diff options
| -rw-r--r-- | nova/conf/workarounds.py | 8 | ||||
| -rw-r--r-- | nova/tests/unit/virt/libvirt/test_driver.py | 19 | ||||
| -rw-r--r-- | nova/virt/libvirt/driver.py | 19 | ||||
| -rw-r--r-- | releasenotes/notes/skip-compare-cpu-on-dest-6ae419ddd61fd0f8.yaml | 24 |
4 files changed, 61 insertions, 9 deletions
diff --git a/nova/conf/workarounds.py b/nova/conf/workarounds.py index 7419f073b4..6c52eae8e5 100644 --- a/nova/conf/workarounds.py +++ b/nova/conf/workarounds.py @@ -402,6 +402,14 @@ Related options: * :oslo.config:option:`quota.driver` """), + cfg.BoolOpt('skip_cpu_compare_on_dest', + default=False, + help=""" +With the libvirt driver, during live migration, skip comparing guest CPU +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. +"""), ] diff --git a/nova/tests/unit/virt/libvirt/test_driver.py b/nova/tests/unit/virt/libvirt/test_driver.py index fd3d322b19..5632fcba86 100644 --- a/nova/tests/unit/virt/libvirt/test_driver.py +++ b/nova/tests/unit/virt/libvirt/test_driver.py @@ -10922,6 +10922,25 @@ class LibvirtConnTestCase(test.NoDBTestCase, '_create_shared_storage_test_file', return_value='fake') @mock.patch.object(libvirt_driver.LibvirtDriver, '_compare_cpu') + def test_check_can_live_migrate_guest_cpu_none_model_skip_compare( + self, mock_cpu, mock_test_file): + self.flags(group='workarounds', skip_cpu_compare_on_dest=True) + instance_ref = objects.Instance(**self.test_instance) + instance_ref.vcpu_model = test_vcpu_model.fake_vcpumodel + instance_ref.vcpu_model.model = None + drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), False) + compute_info = {'cpu_info': 'asdf', 'disk_available_least': 1} + drvr.check_can_live_migrate_destination( + self.context, instance_ref, compute_info, compute_info) + mock_cpu.assert_not_called() + + @mock.patch( + 'nova.network.neutron.API.has_port_binding_extension', + new=mock.Mock(return_value=False)) + @mock.patch.object(libvirt_driver.LibvirtDriver, + '_create_shared_storage_test_file', + return_value='fake') + @mock.patch.object(libvirt_driver.LibvirtDriver, '_compare_cpu') def test_check_can_live_migrate_dest_numa_lm( self, mock_cpu, mock_test_file, ): diff --git a/nova/virt/libvirt/driver.py b/nova/virt/libvirt/driver.py index 94e7b1945a..7c0abcb150 100644 --- a/nova/virt/libvirt/driver.py +++ b/nova/virt/libvirt/driver.py @@ -9338,15 +9338,16 @@ class LibvirtDriver(driver.ComputeDriver): disk_available_mb = ( (disk_available_gb * units.Ki) - CONF.reserved_host_disk_mb) - # Compare CPU - try: - if not instance.vcpu_model or not instance.vcpu_model.model: - source_cpu_info = src_compute_info['cpu_info'] - self._compare_cpu(None, source_cpu_info, instance) - else: - self._compare_cpu(instance.vcpu_model, None, instance) - except exception.InvalidCPUInfo as e: - raise exception.MigrationPreCheckError(reason=e) + if not CONF.workarounds.skip_cpu_compare_on_dest: + # Compare CPU + try: + if not instance.vcpu_model or not instance.vcpu_model.model: + source_cpu_info = src_compute_info['cpu_info'] + self._compare_cpu(None, source_cpu_info, instance) + else: + self._compare_cpu(instance.vcpu_model, None, instance) + except exception.InvalidCPUInfo as e: + raise exception.MigrationPreCheckError(reason=e) # Create file on storage, to be checked on source host filename = self._create_shared_storage_test_file(instance) diff --git a/releasenotes/notes/skip-compare-cpu-on-dest-6ae419ddd61fd0f8.yaml b/releasenotes/notes/skip-compare-cpu-on-dest-6ae419ddd61fd0f8.yaml new file mode 100644 index 0000000000..e7cd4041b1 --- /dev/null +++ b/releasenotes/notes/skip-compare-cpu-on-dest-6ae419ddd61fd0f8.yaml @@ -0,0 +1,24 @@ +--- +issues: + - | + Nova's use of libvirt's compareCPU() API served its purpose over the + years, but its design limitations break live migration in subtle + ways. For example, the compareCPU() API compares against the host + physical CPUID. Some of the features from this CPUID aren not + exposed by KVM, and then there are some features that KVM emulates + that are not in the host CPUID. The latter can cause bogus live + migration failures. + + With QEMU >=2.9 and libvirt >= 4.4.0, libvirt will do the right + thing in terms of CPU compatibility checks on the destination host + during live migration. Nova satisfies these minimum version + requirements by a good margin. So, this workaround provides a way to + skip the CPU comparison check on the destination host before + migrating a guest, and let libvirt handle it correctly. + + This workaround will be deprecated and removed once Nova replaces + the older libvirt APIs with their newer counterparts. The work is + being tracked via this `blueprint + cpu-selection-with-hypervisor-consideration`_. + + .. _blueprint cpu-selection-with-hypervisor-consideration: https://blueprints.launchpad.net/nova/+spec/cpu-selection-with-hypervisor-consideration |