Merge "libvirt: At start-up rework compareCPU() usage with a workaround" into stable/zed

nova/conf/workarounds.py

@@ -410,6 +410,13 @@ with the destination host. When using QEMU >= 2.9 and libvirt >=
 4.4.0, libvirt will do the correct thing with respect to checking CPU
 compatibility on the destination host during live migration.
 """),
+    cfg.BoolOpt('skip_cpu_compare_at_startup',
+               default=False,
+               help="""
+This will skip the CPU comparison call at the startup of Compute
+service and lets libvirt handle it.
+"""),
+
     cfg.BoolOpt(
         'skip_hypervisor_version_check_on_lm',
         default=False,

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

@@ -1331,6 +1331,22 @@ class LibvirtConnTestCase(test.NoDBTestCase,
         self.assertRaises(exception.InvalidCPUInfo,
                           drvr.init_host, "dummyhost")
 
+    @mock.patch.object(libvirt_driver.LibvirtDriver,
+                       '_register_all_undefined_instance_details',
+                       new=mock.Mock())
+    @mock.patch('nova.virt.libvirt.host.libvirt.Connection.compareCPU')
+    def test__check_cpu_compatibility_skip_compare_at_init(
+            self, mocked_compare
+    ):
+        self.flags(group='workarounds', skip_cpu_compare_at_startup=True)
+        self.flags(cpu_mode="custom",
+                   cpu_models=["Icelake-Server-noTSX"],
+                   cpu_model_extra_flags = ["-mpx"],
+                   group="libvirt")
+        drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
+        drvr.init_host("dummyhost")
+        mocked_compare.assert_not_called()
+
     @mock.patch.object(libvirt_driver.LibvirtDriver,
                        '_register_all_undefined_instance_details',
                        new=mock.Mock())
@@ -1344,7 +1360,7 @@ class LibvirtConnTestCase(test.NoDBTestCase,
 
     @mock.patch('nova.virt.libvirt.host.libvirt.Connection.compareCPU')
     def test__check_cpu_compatibility_advance_flag(self, mocked_compare):
-        mocked_compare.side_effect = (2, 0)
+        mocked_compare.side_effect = (-1, 0)
         self.flags(cpu_mode="custom",
                    cpu_models=["qemu64"],
                    cpu_model_extra_flags = ["avx", "avx2"],
@@ -1357,7 +1373,7 @@ class LibvirtConnTestCase(test.NoDBTestCase,
     def test__check_cpu_compatibility_wrong_flag(self, mocked_compare):
         # here, and in the surrounding similar tests, the non-zero error
         # code in the compareCPU() side effect indicates error
-        mocked_compare.side_effect = (2, 0)
+        mocked_compare.side_effect = (-1, 0)
         self.flags(cpu_mode="custom",
                    cpu_models=["Broadwell-noTSX"],
                    cpu_model_extra_flags = ["a v x"],
@@ -1370,7 +1386,7 @@ class LibvirtConnTestCase(test.NoDBTestCase,
     def test__check_cpu_compatibility_enabled_and_disabled_flags(
             self, mocked_compare
     ):
-        mocked_compare.side_effect = (2, 0)
+        mocked_compare.side_effect = (-1, 0)
         self.flags(
             cpu_mode="custom",
             cpu_models=["Cascadelake-Server"],

nova/virt/libvirt/driver.py

@@ -984,33 +984,26 @@ class LibvirtDriver(driver.ComputeDriver):
             msg = _("The cpu_models option is required when cpu_mode=custom")
             raise exception.Invalid(msg)
 
-        cpu = vconfig.LibvirtConfigGuestCPU()
-        for model in models:
-            cpu.model = self._get_cpu_model_mapping(model)
-            try:
-                self._compare_cpu(cpu, self._get_cpu_info(), None)
-            except exception.InvalidCPUInfo as e:
-                msg = (_("Configured CPU model: %(model)s is not "
-                         "compatible with host CPU. Please correct your "
-                         "config and try again. %(e)s") % {
-                            'model': model, 'e': e})
-                raise exception.InvalidCPUInfo(msg)
-
-        # Use guest CPU model to check the compatibility between guest CPU and
-        # configured extra_flags
-        cpu = vconfig.LibvirtConfigGuestCPU()
-        cpu.model = self._host.get_capabilities().host.cpu.model
-        for flag in set(x.lower() for x in CONF.libvirt.cpu_model_extra_flags):
-            cpu_feature = self._prepare_cpu_flag(flag)
-            cpu.add_feature(cpu_feature)
-            try:
-                self._compare_cpu(cpu, self._get_cpu_info(), None)
-            except exception.InvalidCPUInfo as e:
-                msg = (_("Configured extra flag: %(flag)s it not correct, or "
-                         "the host CPU does not support this flag. Please "
-                         "correct the config and try again. %(e)s") % {
-                            'flag': flag, 'e': e})
-                raise exception.InvalidCPUInfo(msg)
+        if not CONF.workarounds.skip_cpu_compare_at_startup:
+            # Use guest CPU model to check the compatibility between
+            # guest CPU and configured extra_flags
+            for model in models:
+                cpu = vconfig.LibvirtConfigGuestCPU()
+                cpu.model = self._get_cpu_model_mapping(model)
+                for flag in set(x.lower() for
+                                x in CONF.libvirt.cpu_model_extra_flags):
+                    cpu_feature = self._prepare_cpu_flag(flag)
+                    cpu.add_feature(cpu_feature)
+                try:
+                    self._compare_cpu(cpu, self._get_cpu_info(), None)
+                except exception.InvalidCPUInfo as e:
+                    msg = (_("Configured CPU model: %(model)s "
+                             "and CPU Flags %(flags)s ar not "
+                             "compatible with host CPU. Please correct your "
+                             "config and try again. %(e)s") % {
+                                'model': model, 'e': e,
+                                'flags': CONF.libvirt.cpu_model_extra_flags})
+                    raise exception.InvalidCPUInfo(msg)
 
     def _check_vtpm_support(self) -> None:
         # TODO(efried): A key manager must be configured to create/retrieve