Return vcpu pin set as set rather than list

The current implementation of the libvirt driver makes mixed assumptions
about the vcpu pin set returned from hardware.get_vcpu_pin_set(). Most
places in the code assume its a set and perform set operations on the
structure. However a few  places assume it's a list. Given the mixed
assumptions about the structure type, the existing code was trying
to perform set operations on a list.

This patch changes the get_vcpu_pin_set() method to return a set
rather than a list and handles any edge cases where consumers need
a list. It also updates any relevant unit tests accordingly.

Change-Id: I66d5cbc0e2d370d9d2d2ab2bad2c5b348bedba6c
Closes-Bug: 1372829

nova/tests/virt/test_hardware.py

@@ -57,7 +57,7 @@ class CpuSetTestCase(test.NoDBTestCase):
     def test_get_vcpu_pin_set(self):
         self.flags(vcpu_pin_set="1-3,5,^2")
         cpuset_ids = hw.get_vcpu_pin_set()
-        self.assertEqual([1, 3, 5], cpuset_ids)
+        self.assertEqual(set([1, 3, 5]), cpuset_ids)
 
     def test_parse_cpu_spec_none_returns_none(self):
         self.flags(vcpu_pin_set=None)

nova/virt/hardware.py

@@ -39,7 +39,7 @@ LOG = logging.getLogger(__name__)
 def get_vcpu_pin_set():
     """Parsing vcpu_pin_set config.
 
-    Returns a list of pcpu ids can be used by instances.
+    Returns a set of pcpu ids can be used by instances.
     """
     if not CONF.vcpu_pin_set:
         return None
@@ -48,7 +48,7 @@ def get_vcpu_pin_set():
     if not cpuset_ids:
         raise exception.Invalid(_("No CPUs available after parsing %r") %
                                 CONF.vcpu_pin_set)
-    return sorted(cpuset_ids)
+    return cpuset_ids
 
 
 def parse_cpu_spec(spec):

nova/virt/libvirt/driver.py

@@ -4538,7 +4538,7 @@ class LibvirtDriver(driver.ComputeDriver):
             return self._vcpu_total
 
         available_ids = hardware.get_vcpu_pin_set()
-        if available_ids[-1] >= total_pcpus:
+        if sorted(available_ids)[-1] >= total_pcpus:
             raise exception.Invalid(_("Invalid vcpu_pin_set config, "
                                       "out of hypervisor cpu range."))
         self._vcpu_total = len(available_ids)