Add support for the 'cpu_models' option in nova.conf

Since OpenStack Train release the 'cpu_models' config option
has superseded the 'cpu_model' config option in the nova.conf.
This patch adds support for the new 'cpu_models' allowing a user
to provide a comma separated list of supported, named CPU models.

This patch also inclused unit test for the cpu_mode='custom'.

Closes-bug: #2025914
Change-Id: I30328abc07d3304f1bfb67c81360fb5229214c97

config.yaml

@@ -395,6 +395,27 @@ options:
       Set to a named libvirt CPU model (see names listed in
       /usr/share/libvirt/cpu_map.xml). Only has effect if cpu_mode='custom' and
       virt_type='kvm|qemu'.
+      .
+      Starting from the Train release this option is deprecated and
+      has been superseded by the 'cpu-models' option. This option will be
+      silently ignored if the 'cpu-models' option is non-empty.
+  cpu-models:
+    type: string
+    default:
+    description: |
+      An ordered, comma separated, list of the CPU models supported by the host.
+      The models on the list must be ordered according to the features they
+      support. The less advanced models must precede more advanced, feature
+      rich, models.
+      .
+      Example: 'SandyBridge,IvyBridge,Haswell,Broadwell'
+      .
+      CPU models are listed in:
+        * /usr/share/libvirt/cpu_map.xml (libvirt version < 4.7.0)
+        * /usr/share/libvirt/cpu_map/*.xml (libvirt version >= 4.7.0)
+      .
+      This option only has effect if cpu_mode='custom' and
+      virt_type='kvm|qemu'.
   cpu-model-extra-flags:
     type: string
     default:

hooks/nova_compute_context.py

@@ -278,7 +278,9 @@ class NovaComputeLibvirtContext(context.OSContextGenerator):
         elif ctxt['arch'] == 's390x':
             ctxt['cpu_mode'] = 'none'
 
-        if config('cpu-model'):
+        if config('cpu-models'):
+            ctxt['cpu_models'] = config('cpu-models')
+        elif config('cpu-model'):
             ctxt['cpu_model'] = config('cpu-model')
 
         if config('cpu-model-extra-flags'):

templates/train/nova.conf

@@ -287,6 +287,9 @@ inject_partition = {{ inject_partition }}
 {% if cpu_mode -%}
 cpu_mode = {{ cpu_mode }}
 {% endif -%}
+{% if cpu_models -%}
+cpu_models = {{ cpu_models }}
+{% endif -%}
 {% if cpu_model -%}
 cpu_model = {{ cpu_model }}
 {% endif -%}

templates/yoga/nova.conf

@@ -270,6 +270,9 @@ inject_partition = {{ inject_partition }}
 {% if cpu_mode -%}
 cpu_mode = {{ cpu_mode }}
 {% endif -%}
+{% if cpu_models -%}
+cpu_models = {{ cpu_models }}
+{% endif -%}
 {% if cpu_model -%}
 cpu_model = {{ cpu_model }}
 {% endif -%}

unit_tests/test_nova_compute_contexts.py

@@ -842,6 +842,41 @@ class NovaComputeContextTests(CharmTestCase):
         self.assertEqual(libvirt()['cpu_mode'],
                          'none')
 
+    @patch.object(context.uuid, 'uuid4')
+    def test_libvirt_cpu_mode_custom_model(self, mock_uuid):
+        self.test_config.set('cpu-mode', 'custom')
+        self.test_config.set('cpu-model', 'Broadwell')
+        self.lsb_release.return_value = {'DISTRIB_CODENAME': 'bionic'}
+        mock_uuid.return_value = 'e46e530d-18ae-4a67-9ff0-e6e2ba7c60a7'
+        libvirt = context.NovaComputeLibvirtContext()
+
+        self.assertEqual(libvirt()['cpu_mode'], 'custom')
+        self.assertEqual(libvirt()['cpu_model'], 'Broadwell')
+
+        # should be ignored
+        self.test_config.set('cpu-mode', 'host-model')
+        self.test_config.set('cpu-model', 'Haswell')
+        libvirt = context.NovaComputeLibvirtContext()
+        self.assertNotIn('cpu-model', libvirt())
+
+    @patch.object(context.uuid, 'uuid4')
+    def test_libvirt_cpu_mode_custom_models(self, mock_uuid):
+        self.test_config.set('cpu-mode', 'custom')
+        self.test_config.set('cpu-models',
+                             'SandyBridge,IvyBridge,Haswell,Broadwell')
+        self.lsb_release.return_value = {'DISTRIB_CODENAME': 'bionic'}
+        mock_uuid.return_value = 'e46e530d-18ae-4a67-9ff0-e6e2ba7c60a7'
+        libvirt = context.NovaComputeLibvirtContext()
+
+        self.assertEqual(libvirt()['cpu_mode'], 'custom')
+        self.assertEqual(libvirt()['cpu_models'],
+                         'SandyBridge,IvyBridge,Haswell,Broadwell')
+
+        # should be ignored
+        self.test_config.set('cpu-model', 'Haswell')
+        libvirt = context.NovaComputeLibvirtContext()
+        self.assertNotIn('cpu_model', libvirt())
+
     @patch.object(context, 'platform')
     @patch.object(context.uuid, 'uuid4')
     def test_libvirt_cpu_mode_aarch64(self, mock_uuid, mock_platform):