Add configuration for cpu model flags

Change-Id: Ia26d0f2d4f540dd5b35743d0348aa6e2b8ab1954
Closes-Bug: #1750829

config.yaml

@@ -259,6 +259,11 @@ 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'.
+  cpu-model-extra-flags:
+    type: string
+    default:
+    description: |
+      Space delimited list of specific CPU flags for libvirt.
   # Storage config
   libvirt-image-backend:
     type: string

hooks/nova_compute_context.py

@@ -210,6 +210,10 @@ class NovaComputeLibvirtContext(context.OSContextGenerator):
         if config('cpu-model'):
             ctxt['cpu_model'] = config('cpu-model')
 
+        if config('cpu-model-extra-flags'):
+            ctxt['cpu_model_extra_flags'] = ', '.join(
+                config('cpu-model-extra-flags').split(' '))
+
         if config('hugepages'):
             ctxt['hugepages'] = True
             ctxt['kvm_hugepages'] = 1

templates/ocata/nova.conf

@@ -184,6 +184,9 @@ cpu_mode = {{ cpu_mode }}
 {% if cpu_model -%}
 cpu_model = {{ cpu_model }}
 {% endif -%}
+{% if cpu_model_extra_flags %}
+cpu_model_extra_flags = {{ cpu_model_extra_flags }}
+{% endif %}
 {% if libvirt_images_type -%}
 images_type = {{ libvirt_images_type }}
 {% endif -%}

templates/pike/nova.conf

@@ -187,6 +187,9 @@ cpu_mode = {{ cpu_mode }}
 {% if cpu_model -%}
 cpu_model = {{ cpu_model }}
 {% endif -%}
+{% if cpu_model_extra_flags %}
+cpu_model_extra_flags = {{ cpu_model_extra_flags }}
+{% endif %}
 {% if libvirt_images_type -%}
 images_type = {{ libvirt_images_type }}
 {% endif -%}

unit_tests/test_nova_compute_contexts.py

@@ -501,6 +501,14 @@ class NovaComputeContextTests(CharmTestCase):
         self.assertEqual(context.nova_metadata_requirement(),
                          (True, None))
 
+    def test_nova_compute_extra_flags(self):
+        self.test_config.set('cpu-model-extra-flags', 'pcid vmx pdpe1gb')
+        self.lsb_release.return_value = {'DISTRIB_CODENAME': 'bionic'}
+        libvirt = context.NovaComputeLibvirtContext()
+
+        self.assertEqual(libvirt()['cpu_model_extra_flags'],
+                         'pcid, vmx, pdpe1gb')
+
 
 class SerialConsoleContextTests(CharmTestCase):