[clark-laughlin, r=gnuoy]

This change allows the nova-compute charm to deploy on arm64 machines without requiring a different configuration to be used. To deploy nova-compute on arm64 requires 2 settings in nova.conf, which are not required for amd64:

libvirt_use_virtio_for_bridges = False
libvirt_disk_prefix = vd

Since juju configuration is specified at the service level, there is not a way to provide a separate configuration when deploying an amd64 unit and an arm64 unit -- preventing deployment of openstack with a mixture of arm64 and amd64 nova-compute nodes.

This change simply detects the machine architecture, and adds the two configuration settings to nova.conf when running on an arm64 (aarch64) machine. Behavior when running on other architectures is unchanged.

hooks/nova_compute_context.py

@@ -1,5 +1,5 @@
 import uuid
-
+import platform
 from charmhelpers.contrib.openstack import context
 from charmhelpers.core.host import service_running, service_start
 from charmhelpers.fetch import apt_install, filter_installed_packages
@@ -104,6 +104,9 @@ class NovaComputeLibvirtContext(context.OSContextGenerator):
             'listen_tls': 0,
         }
 
+        # get the processor architecture to use in the nova.conf template
+        ctxt['arch'] = platform.machine()
+
         # enable tcp listening if configured for live migration.
         if config('enable-live-migration'):
             ctxt['libvirtd_opts'] += ' -l'

templates/havana/nova.conf

@@ -13,7 +13,14 @@ logdir=/var/log/nova
 state_path=/var/lib/nova
 lock_path=/var/lock/nova
 force_dhcp_release=True
+
+{% if arch == 'aarch64' -%}
+libvirt_use_virtio_for_bridges=False
+libvirt_disk_prefix=vd
+{% else -%}
 libvirt_use_virtio_for_bridges=True
+{% endif -%}
+
 verbose=True
 use_syslog = {{ use_syslog }}
 ec2_private_dns_show_ip=True

templates/juno/nova.conf

@@ -13,7 +13,14 @@ logdir=/var/log/nova
 state_path=/var/lib/nova
 lock_path=/var/lock/nova
 force_dhcp_release=True
+
+{% if arch == 'aarch64' -%}
+libvirt_use_virtio_for_bridges=False
+libvirt_disk_prefix=vd
+{% else -%}
 libvirt_use_virtio_for_bridges=True
+{% endif -%}
+
 verbose=True
 use_syslog = {{ use_syslog }}
 ec2_private_dns_show_ip=True

templates/kilo/nova.conf

@@ -21,6 +21,11 @@ auth_strategy=keystone
 compute_driver=libvirt.LibvirtDriver
 my_ip = {{ host_ip }}
 
+{% if arch == 'aarch64' -%}
+libvirt_use_virtio_for_bridges=False
+libvirt_disk_prefix=vd
+{% endif -%}
+
 {% if console_vnc_type -%}
 vnc_enabled = True
 novnc_enabled = True

unit_tests/test_nova_compute_contexts.py

@@ -1,3 +1,5 @@
+import platform
+
 from mock import patch
 from test_utils import CharmTestCase
 
@@ -179,6 +181,7 @@ class NovaComputeContextTests(CharmTestCase):
 
         self.assertEqual(
             {'libvirtd_opts': '-d',
+             'arch': platform.machine(),
              'listen_tls': 0,
              'host_uuid': 'e46e530d-18ae-4a67-9ff0-e6e2ba7c60a7'}, libvirt())
 
@@ -190,6 +193,7 @@ class NovaComputeContextTests(CharmTestCase):
 
         self.assertEqual(
             {'libvirtd_opts': '-d -l',
+             'arch': platform.machine(),
              'listen_tls': 0,
              'host_uuid': 'e46e530d-18ae-4a67-9ff0-e6e2ba7c60a7'}, libvirt())
 
@@ -201,9 +205,10 @@ class NovaComputeContextTests(CharmTestCase):
 
         self.assertEqual(
             {'libvirtd_opts': '-d',
+             'disk_cachemodes': 'file=unsafe,block=none',
+             'arch': platform.machine(),
              'listen_tls': 0,
-             'host_uuid': 'e46e530d-18ae-4a67-9ff0-e6e2ba7c60a7',
-             'disk_cachemodes': 'file=unsafe,block=none'}, libvirt())
+             'host_uuid': 'e46e530d-18ae-4a67-9ff0-e6e2ba7c60a7'}, libvirt())
 
     @patch.object(context.NeutronComputeContext, 'network_manager')
     @patch.object(context.NeutronComputeContext, 'plugin')