Merge "Remove support for Intel CMT events"

Author: Zuul

nova/conf/libvirt.py

@@ -783,15 +783,13 @@
     cfg.ListOpt('enabled_perf_events',
                default=[],
                help= """
+Performance events to monitor and collect statistics for.
+
 This will allow you to specify a list of events to monitor low-level
-performance of guests, and collect related statsitics via the libvirt
-driver, which in turn uses the Linux kernel's `perf` infrastructure.
+performance of guests, and collect related statistics via the libvirt
+driver, which in turn uses the Linux kernel's ``perf`` infrastructure.
 With this config attribute set, Nova will generate libvirt guest XML to
-monitor the specified events.  For more information, refer to the
-"Performance monitoring events" section here:
-https://libvirt.org/formatdomain.html#elementsPerf.  And here:
-https://libvirt.org/html/libvirt-libvirt-domain.html -- look for
-``VIR_PERF_PARAM_*``
+monitor the specified events.
 
 For example, to monitor the count of CPU cycles (total/elapsed) and the
 count of cache misses, enable them as follows::
@@ -800,12 +798,11 @@
     enabled_perf_events = cpu_clock, cache_misses
 
 Possible values: A string list.  The list of supported events can be
-found here: https://libvirt.org/formatdomain.html#elementsPerf.
+found `here`__. Note that Intel CMT events - ``cmt``, ``mbmbt`` and
+``mbml`` - are unsupported by recent Linux kernel versions (4.14+) and will be
+ignored by nova.
 
-Note that support for Intel CMT events (`cmt`, `mbmbt`, `mbml`) is
-deprecated, and will be removed in the "Stein" release.  That's because
-the upstream Linux kernel (from 4.14 onwards) has deleted support for
-Intel CMT, because it is broken by design.
+__ https://libvirt.org/formatdomain.html#elementsPerf.
 """),
     cfg.IntOpt('num_pcie_ports',
                default=0,

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

@@ -8613,97 +8613,19 @@ def test_get_guest_memory_balloon_config_lxc(self):
                 break
         self.assertTrue(no_exist)
 
-    @mock.patch('nova.virt.libvirt.driver.LOG.warning')
-    @mock.patch.object(host.Host, 'has_min_version', return_value=True)
-    @mock.patch.object(host.Host, "get_capabilities")
-    def test_get_supported_perf_events_foo(self, mock_get_caps,
-                                           mock_min_version,
-                                           mock_warn):
-        self.flags(enabled_perf_events=['foo'], group='libvirt')
-
-        caps = vconfig.LibvirtConfigCaps()
-        caps.host = vconfig.LibvirtConfigCapsHost()
-        caps.host.cpu = vconfig.LibvirtConfigCPU()
-        caps.host.cpu.arch = fields.Architecture.X86_64
-        caps.host.topology = fakelibvirt.NUMATopology()
+    @mock.patch.object(libvirt_driver, 'LOG')
+    @mock.patch.object(
+        fakelibvirt, 'VIR_PERF_PARAM_CPU_CLOCK', 'cpu_clock', create=True)
+    @mock.patch.object(fakelibvirt, 'VIR_PERF_PARAM_CMT', 'cmt', create=True)
+    def test_get_supported_perf_events(self, mock_log):
+        self.flags(
+            enabled_perf_events=['cpu_clock', 'foo', 'cmt'], group='libvirt')
 
-        mock_get_caps.return_value = caps
         drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
         events = drvr._get_supported_perf_events()
 
-        self.assertTrue(mock_warn.called)
-        self.assertEqual([], events)
-
-    @mock.patch.object(host.Host, "get_capabilities")
-    def _test_get_guest_with_perf(self, caps, events, mock_get_caps):
-        mock_get_caps.return_value = caps
-
-        drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
-        drvr.init_host('test_perf')
-        instance_ref = objects.Instance(**self.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)
-
-        self.assertEqual(events, cfg.perf_events)
-
-    @mock.patch.object(fakelibvirt, 'VIR_PERF_PARAM_CMT', True,
-                       create=True)
-    @mock.patch.object(host.Host, 'has_min_version', return_value=True)
-    def test_get_guest_with_perf_host_unsupported(self,
-                                             mock_min_version):
-        self.flags(enabled_perf_events=['cmt'], group='libvirt')
-        caps = vconfig.LibvirtConfigCaps()
-        caps.host = vconfig.LibvirtConfigCapsHost()
-        caps.host.cpu = vconfig.LibvirtConfigCPU()
-        caps.host.cpu.arch = fields.Architecture.X86_64
-        caps.host.topology = fakelibvirt.NUMATopology()
-
-        self._test_get_guest_with_perf(caps, [])
-
-    @mock.patch.object(fakelibvirt, 'VIR_PERF_PARAM_CMT', True,
-                       create=True)
-    @mock.patch.object(fakelibvirt, 'VIR_PERF_PARAM_MBMT', True,
-                       create=True)
-    @mock.patch.object(fakelibvirt, 'VIR_PERF_PARAM_MBML', True,
-                       create=True)
-    @mock.patch.object(libvirt_driver.LOG, 'warning')
-    @mock.patch.object(host.Host, 'has_min_version', return_value=True)
-    def test_intel_cmt_perf_deprecation_warning(self,
-                                             mock_min_version,
-                                             mock_warn):
-        perf_events = ['cmt', 'mbml', 'mbmt']
-        self.flags(enabled_perf_events=['cmt', 'mbml', 'mbmt'],
-                   group='libvirt')
-        caps = vconfig.LibvirtConfigCaps()
-        caps.host = vconfig.LibvirtConfigCapsHost()
-        caps.host.cpu = vconfig.LibvirtConfigCPU()
-        caps.host.cpu.arch = fields.Architecture.X86_64
-        caps.host.topology = fakelibvirt.NUMATopology()
-
-        features = []
-        for f in ('cmt', 'mbm_local', 'mbm_total'):
-            feature = vconfig.LibvirtConfigGuestCPUFeature()
-            feature.name = f
-            feature.policy = fields.CPUFeaturePolicy.REQUIRE
-            features.append(feature)
-
-        caps.host.cpu.features = set(features)
-        self._test_get_guest_with_perf(caps, ['cmt', 'mbml', 'mbmt'])
-        warning_count = 0
-        call_args_list = mock_warn.call_args_list
-        for call in call_args_list:
-            # Call can be unpackaged as a tuple of args and kwargs
-            # so we want to check the first arg in the args list
-            if (len(call) == 2 and len(call[0]) == 2 and
-                    call[0][1] in perf_events and
-                    'Monitoring Intel CMT' in call[0][0]):
-                warning_count += 1
-        self.assertEqual(3, warning_count)
+        self.assertEqual(['cpu_clock'], events)
+        self.assertEqual(2, len(mock_log.warning.mock_calls))
 
