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host.py
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host.py
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# Copyright 2010 United States Government as represented by the
# Administrator of the National Aeronautics and Space Administration.
# All Rights Reserved.
# Copyright (c) 2010 Citrix Systems, Inc.
# Copyright (c) 2011 Piston Cloud Computing, Inc
# Copyright (c) 2012 University Of Minho
# (c) Copyright 2013 Hewlett-Packard Development Company, L.P.
#
# 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.
"""
Manages information about the host OS and hypervisor.
This class encapsulates a connection to the libvirt
daemon and provides certain higher level APIs around
the raw libvirt API. These APIs are then used by all
the other libvirt related classes
"""
from collections import defaultdict
import fnmatch
import glob
import inspect
from lxml import etree
import operator
import os
import queue
import socket
import threading
import typing as ty
from eventlet import greenio
from eventlet import greenthread
from eventlet import patcher
from eventlet import tpool
from oslo_log import log as logging
from oslo_serialization import jsonutils
from oslo_utils import excutils
from oslo_utils import importutils
from oslo_utils import strutils
from oslo_utils import units
from oslo_utils import versionutils
from nova.compute import utils as compute_utils
import nova.conf
from nova import context as nova_context
from nova import exception
from nova.i18n import _
from nova.objects import fields
from nova.pci import utils as pci_utils
from nova import rpc
from nova import utils
from nova.virt import event as virtevent
from nova.virt.libvirt import config as vconfig
from nova.virt.libvirt import event as libvirtevent
from nova.virt.libvirt import guest as libvirt_guest
from nova.virt.libvirt import migration as libvirt_migrate
from nova.virt.libvirt import utils as libvirt_utils
import nova.virt.node # noqa
if ty.TYPE_CHECKING:
import libvirt
else:
libvirt = None
LOG = logging.getLogger(__name__)
native_socket = patcher.original('socket')
native_threading = patcher.original("threading")
native_Queue = patcher.original("queue")
CONF = nova.conf.CONF
# This list is for libvirt hypervisor drivers that need special handling.
# This is *not* the complete list of supported hypervisor drivers.
HV_DRIVER_QEMU = "QEMU"
SEV_KERNEL_PARAM_FILE = '/sys/module/kvm_amd/parameters/sev'
# These are taken from the spec
# https://github.com/qemu/qemu/blob/v5.2.0/docs/interop/firmware.json
QEMU_FIRMWARE_DESCRIPTOR_PATHS = [
'/usr/share/qemu/firmware',
'/etc/qemu/firmware',
# we intentionally ignore '$XDG_CONFIG_HOME/qemu/firmware'
]
def _get_loaders():
if not any(
os.path.exists(path) for path in QEMU_FIRMWARE_DESCRIPTOR_PATHS
):
msg = _("Failed to locate firmware descriptor files")
raise exception.InternalError(msg)
_loaders = []
for path in QEMU_FIRMWARE_DESCRIPTOR_PATHS:
if not os.path.exists(path):
continue
for spec_path in sorted(glob.glob(f'{path}/*.json')):
with open(spec_path, 'rb') as fh:
spec = jsonutils.load(fh)
_loaders.append(spec)
return _loaders
class Host(object):
def __init__(self, uri, read_only=False,
conn_event_handler=None,
lifecycle_event_handler=None):
global libvirt
if libvirt is None:
libvirt = importutils.import_module('libvirt')
self._uri = uri
self._read_only = read_only
self._initial_connection = True
self._conn_event_handler = conn_event_handler
self._conn_event_handler_queue: queue.Queue[ty.Callable] = (
queue.Queue())
self._lifecycle_event_handler = lifecycle_event_handler
self._caps = None
self._domain_caps = None
self._hostname = None
self._node_uuid = None
self._wrapped_conn = None
self._wrapped_conn_lock = threading.Lock()
