libvirt: Add ppc to supported arch for NUMA

This patch includes the ppc64/ppc64le architectures to the list
of host architectures that support NUMA via the libvirt driver.

This change is for the PowerPC based servers that use the libvirt
driver. This also introduces the minimum libvirt version needed
for PowerPC to support NUMA from Nova.

Also note, that in order to retain the unit test that excluded
PPC from the NUMA supported architectures, an arbitrary choice
of architecture is made (S390) - that is not a part of the list
that supports NUMA.

Change-Id: I51dd3e160153b40072a04095e9bf3f15abd74252
Closes-Bug: #1516578

nova/tests/unit/virt/libvirt/test_driver.py

@@ -1584,6 +1584,19 @@ class LibvirtConnTestCase(test.NoDBTestCase):
             exception.NUMATopologyUnsupported,
             None)
 
+    def test_get_guest_config_numa_old_version_libvirt_ppc(self):
+        self.flags(virt_type='kvm', group='libvirt')
+
+        self._test_get_guest_config_numa_unsupported(
+            versionutils.convert_version_to_int(
+                libvirt_driver.MIN_LIBVIRT_NUMA_VERSION_PPC) - 1,
+            versionutils.convert_version_to_int(
+                libvirt_driver.MIN_QEMU_NUMA_HUGEPAGE_VERSION),
+            host.HV_DRIVER_QEMU,
+            arch.PPC64LE,
+            exception.NUMATopologyUnsupported,
+            None)
+
     def test_get_guest_config_numa_bad_version_libvirt(self):
         self.flags(virt_type='kvm', group='libvirt')
 
@@ -1633,13 +1646,12 @@ class LibvirtConnTestCase(test.NoDBTestCase):
             versionutils.convert_version_to_int(
                 libvirt_driver.MIN_QEMU_NUMA_HUGEPAGE_VERSION),
             host.HV_DRIVER_QEMU,
-            arch.PPC64,
+            arch.S390,
             exception.NUMATopologyUnsupported,
             None)
 
     def test_get_guest_config_numa_xen(self):
         self.flags(virt_type='xen', group='libvirt')
-
         self._test_get_guest_config_numa_unsupported(
             versionutils.convert_version_to_int(
                 libvirt_driver.MIN_LIBVIRT_NUMA_VERSION),

nova/virt/libvirt/driver.py

@@ -381,6 +381,8 @@ MIN_QEMU_DISCARD_VERSION = (1, 6, 0)
 # this the scheduler cannot make guaranteed decisions, as the
 # guest placement may not match what was requested
 MIN_LIBVIRT_NUMA_VERSION = (1, 2, 7)
+# PowerPC based hosts that support NUMA using libvirt
+MIN_LIBVIRT_NUMA_VERSION_PPC = (1, 2, 19)
 # Versions of libvirt with known NUMA topology issues
 # See bug #1449028
 BAD_LIBVIRT_NUMA_VERSIONS = [(1, 2, 9, 2)]
@@ -4912,13 +4914,18 @@ class LibvirtDriver(driver.ComputeDriver):
                     self._bad_libvirt_numa_version_warn = True
                 return False
 
-        supported_archs = [arch.I686, arch.X86_64]
+        support_matrix = {(arch.I686, arch.X86_64): MIN_LIBVIRT_NUMA_VERSION,
+                          (arch.PPC64,
+                           arch.PPC64LE): MIN_LIBVIRT_NUMA_VERSION_PPC}
         caps = self._host.get_capabilities()
-
-        return ((caps.host.cpu.arch in supported_archs) and
-                self._host.has_min_version(MIN_LIBVIRT_NUMA_VERSION,
-                                           MIN_QEMU_NUMA_HUGEPAGE_VERSION,
-                                           host.HV_DRIVER_QEMU))
+        is_supported = False
+        for archs, libvirt_ver in support_matrix.items():
+            if ((caps.host.cpu.arch in archs) and
+                    self._host.has_min_version(libvirt_ver,
+                                               MIN_QEMU_NUMA_HUGEPAGE_VERSION,
+                                               host.HV_DRIVER_QEMU)):
+                is_supported = True
+        return is_supported
 
     def _has_hugepage_support(self):
         # This means that the host can support multiple values for the size

releasenotes/notes/1516578-628b417b372f4f0f.yaml

@@ -0,0 +1,14 @@
+---
+features:
+  - |
+    Enables NUMA topology reporting on PowerPC architecture
+    from the libvirt driver in Nova but with a caveat as mentioned below.
+    NUMA cell affinity and dedicated cpu pinning
+    code assumes that the host operating system is exposed to threads.
+    PowerPC based hosts use core based scheduling for processes.
+    Due to this, the cores on the PowerPC architecture are treated as
+    threads. Since cores are always less than or equal
+    to the threads on a system, this leads to non-optimal resource usage
+    while pinning. This feature is supported from libvirt version 1.2.19
+    for PowerPC.
+