],
+                        libvirt.VIR_CONNECT_BASELINE_CPU_EXPAND_FEATURES)
+                    # FIXME(wangpan): the return value of baselineCPU should be
+                    #                 None or xml string, but libvirt has a bug
+                    #                 of it from 1.1.2 which is fixed in 1.2.0,
+                    #                 this -1 checking should be removed later.
+                    if features and features != -1:
+                        cpu = vconfig.LibvirtConfigCPU()
+                        cpu.parse_str(features)
+                        self._caps.host.cpu.features = cpu.features
+                except libvirt.libvirtError as ex:
+                    error_code = ex.get_error_code()
+                    if error_code == libvirt.VIR_ERR_NO_SUPPORT:
+                        LOG.warn(_LW("URI %(uri)s does not support full set"
+                                     " of host capabilities: " "%(error)s"),
+                                     {'uri': self._uri, 'error': ex})
+                    else:
+                        raise
+        return self._caps