self._event_queue: ty.Optional[queue.Queue[ty.Callable]] = None
self._events_delayed = {}
# Note(toabctl): During a reboot of a domain, STOPPED and
# STARTED events are sent. To prevent shutting
# down the domain during a reboot, delay the
# STOPPED lifecycle event some seconds.
self._lifecycle_delay = 15
self._initialized = False
self._libvirt_proxy_classes = self._get_libvirt_proxy_classes(libvirt)
self._libvirt_proxy = self._wrap_libvirt_proxy(libvirt)
self._loaders: ty.Optional[ty.List[dict]] = None
# A number of features are conditional on support in the hardware,
# kernel, QEMU, and/or libvirt. These are determined on demand and
# memoized by various properties below
self._supports_amd_sev: ty.Optional[bool] = None
self._supports_uefi: ty.Optional[bool] = None
self._supports_secure_boot: ty.Optional[bool] = None
self._has_hyperthreading: ty.Optional[bool] = None
@staticmethod
def _get_libvirt_proxy_classes(libvirt_module):
"""Return a tuple for tpool.Proxy's autowrap argument containing all
public vir* classes defined by the libvirt module.
"""
# Get a list of (name, class) tuples of libvirt classes
classes = inspect.getmembers(libvirt_module, inspect.isclass)
# Return a list of just the vir* classes, filtering out libvirtError
# and any private globals pointing at private internal classes.
return tuple([cls[1] for cls in classes if cls[0].startswith("vir")])
def _wrap_libvirt_proxy(self, obj):
"""Return an object wrapped in a tpool.Proxy using autowrap appropriate
for the libvirt module.
"""
# libvirt is not pure python, so eventlet monkey patching doesn't work
# on it. Consequently long-running libvirt calls will not yield to
# eventlet's event loop, starving all other greenthreads until
# completion. eventlet's tpool.Proxy handles this situation for us by
# executing proxied calls in a native thread.
return tpool.Proxy(obj, autowrap=self._libvirt_proxy_classes)
def _native_thread(self):
"""Receives async events coming in from libvirtd.
This is a native thread which runs the default
libvirt event loop implementation. This processes
any incoming async events from libvirtd and queues
them for later dispatch. This thread is only
permitted to use libvirt python APIs, and the
driver.queue_event method. In particular any use
of logging is forbidden, since it will confuse
eventlet's greenthread integration
"""
while True:
libvirt.virEventRunDefaultImpl()
def _dispatch_thread(self):
"""Dispatches async events coming in from libvirtd.
This is a green thread which waits for events to
arrive from the libvirt event loop thread. This
then dispatches the events to the compute manager.
"""
while True:
self._dispatch_events()
def _conn_event_thread(self):
"""Dispatches async connection events"""
# NOTE(mdbooth): This thread doesn't need to jump through the same
# hoops as _dispatch_thread because it doesn't interact directly
# with the libvirt native thread.
while True:
self._dispatch_conn_event()
def _dispatch_conn_event(self):
# NOTE(mdbooth): Splitting out this loop looks redundant, but it
# means we can easily dispatch events synchronously from tests and
# it isn't completely awful.
handler = self._conn_event_handler_queue.get()
try:
handler()
except Exception:
LOG.exception('Exception handling connection event')
finally:
self._conn_event_handler_queue.task_done()
@staticmethod
def _event_device_removed_callback(conn, dom, dev, opaque):
"""Receives device removed events from libvirt.
NB: this method is executing in a native thread, not
an eventlet coroutine. It can only invoke other libvirt
APIs, or use self._queue_event(). Any use of logging APIs
in particular is forbidden.
"""
self = opaque
uuid = dom.UUIDString()
self._queue_event(libvirtevent.DeviceRemovedEvent(uuid, dev))
@staticmethod
def _event_device_removal_failed_callback(conn, dom, dev, opaque):
"""Receives device removed events from libvirt.
