Unskip test_rx_tx_queue_size

Previously, this test was skipped because it depended on a compute host
config that we did not set in CI. This patch adds a
[whitebox]/rx_queue_size config option to indicate what queue size is
configured on the compute hosts, gives it a sensible default in our
devstack plugin, makes test_rx_tx_queue_size use its value in the
test's assertion, and unskips the test. Woot. (The test itself also
needs a small fix in how it accesses the XML attribute).

Change-Id: I3cfe53dceb8801754b424ef7be71739a9b11c032

.zuul.yaml

@@ -88,6 +88,7 @@
                 cpu_models: kvm64
                 cpu_model_extra_flags: ssse3
                 virt_type: kvm
+                rx_queue_size: 1024
     group-vars:
         subnode:
             num_hugepages: 2048

devstack/plugin.sh

@@ -15,6 +15,7 @@ function configure {
     iniset $TEMPEST_CONFIG whitebox file_backed_memory_size $WHITEBOX_FILE_BACKED_MEMORY_SIZE
     iniset $TEMPEST_CONFIG whitebox cpu_model $WHITEBOX_CPU_MODEL
     iniset $TEMPEST_CONFIG whitebox cpu_model_extra_flags $WHITEBOX_CPU_MODEL_EXTRA_FLAGS
+    iniset $TEMPEST_CONFIG whitebox rx_queue_size $WHITEBOX_RX_QUEUE_SIZE
 
     iniset $TEMPEST_CONFIG whitebox-nova-compute config_path "$WHITEBOX_NOVA_COMPUTE_CONFIG_PATH"
     iniset $TEMPEST_CONFIG whitebox-nova-compute stop_command "$WHITEBOX_NOVA_COMPUTE_STOP_COMMAND"

devstack/settings

@@ -5,6 +5,7 @@ SMT_HOSTS=${SMT_HOSTS:-''}
 WHITEBOX_FILE_BACKED_MEMORY_SIZE=${WHITEBOX_FILE_BACKED_MEMORY_SIZE:-8192}
 WHITEBOX_CPU_MODEL=${WHITEBOX_CPU_MODEL:-kvm64}
 WHITEBOX_CPU_MODEL_EXTRA_FLAGS=${WHITEBOX_CPU_MODEL_EXTRA_FLAGS:-ssse3}
+WHITEBOX_RX_QUEUE_SIZE=${WHITEBOX_RX_QUEUE_SIZE:-1024}
 
 WHITEBOX_NOVA_COMPUTE_CONFIG_PATH=${WHITEBOX_NOVA_COMPUTE_CONFIG_PATH:-/etc/nova/nova-cpu.conf}
 WHITEBOX_NOVA_COMPUTE_STOP_COMMAND=${WHITEBOX_NOVA_COMPUTE_STOP_COMMAND:-'systemctl stop devstack@n-cpu'}

whitebox_tempest_plugin/api/compute/test_rx_tx_queue_size.py

@@ -12,13 +12,13 @@
 #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 #    License for the specific language governing permissions and limitations
 #    under the License.
-#
+
+import testtools
 
 from oslo_log import log as logging
 from tempest.common import waiters
 from tempest import config
 from tempest.lib.common.utils import data_utils
-from tempest.lib import decorators
 
 from whitebox_tempest_plugin.api.compute import base
 
@@ -67,17 +67,12 @@ class RxTxQueueSizeTest(base.BaseWhiteboxComputeTest):
                                        cls.server_id, "ACTIVE")
         cls.addClassResourceCleanup(cls.delete_server, cls.server_id)
 
-    # Required in /etc/nova/nova.conf
-    #    [libvirt]
-    #    rx_queue_size = 1024
-    # TODO(artom) We either need to refactor this to use the
-    # ServiceManager.config_option context manager, or remove this test
-    # altogether if it adds no value.
-    @decorators.skip_because(bug='2006820', bug_type='storyboard')
+    @testtools.skipUnless(CONF.whitebox.rx_queue_size,
+                          '`rx_queue_size` must be set')
     def test_rx_queue_size(self):
         domain = self.get_server_xml(self.server_id)
         driver = domain.find(
             "devices/interface[@type='bridge']/driver[@name='vhost']")
         self.assertEqual(
-            driver.attrib('rx_queue_size'), '1024',
+            driver.attrib['rx_queue_size'], str(CONF.whitebox.rx_queue_size),
             "Can't find interface with the proper rx_queue_size")

whitebox_tempest_plugin/config.py

@@ -109,7 +109,11 @@ general_opts = [
         default=None,
         help='The expected pmem size allocated to the instance. It requires '
              'an IEC supported unit of measurement, i.e. Kb, Mb, KB, GB, KiB, '
-             'GiB, etc. Example format 1GB, 4GiB, 100GB. ')
+             'GiB, etc. Example format 1GB, 4GiB, 100GB. '),
+    cfg.IntOpt(
+        'rx_queue_size',
+        help='The queue size set in the [libvirt]/rx_queue_size config option '
+             'on the compute hosts.')
 ]
 
 nova_compute_group = cfg.OptGroup(