     def test_xml_and_uri_no_ramdisk_no_kernel(self):
         instance_data = dict(self.test_instance)

nova/virt/libvirt/driver.py

@@ -248,11 +248,6 @@ def repr_method(self):
 
 LIBVIRT_PERF_EVENT_PREFIX = 'VIR_PERF_PARAM_'
 
-PERF_EVENTS_CPU_FLAG_MAPPING = {'cmt': 'cmt',
-                                'mbml': 'mbm_local',
-                                'mbmt': 'mbm_total',
-                               }
-
 MIN_LIBVIRT_FILE_BACKED_DISCARD_VERSION = (4, 4, 0)
 
 MIN_LIBVIRT_NATIVE_TLS_VERSION = (4, 4, 0)
@@ -5686,37 +5681,28 @@ def _check_uefi_support(self, hw_firmware_type):
                  caps.host.cpu.arch == fields.Architecture.AARCH64))
 
     def _get_supported_perf_events(self):
-
-        if (len(CONF.libvirt.enabled_perf_events) == 0):
+        if not len(CONF.libvirt.enabled_perf_events):
             return []
 
         supported_events = []
-        host_cpu_info = self._get_cpu_info()
         for event in CONF.libvirt.enabled_perf_events:
-            if self._supported_perf_event(event, host_cpu_info['features']):
-                supported_events.append(event)
-        return supported_events
+            libvirt_perf_event_name = LIBVIRT_PERF_EVENT_PREFIX + event.upper()
 
-    def _supported_perf_event(self, event, cpu_features):
+            if not hasattr(libvirt, libvirt_perf_event_name):
+                LOG.warning("Libvirt does not support event type '%s'.", event)
+                continue
 
-        libvirt_perf_event_name = LIBVIRT_PERF_EVENT_PREFIX + event.upper()
+            if event in ('cmt', 'mbml', 'mbmt'):
+                LOG.warning(
+                    "Monitoring of Intel CMT `perf` event(s) '%s' is not "
+                    "supported by recent Linux kernels; ignoring.",
+                    event,
+                )
+                continue
 
-        if not hasattr(libvirt, libvirt_perf_event_name):
-            LOG.warning("Libvirt doesn't support event type %s.", event)
-            return False
+            supported_events.append(event)
 
-        if event in PERF_EVENTS_CPU_FLAG_MAPPING:
-            LOG.warning('Monitoring Intel CMT `perf` event(s) %s is '
-                        'deprecated and will be removed in the "Stein" '
-                        'release.  It was broken by design in the '
-                        'Linux kernel, so support for Intel CMT was '
-                        'removed from Linux 4.14 onwards. Therefore '
-                        'it is recommended to not enable them.',
-                        event)
-            if PERF_EVENTS_CPU_FLAG_MAPPING[event] not in cpu_features:
-                LOG.warning("Host does not support event type %s.", event)
-                return False
-        return True
+        return supported_events
 
     def _configure_guest_by_virt_type(self, guest, virt_type, caps, instance,
                                       image_meta, flavor, root_device_name,

releasenotes/notes/remove-intel-cmt-perf-events-69df7324d6fe41a8.yaml

@@ -0,0 +1,7 @@
+---
+upgrade:
+  - |
+    Intel CMT perf events - ``cmt``, ``mbmt``, and ``mbml`` - are no longer
+    supported by the ``[libvirt] enabled_perf_events`` config option. These
+    event types were broken by design and are not supported in recent Linux
+    kernels (4.14+).