NB: this method is executing in a native thread, not
an eventlet coroutine. It can only invoke other libvirt
APIs, or use self._queue_event(). Any use of logging APIs
in particular is forbidden.
"""
self = opaque
uuid = dom.UUIDString()
self._queue_event(libvirtevent.DeviceRemovalFailedEvent(uuid, dev))
@staticmethod
def _event_lifecycle_callback(conn, dom, event, detail, opaque):
"""Receives lifecycle events from libvirt.
NB: this method is executing in a native thread, not
an eventlet coroutine. It can only invoke other libvirt
APIs, or use self._queue_event(). Any use of logging APIs
in particular is forbidden.
"""
self = opaque
uuid = dom.UUIDString()
transition = None
if event == libvirt.VIR_DOMAIN_EVENT_STOPPED:
transition = virtevent.EVENT_LIFECYCLE_STOPPED
elif event == libvirt.VIR_DOMAIN_EVENT_STARTED:
transition = virtevent.EVENT_LIFECYCLE_STARTED
elif event == libvirt.VIR_DOMAIN_EVENT_SUSPENDED:
if detail == libvirt.VIR_DOMAIN_EVENT_SUSPENDED_POSTCOPY:
transition = virtevent.EVENT_LIFECYCLE_POSTCOPY_STARTED
elif detail == libvirt.VIR_DOMAIN_EVENT_SUSPENDED_MIGRATED:
# VIR_DOMAIN_EVENT_SUSPENDED_MIGRATED is also sent when live
# migration of the guest fails, so we cannot simply rely
# on the event itself but need to check if the job itself was
# successful.
# NOTE(mriedem): The job check logic here is copied from
# LibvirtDriver._live_migration_monitor.
guest = libvirt_guest.Guest(dom)
info = guest.get_job_info()
if info.type == libvirt.VIR_DOMAIN_JOB_NONE:
# Either still running, or failed or completed,
# lets untangle the mess.
info.type = libvirt_migrate.find_job_type(
guest, instance=None, logging_ok=False)
if info.type == libvirt.VIR_DOMAIN_JOB_COMPLETED:
transition = virtevent.EVENT_LIFECYCLE_MIGRATION_COMPLETED
else:
# Failed or some other status we don't know about, so just
# opt to report the guest is paused.
transition = virtevent.EVENT_LIFECYCLE_PAUSED
else:
transition = virtevent.EVENT_LIFECYCLE_PAUSED
elif event == libvirt.VIR_DOMAIN_EVENT_RESUMED:
transition = virtevent.EVENT_LIFECYCLE_RESUMED
if transition is not None:
self._queue_event(virtevent.LifecycleEvent(uuid, transition))
def _close_callback(self, conn, reason, opaque):
close_info = {'conn': conn, 'reason': reason}
self._queue_event(close_info)
@staticmethod
def _test_connection(conn):
try:
conn.getLibVersion()
return True
except libvirt.libvirtError as e:
if (e.get_error_code() in (libvirt.VIR_ERR_SYSTEM_ERROR,
libvirt.VIR_ERR_INTERNAL_ERROR) and
e.get_error_domain() in (libvirt.VIR_FROM_REMOTE,
libvirt.VIR_FROM_RPC)):
LOG.debug('Connection to libvirt broke')
return False
raise
@staticmethod
def _connect_auth_cb(creds, opaque):
if len(creds) == 0:
return 0
raise exception.InternalError(
_("Can not handle authentication request for %d credentials")
% len(creds))
def _connect(self, uri, read_only):
auth = [[libvirt.VIR_CRED_AUTHNAME,
libvirt.VIR_CRED_ECHOPROMPT,
libvirt.VIR_CRED_REALM,
libvirt.VIR_CRED_PASSPHRASE,
libvirt.VIR_CRED_NOECHOPROMPT,
libvirt.VIR_CRED_EXTERNAL],
Host._connect_auth_cb,
None]
flags = 0
if read_only:
flags = libvirt.VIR_CONNECT_RO
return self._libvirt_proxy.openAuth(uri, auth, flags)
def _queue_event(self, event):
"""Puts an event on the queue for dispatch.
