Manage compute node that exposes no pci devices

Booting a VM with a pci device causes an exception when the host doesnt
have any assignable pci devices.
If a host doesnt expose any pci devices to nova, its pci_stats are set
to None. This causes an exception when the PciPassthroughFilter checks
if the host can support the pci requests.

Closes-Bug: #1435981
Change-Id: Ia9fbec9c7a3afa9b7ea73c43b21db0909a195a36

nova/scheduler/host_manager.py

@@ -213,11 +213,8 @@ class HostState(object):
         self.updated = compute.updated_at
         self.numa_topology = compute.numa_topology
         self.instance_numa_topology = None
-        if compute.pci_device_pools is not None:
-            self.pci_stats = pci_stats.PciDeviceStats(
-                compute.pci_device_pools)
-        else:
-            self.pci_stats = None
+        self.pci_stats = pci_stats.PciDeviceStats(
+            compute.pci_device_pools)
 
         # All virt drivers report host_ip
         self.host_ip = compute.host_ip

nova/tests/unit/scheduler/filters/test_pci_passthrough_filters.py

@@ -13,6 +13,7 @@
 import mock
 
 from nova import objects
+from nova.pci import stats
 from nova.scheduler.filters import pci_passthrough_filter
 from nova import test
 from nova.tests.unit.scheduler import fakes
@@ -65,3 +66,12 @@ class TestPCIPassthroughFilter(test.NoDBTestCase):
             attribute_dict={})
         self.assertRaises(AttributeError, self.filt_cls.host_passes,
                           host, filter_properties)
+
+    def test_pci_passthrough_no_pci_stats(self):
+        request = objects.InstancePCIRequest(count=1,
+            spec=[{'vendor_id': '8086'}])
+        requests = objects.InstancePCIRequests(requests=[request])
+        filter_properties = {'pci_requests': requests}
+        host = fakes.FakeHostState('host1', 'node1',
+            attribute_dict={'pci_stats': stats.PciDeviceStats()})
+        self.assertFalse(self.filt_cls.host_passes(host, filter_properties))

nova/tests/unit/scheduler/test_host_manager.py

@@ -824,7 +824,7 @@ class HostStateTestCase(test.NoDBTestCase):
 
         host = host_manager.HostState("fakehost", "fakenode")
         host.update_from_compute_node(compute)
-        self.assertIsNone(host.pci_stats)
+        self.assertEqual([], host.pci_stats.pools)
         self.assertEqual(hyper_ver_int, host.hypervisor_version)
 
     def test_stat_consumption_from_compute_node_rescue_unshelving(self):
@@ -860,7 +860,7 @@ class HostStateTestCase(test.NoDBTestCase):
         self.assertEqual(42, host.num_io_ops)
         self.assertEqual(10, len(host.stats))
 
-        self.assertIsNone(host.pci_stats)
+        self.assertEqual([], host.pci_stats.pools)
         self.assertEqual(hyper_ver_int, host.hypervisor_version)
 
     @mock.patch('nova.virt.hardware.get_host_numa_usage_from_instance')