adding compute/cpu_shared_set option

For Rocky, Nova introduced compute/cpu_shared_set and libvirt driver
uses that option to specify set of pCPUs which will be used to put
emulator threads on. So guest vCPUs can be pinned on pCPUs which will
be entirely dedicated for them.

Change-Id: I88b2afda67a91266f21d2c870a76646262488db2
Closes-Bug: 1806434
Signed-off-by: Sahid Orentino Ferdjaoui <sahid.ferdjaoui@canonical.com>

config.yaml

@@ -187,6 +187,14 @@ options:
       Sets vcpu_pin_set option in nova.conf which defines which pcpus that
       instance vcpus can or cannot use. For example '^0,^2' to reserve two
       cpus for the host.
+  cpu-shared-set:
+    type: string
+    default:
+    description: |
+      Sets compute/cpu_shared_set option in nova.conf defines which
+      physical CPUs will be used for best-effort guest vCPU resources.
+      Currently only used by libvirt driver to place guest emulator threads
+      when hw:emulator_threads_policy:share is set.
   virtio-net-tx-queue-size:
     type: int
     default:

hooks/nova_compute_context.py

@@ -247,6 +247,9 @@ class NovaComputeLibvirtContext(context.OSContextGenerator):
         if config('vcpu-pin-set'):
             ctxt['vcpu_pin_set'] = config('vcpu-pin-set')
 
+        if config('cpu-shared-set'):
+            ctxt['cpu_shared_set'] = config('cpu-shared-set')
+
         if config('virtio-net-tx-queue-size'):
             ctxt['virtio_net_tx_queue_size'] = (
                 config('virtio-net-tx-queue-size'))

templates/rocky/nova.conf

@@ -264,3 +264,9 @@ disable_libvirt_livesnapshot = False
 {% include "parts/section-serial-console" %}
 
 {% include "parts/section-placement" %}
+
+[compute]
+{% if cpu_shared_set -%}
+cpu_shared_set = {{ cpu_shared_set }}
+{% endif -%}
+

unit_tests/test_nova_compute_contexts.py

@@ -398,6 +398,7 @@ class NovaComputeContextTests(CharmTestCase):
         self.test_config.set('pci-passthrough-whitelist', 'mypcidevices')
         self.test_config.set('virtio-net-tx-queue-size', 512)
         self.test_config.set('virtio-net-rx-queue-size', 1024)
+        self.test_config.set('cpu-shared-set', "4-12,^8,15")
         libvirt = context.NovaComputeLibvirtContext()
 
         self.assertEqual(
@@ -414,7 +415,8 @@ class NovaComputeContextTests(CharmTestCase):
              'force_raw_images': True,
              'pci_passthrough_whitelist': 'mypcidevices',
              'virtio_net_tx_queue_size': 512,
-             'virtio_net_rx_queue_size': 1024}, libvirt())
+             'virtio_net_rx_queue_size': 1024,
+             'cpu_shared_set': "4-12,^8,15"}, libvirt())
 
     def test_ksm_configs(self):
         self.lsb_release.return_value = {'DISTRIB_CODENAME': 'lucid'}