This method is called by the native event thread to
put events on the queue for later dispatch by the
green thread. Any use of logging APIs is forbidden.
"""
if self._event_queue is None:
return
# Queue the event...
self._event_queue.put(event)
# ...then wakeup the green thread to dispatch it
c = ' '.encode()
self._event_notify_send.write(c)
self._event_notify_send.flush()
def _dispatch_events(self):
"""Wait for & dispatch events from native thread
Blocks until native thread indicates some events
are ready. Then dispatches all queued events.
"""
# Wait to be notified that there are some
# events pending
try:
_c = self._event_notify_recv.read(1)
assert _c
except ValueError:
return # will be raised when pipe is closed
# Process as many events as possible without
# blocking
last_close_event = None
# required for mypy
if self._event_queue is None:
return
while not self._event_queue.empty():
try:
event_type = ty.Union[
virtevent.InstanceEvent, ty.Mapping[str, ty.Any]]
event: event_type = self._event_queue.get(block=False)
if issubclass(type(event), virtevent.InstanceEvent):
# call possibly with delay
self._event_emit_delayed(event)
elif 'conn' in event and 'reason' in event:
last_close_event = event
except native_Queue.Empty:
pass
if last_close_event is None:
return
conn = last_close_event['conn']
# get_new_connection may already have disabled the host,
# in which case _wrapped_conn is None.
with self._wrapped_conn_lock:
if conn == self._wrapped_conn:
reason = str(last_close_event['reason'])
msg = _("Connection to libvirt lost: %s") % reason
self._wrapped_conn = None
self._queue_conn_event_handler(False, msg)
def _event_emit_delayed(self, event):
"""Emit events - possibly delayed."""
def event_cleanup(gt, *args, **kwargs):
"""Callback function for greenthread. Called
to cleanup the _events_delayed dictionary when an event
was called.
"""
event = args[0]
self._events_delayed.pop(event.uuid, None)
# Cleanup possible delayed stop events.
if event.uuid in self._events_delayed.keys():
self._events_delayed[event.uuid].cancel()
self._events_delayed.pop(event.uuid, None)
LOG.debug("Removed pending event for %s due to event", event.uuid)
if (isinstance(event, virtevent.LifecycleEvent) and
event.transition == virtevent.EVENT_LIFECYCLE_STOPPED):
# Delay STOPPED event, as they may be followed by a STARTED
# event in case the instance is rebooting
id_ = greenthread.spawn_after(self._lifecycle_delay,
self._event_emit, event)
self._events_delayed[event.uuid] = id_
# add callback to cleanup self._events_delayed dict after
# event was called
id_.link(event_cleanup, event)
else:
self._event_emit(event)
def _event_emit(self, event):
if self._lifecycle_event_handler is not None:
self._lifecycle_event_handler(event)
def _init_events_pipe(self):
"""Create a self-pipe for the native thread to synchronize on.
This code is taken from the eventlet tpool module, under terms
of the Apache License v2.0.
"""
self._event_queue = native_Queue.Queue()
try:
rpipe, wpipe = os.pipe()
self._event_notify_send = greenio.GreenPipe(wpipe, 'wb', 0)
self._event_notify_recv = greenio.GreenPipe(rpipe, 'rb', 0)
except (ImportError, NotImplementedError):
# This is Windows compatibility -- use a socket instead
# of a pipe because pipes don't really exist on Windows.
sock = native_socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.bind(('localhost', 0))
sock.listen(50)
csock = native_socket.socket(socket.AF_INET, socket.SOCK_STREAM)
csock.connect(('localhost', sock.getsockname()[1]))
nsock, addr = sock.accept()
self._event_notify_send = nsock.makefile('wb', 0)
gsock = greenio.GreenSocket(csock)
self._event_notify_recv = gsock.makefile('rb', 0)
def _init_events(self):
"""Initializes the libvirt events subsystem.
