virt/hardware: Check for threads when "required"

The 'require' case "requires" the presence of hardware threads on a
host. At present, this check is done using the NUMATopology filter.
Unfortunately, this means that if this filter is disabled then
instances can be scheduled on invalid hosts. Resolve this by adding a
new check to be run when hosts are actually scheduling.

Change-Id: Ia9e4784e02ca9ce7a3d81c962b95bee100f6db42
Closes-bug: #1550269

nova/tests/unit/virt/test_hardware.py

@@ -2263,6 +2263,22 @@ class CPUPinningCellTestCase(test.NoDBTestCase, _CPUPinningTestCaseBase):
         got_pinning = {x: x for x in range(0, 4)}
         self.assertEqual(got_pinning, inst_pin.cpu_pinning)
 
+    def test_get_pinning_require_policy_no_siblings(self):
+        host_pin = objects.NUMACell(
+                id=0,
+                cpuset=set([0, 1, 2, 3, 4, 5, 6, 7]),
+                memory=4096, memory_usage=0,
+                pinned_cpus=set([]),
+                siblings=[],
+                mempages=[])
+        inst_pin = objects.InstanceNUMACell(
+                cpuset=set([0, 1, 2, 3]),
+                memory=2048,
+                cpu_policy=fields.CPUAllocationPolicy.DEDICATED,
+                cpu_thread_policy=fields.CPUThreadAllocationPolicy.REQUIRE)
+        inst_pin = hw._numa_fit_instance_cell_with_pinning(host_pin, inst_pin)
+        self.assertIsNone(inst_pin)
+
     def test_get_pinning_require_policy_too_few_siblings(self):
         host_pin = objects.NUMACell(
                 id=0,

nova/virt/hardware.py

@@ -25,7 +25,7 @@ import six
 import nova.conf
 from nova import context
 from nova import exception
-from nova.i18n import _
+from nova.i18n import _, _LI
 from nova import objects
 from nova.objects import fields
 from nova.objects import instance as obj_instance
@@ -842,6 +842,13 @@ def _numa_fit_instance_cell_with_pinning(host_cell, instance_cell):
             host_cell.free_siblings, instance_cell, host_cell.id,
             max(map(len, host_cell.siblings)))
     else:
+        if (instance_cell.cpu_thread_policy ==
+                fields.CPUThreadAllocationPolicy.REQUIRE):
+            LOG.info(_LI("Host does not support hyperthreading or "
+                         "hyperthreading is disabled, but 'require' "
+                         "threads policy was requested."))
+            return
+
         # Straightforward to pin to available cpus when there is no
         # hyperthreading on the host
         free_cpus = [set([cpu]) for cpu in host_cell.free_cpus]