Merge "Allow enabling cpu_power_management with 0 dedicated CPUs"

nova/tests/functional/libvirt/test_power_manage.py

@@ -108,14 +108,13 @@ class PowerManagementTests(PowerManagementTestsBase):
         cpu_dedicated_set = hardware.get_cpu_dedicated_set()
         self._assert_cpu_set_state(cpu_dedicated_set, expected='offline')
 
-    def test_hardstop_compute_service_if_wrong_opt(self):
+    def test_compute_service_starts_with_power_management_and_zero_pcpu(self):
         self.flags(cpu_dedicated_set=None, cpu_shared_set=None,
                    group='compute')
         self.flags(vcpu_pin_set=None)
         self.flags(cpu_power_management=True, group='libvirt')
-        self.assertRaises(exception.InvalidConfiguration,
-                          self.start_compute, host_info=self.host_info,
-                                              hostname='compute2')
+        self.start_compute(host_info=self.host_info, hostname='compute2')
+        # NOTE(gibi): we test that no exception is raised by start_compute
 
     def test_create_server(self):
         server = self._create_server(

nova/tests/unit/virt/libvirt/cpu/test_api.py

@@ -182,11 +182,14 @@ class TestAPI(test.NoDBTestCase):
         api.power_down_all_dedicated_cpus()
         mock_offline.assert_not_called()
 
-    def test_power_down_all_dedicated_cpus_wrong_config(self):
+    @mock.patch.object(core, 'set_offline')
+    def test_power_down_all_dedicated_cpus_no_dedicated_cpus_configured(
+        self, mock_offline
+    ):
         self.flags(cpu_power_management=True, group='libvirt')
         self.flags(cpu_dedicated_set=None, group='compute')
-        self.assertRaises(exception.InvalidConfiguration,
-                          api.power_down_all_dedicated_cpus)
+        api.power_down_all_dedicated_cpus()
+        mock_offline.assert_not_called()
 
     @mock.patch.object(core, 'get_governor')
     @mock.patch.object(core, 'get_online')
@@ -233,3 +236,10 @@ class TestAPI(test.NoDBTestCase):
         mock_warning.assert_called_once_with(
             'CPU0 is in cpu_dedicated_set, but it is not eligible for '
             'state management and will be ignored')
+
+    def test_validate_all_dedicated_cpus_no_cpu(self):
+        self.flags(cpu_power_management=True, group='libvirt')
+        self.flags(cpu_dedicated_set=None, group='compute')
+        api.validate_all_dedicated_cpus()
+        # no assert we want to make sure the validation won't raise if
+        # no dedicated cpus are configured

nova/virt/hardware.py

@@ -78,7 +78,7 @@ def get_cpu_dedicated_set():
 
 def get_cpu_dedicated_set_nozero():
     """Return cpu_dedicated_set without CPU0, if present"""
-    return get_cpu_dedicated_set() - {0}
+    return (get_cpu_dedicated_set() or set()) - {0}
 
 
 def get_cpu_shared_set():

nova/virt/libvirt/cpu/api.py

@@ -118,14 +118,6 @@ def power_down(instance: objects.Instance) -> None:
 def power_down_all_dedicated_cpus() -> None:
     if not CONF.libvirt.cpu_power_management:
         return
-    if (CONF.libvirt.cpu_power_management and
-        not CONF.compute.cpu_dedicated_set
-    ):
-        msg = _("'[compute]/cpu_dedicated_set' is mandatory to be set if "
-                "'[libvirt]/cpu_power_management' is set."
-                "Please provide the CPUs that can be pinned or don't use the "
-                "power management if you only use shared CPUs.")
-        raise exception.InvalidConfiguration(msg)
 
     cpu_dedicated_set = hardware.get_cpu_dedicated_set_nozero() or set()
     for pcpu in cpu_dedicated_set:

releasenotes/notes/bug-2043707-power-management-no-pcpu-28dd7d07d0473ea2.yaml

@@ -0,0 +1,11 @@
+---
+fixes:
+  - |
+    Relaxed the config option checking of the cpu_power_management feature of
+    the libvirt driver. The nova-compute service will start with
+    [libvirt]cpu_power_management=True and an empty [compute]cpu_dedicated_set
+    configuration. The power management is still only applied to dedicated CPUs.
+    So the above configuration only allowed to ensure that cpu_power_management
+    can be enabled independently for configuring cpu_dedicated_set during
+    deployment.
+