This requires running a native thread to provide the
libvirt event loop integration. This forwards events
to a green thread which does the actual dispatching.
"""
self._init_events_pipe()
LOG.debug("Starting native event thread")
self._event_thread = native_threading.Thread(
target=self._native_thread)
self._event_thread.daemon = True
self._event_thread.start()
LOG.debug("Starting green dispatch thread")
utils.spawn(self._dispatch_thread)
def _get_new_connection(self):
# call with _wrapped_conn_lock held
LOG.debug('Connecting to libvirt: %s', self._uri)
# This will raise an exception on failure
wrapped_conn = self._connect(self._uri, self._read_only)
try:
LOG.debug("Registering for lifecycle events %s", self)
wrapped_conn.domainEventRegisterAny(
None,
libvirt.VIR_DOMAIN_EVENT_ID_LIFECYCLE,
self._event_lifecycle_callback,
self)
wrapped_conn.domainEventRegisterAny(
None,
libvirt.VIR_DOMAIN_EVENT_ID_DEVICE_REMOVED,
self._event_device_removed_callback,
self)
wrapped_conn.domainEventRegisterAny(
None,
libvirt.VIR_DOMAIN_EVENT_ID_DEVICE_REMOVAL_FAILED,
self._event_device_removal_failed_callback,
self)
except Exception as e:
LOG.warning("URI %(uri)s does not support events: %(error)s",
{'uri': self._uri, 'error': e})
try:
LOG.debug("Registering for connection events: %s", str(self))
wrapped_conn.registerCloseCallback(self._close_callback, None)
except libvirt.libvirtError as e:
LOG.warning("URI %(uri)s does not support connection"
" events: %(error)s",
{'uri': self._uri, 'error': e})
return wrapped_conn
def _queue_conn_event_handler(self, *args, **kwargs):
if self._conn_event_handler is None:
return
def handler():
return self._conn_event_handler(*args, **kwargs)
self._conn_event_handler_queue.put(handler)
def _get_connection(self):
# multiple concurrent connections are protected by _wrapped_conn_lock
with self._wrapped_conn_lock:
# Drop the existing connection if it is not usable
if (self._wrapped_conn is not None and
not self._test_connection(self._wrapped_conn)):
self._wrapped_conn = None
# Connection was previously up, and went down
self._queue_conn_event_handler(
False, _('Connection to libvirt lost'))
if self._wrapped_conn is None:
try:
# This will raise if it fails to get a connection
self._wrapped_conn = self._get_new_connection()
except Exception as ex:
with excutils.save_and_reraise_exception():
# If we previously had a connection and it went down,
# we generated a down event for that above.
# We also want to generate a down event for an initial
# failure, which won't be handled above.
if self._initial_connection:
self._queue_conn_event_handler(
False,
_('Failed to connect to libvirt: %(msg)s') %
{'msg': ex})
finally:
self._initial_connection = False
self._queue_conn_event_handler(True, None)
return self._wrapped_conn
def get_connection(self):
"""Returns a connection to the hypervisor
This method should be used to create and return a well
configured connection to the hypervisor.
:returns: a libvirt.virConnect object
"""
try:
conn = self._get_connection()
except libvirt.libvirtError as ex:
LOG.exception("Connection to libvirt failed: %s", ex)
payload = {'ip': CONF.my_ip, 'method': '_connect', 'reason': ex}
ctxt = nova_context.get_admin_context()
rpc.get_notifier('compute').error(ctxt,
'compute.libvirt.error',
payload)
compute_utils.notify_about_libvirt_connect_error(
ctxt, ip=CONF.my_ip, exception=ex)
raise exception.HypervisorUnavailable()
return conn
@staticmethod
def _libvirt_error_handler(context, err):
