1 files changed, 78 insertions, 0 deletions
diff --git a/nova/virt/libvirt/cpu/core.py b/nova/virt/libvirt/cpu/core.py
new file mode 100644
index 0000000000..782f028fee
--- /dev/null
+++ b/nova/virt/libvirt/cpu/core.py
@@ -0,0 +1,78 @@
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import os
+import typing as ty
+
+from oslo_log import log as logging
+
+from nova import exception
+from nova import filesystem
+import nova.privsep
+from nova.virt import hardware
+
+LOG = logging.getLogger(__name__)
+
+AVAILABLE_PATH = '/sys/devices/system/cpu/present'
+
+CPU_PATH_TEMPLATE = '/sys/devices/system/cpu/cpu%(core)s'
+
+
+def get_available_cores() -> ty.Set[int]:
+    cores = filesystem.read_sys(AVAILABLE_PATH)
+    return hardware.parse_cpu_spec(cores) if cores else set()
+
+
+def exists(core: int) -> bool:
+    return core in get_available_cores()
+
+
+def gen_cpu_path(core: int) -> str:
+    if not exists(core):
+        LOG.warning('Unable to access CPU: %s', core)
+        raise ValueError('CPU: %(core)s does not exist', core)
+    return CPU_PATH_TEMPLATE % {'core': core}
+
+
+def get_online(core: int) -> bool:
+    try:
+        online = filesystem.read_sys(
+            os.path.join(gen_cpu_path(core), 'online')).strip()
+    except exception.FileNotFound:
+        # The online file may not exist if we haven't written it yet.
+        # By default, this means that the CPU is online.
+        online = '1'
+    return online == '1'
+
+
+@nova.privsep.sys_admin_pctxt.entrypoint
+def set_online(core: int) -> bool:
+    filesystem.write_sys(os.path.join(gen_cpu_path(core), 'online'), data='1')
+    return get_online(core)
+
+
+def set_offline(core: int) -> bool:
+    filesystem.write_sys(os.path.join(gen_cpu_path(core), 'online'), data='0')
+    return not get_online(core)
+
+
+def get_governor(core: int) -> str:
+    return filesystem.read_sys(
+        os.path.join(gen_cpu_path(core), 'cpufreq/scaling_governor')).strip()
+
+
+@nova.privsep.sys_admin_pctxt.entrypoint
+def set_governor(core: int, governor: str) -> str:
+    filesystem.write_sys(
+        os.path.join(gen_cpu_path(core), 'cpufreq/scaling_governor'),
+        data=governor)
+    return get_governor(core)