# Just ignore instead of default outputting to stderr.
pass
def initialize(self):
if self._initialized:
return
# NOTE(dkliban): Error handler needs to be registered before libvirt
# connection is used for the first time. Otherwise, the
# handler does not get registered.
libvirt.registerErrorHandler(self._libvirt_error_handler, None)
libvirt.virEventRegisterDefaultImpl()
self._init_events()
LOG.debug("Starting connection event dispatch thread")
utils.spawn(self._conn_event_thread)
self._initialized = True
def _version_check(self, lv_ver=None, hv_ver=None, hv_type=None,
op=operator.lt):
"""Check libvirt version, hypervisor version, and hypervisor type
:param hv_type: hypervisor driver from the top of this file.
"""
conn = self.get_connection()
try:
if lv_ver is not None:
libvirt_version = conn.getLibVersion()
if op(libvirt_version,
versionutils.convert_version_to_int(lv_ver)):
return False
if hv_ver is not None:
hypervisor_version = conn.getVersion()
if op(hypervisor_version,
versionutils.convert_version_to_int(hv_ver)):
return False
if hv_type is not None:
hypervisor_type = conn.getType()
if hypervisor_type != hv_type:
return False
return True
except Exception:
return False
def has_min_version(self, lv_ver=None, hv_ver=None, hv_type=None):
return self._version_check(
lv_ver=lv_ver, hv_ver=hv_ver, hv_type=hv_type, op=operator.lt)
def has_version(self, lv_ver=None, hv_ver=None, hv_type=None):
return self._version_check(
lv_ver=lv_ver, hv_ver=hv_ver, hv_type=hv_type, op=operator.ne)
def get_guest(self, instance):
"""Retrieve libvirt guest object for an instance.
All libvirt error handling should be handled in this method and
relevant nova exceptions should be raised in response.
:param instance: a nova.objects.Instance object
:returns: a nova.virt.libvirt.Guest object
:raises exception.InstanceNotFound: The domain was not found
:raises exception.InternalError: A libvirt error occurred
"""
return libvirt_guest.Guest(self._get_domain(instance))
def _get_domain(self, instance):
"""Retrieve libvirt domain object for an instance.
All libvirt error handling should be handled in this method and
relevant nova exceptions should be raised in response.
:param instance: a nova.objects.Instance object
:returns: a libvirt.Domain object
:raises exception.InstanceNotFound: The domain was not found
:raises exception.InternalError: A libvirt error occurred
"""
try:
conn = self.get_connection()
return conn.lookupByUUIDString(instance.uuid)
except libvirt.libvirtError as ex:
error_code = ex.get_error_code()
if error_code == libvirt.VIR_ERR_NO_DOMAIN:
raise exception.InstanceNotFound(instance_id=instance.uuid)
msg = (_('Error from libvirt while looking up %(instance_name)s: '
'[Error Code %(error_code)s] %(ex)s') %
{'instance_name': instance.name,
'error_code': error_code,
'ex': ex})
raise exception.InternalError(msg)
def list_guests(self, only_running=True):
"""Get a list of Guest objects for nova instances
:param only_running: True to only return running instances
See method "list_instance_domains" for more information.
:returns: list of Guest objects
"""
domains = self.list_instance_domains(only_running=only_running)
return [libvirt_guest.Guest(dom) for dom in domains]
def list_instance_domains(self, only_running=True):
"""Get a list of libvirt.Domain objects for nova instances
:param only_running: True to only return running instances
Query libvirt to a get a list of all libvirt.Domain objects
that correspond to nova instances. If the only_running parameter
is true this list will only include active domains, otherwise
inactive domains will be included too.
:returns: list of libvirt.Domain objects
"""
flags = libvirt.VIR_CONNECT_LIST_DOMAINS_ACTIVE
if not only_running:
flags = flags | libvirt.VIR_CONNECT_LIST_DOMAINS_INACTIVE
# listAllDomains() returns <list of virDomain>, not <virDomain>, so
# tpool.Proxy's autowrap won't catch it. We need to wrap the
# contents of the list we return.
alldoms = (self._wrap_libvirt_proxy(dom)
for dom in self.get_connection().listAllDomains(flags))
doms = []
for dom in alldoms:
doms.append(dom)
return doms
def get_available_cpus(self):
"""Get the set of CPUs that exist on the host.
:returns: set of CPUs, raises libvirtError on error
"""
cpus, cpu_map, online = self.get_connection().getCPUMap()
return {cpu for cpu in range(cpus)}
def get_online_cpus(self):
"""Get the set of CPUs that are online on the host
:returns: set of online CPUs, raises libvirtError on error
"""
cpus, cpu_map, online = self.get_connection().getCPUMap()
online_cpus = set()
for cpu in range(cpus):
if cpu_map[cpu]:
online_cpus.add(cpu)
return online_cpus
def get_cpu_model_names(self):
"""Get the cpu models based on host CPU arch
:returns: a list of cpu models which supported by the given CPU arch
"""
arch = self.get_capabilities().host.cpu.arch
return self.get_connection().getCPUModelNames(arch)
@staticmethod
def _log_host_capabilities(xmlstr):
# NOTE(mriedem): This looks a bit weird but we do this so we can stub
# out this method in unit/functional test runs since the xml string is
# big and it can cause subunit parsing to fail (see bug 1813147).
LOG.info("Libvirt host capabilities %s", xmlstr)
def get_capabilities(self):
"""Returns the host capabilities information
Returns an instance of config.LibvirtConfigCaps representing
the capabilities of the host.
Note: The result is cached in the member attribute _caps.
:returns: a config.LibvirtConfigCaps object
"""
if self._caps:
return self._caps
xmlstr = self.get_connection().getCapabilities()
self._log_host_capabilities(xmlstr)
self._caps = vconfig.LibvirtConfigCaps()
self._caps.parse_str(xmlstr)
# NOTE(mriedem): Don't attempt to get baseline CPU features
# if libvirt can't determine the host cpu model.
if (
hasattr(libvirt, 'VIR_CONNECT_BASELINE_CPU_EXPAND_FEATURES') and
self._caps.host.cpu.model is not None
):
try:
xml_str = self._caps.host.cpu.to_xml()
if isinstance(xml_str, bytes):
xml_str = xml_str.decode('utf-8')
# NOTE(kevinz): The baseline CPU info on Aarch64 will not
# include any features. So on Aarch64, we use the original
# features from LibvirtConfigCaps.
if self._caps.host.cpu.arch != fields.Architecture.AARCH64:
features = self.get_connection().baselineCPU(
[xml_str],
libvirt.VIR_CONNECT_BASELINE_CPU_EXPAND_FEATURES)
if features:
cpu = vconfig.LibvirtConfigCPU()
cpu.parse_str(features)
self._caps.host.cpu.features = cpu.features
except libvirt.libvirtError as ex:
error_code = ex.get_error_code()
if error_code == libvirt.VIR_ERR_NO_SUPPORT:
LOG.warning(
"URI %(uri)s does not support full set of host "
"capabilities: %(error)s",
{'uri': self._uri, 'error': ex})
else:
raise
return self._caps
def get_domain_capabilities(self):
"""Returns the capabilities you can request when creating a
domain (VM) with that hypervisor, for various combinations of
architecture and machine type.
In this context the fuzzy word "hypervisor" implies QEMU
binary, libvirt itself and the host config. libvirt provides
this in order that callers can determine what the underlying
emulator and/or libvirt is capable of, prior to creating a domain
(for instance via virDomainCreateXML or virDomainDefineXML).
However nova needs to know the capabilities much earlier, when
the host's compute service is first initialised, in order that
placement decisions can be made across many compute hosts.
Therefore this is expected to be called during the init_host()
phase of the driver lifecycle rather than just before booting
an instance.
This causes an additional complication since the Python
binding for this libvirt API call requires the architecture
and machine type to be provided. So in order to gain a full
picture of the hypervisor's capabilities, technically we need
to call it with the right parameters, once for each
(architecture, machine_type) combination which we care about.
However the libvirt experts have advised us that in practice
the domain capabilities do not (yet, at least) vary enough
across machine types to justify the cost of calling
getDomainCapabilities() once for every single (architecture,
machine_type) combination. In particular, SEV support isn't
reported per-machine type, and since there are usually many
machine types, we heed the advice of the experts that it's
typically sufficient to call it once per host architecture:
https://bugzilla.redhat.com/show_bug.cgi?id=1683471#c7
However, that's not quite sufficient in the context of nova,
because SEV guests typically require a q35 machine type, as do
KVM/QEMU guests that want Secure Boot, whereas the current
default machine type for x86_64 is 'pc'. So we need results
from the getDomainCapabilities API for at least those two.
Fortunately we can take advantage of the results from the
getCapabilities API which marks selected machine types as
canonical, e.g.:
<machine canonical='pc-i440fx-2.11' maxCpus='255'>pc</machine>
<machine canonical='pc-q35-2.11' maxCpus='288'>q35</machine>
So for now, we call getDomainCapabilities for these canonical
machine types of each architecture, plus for the
architecture's default machine type, if that is not one of the
canonical types.
Future domain capabilities might report SEV in a more
fine-grained manner, and we also expect to use this method to
detect other features, such as for gracefully handling machine
types and potentially for detecting OVMF binaries. Therefore
we memoize the results of the API calls in a nested dict where
the top-level keys are architectures, and second-level keys
are machine types, in order to allow easy expansion later.
Whenever libvirt/QEMU are updated, cached domCapabilities
would get outdated (because QEMU will contain new features and
the capabilities will vary). However, this should not be a
problem here, because when libvirt/QEMU gets updated, the
nova-compute agent also needs restarting, at which point the
memoization will vanish because it's not persisted to disk.
Note: The result is cached in the member attribute
_domain_caps.
:returns: a nested dict of dicts which maps architectures to
machine types to instances of config.LibvirtConfigDomainCaps
representing the domain capabilities of the host for that arch and
machine type: ``{arch: machine_type: LibvirtConfigDomainCaps}{``
"""
if self._domain_caps:
return self._domain_caps
domain_caps: ty.Dict = defaultdict(dict)
caps = self.get_capabilities()
virt_type = CONF.libvirt.virt_type
for guest in caps.guests:
arch = guest.arch
domain = guest.domains.get(virt_type, guest.default_domain)
for machine_type in self._get_machine_types(arch, domain):
# It is expected that if there are multiple <guest>
# elements, each will have a different architecture;
# for example, on x86 hosts one <guest> will contain
# <arch name='i686'> and one will contain <arch
# name='x86_64'>. But it doesn't hurt to add a safety
# net to avoid needlessly calling libvirt's API more
# times than we need.
if machine_type and machine_type in domain_caps[arch]:
continue
self._add_to_domain_capabilities(domain.emulator, arch,
domain_caps, machine_type,
virt_type)
# NOTE(aspiers): Use a temporary variable to update the
# instance variable atomically, otherwise if some API
# calls succeeded and then one failed, we might
# accidentally memoize a partial result.
self._domain_caps = domain_caps
return self._domain_caps
def _get_machine_types(self, arch, domain):
"""Get the machine types for this architecture for which we need to
call getDomainCapabilities, i.e. the canonical machine types,
and the default machine type (if it's not one of the canonical
machine types).
See the docstring for get_domain_capabilities() for an explanation
of why we choose this set of machine types.
"""
# NOTE(aspiers): machine_type could be None here if nova
# doesn't have a default machine type for this architecture.
# See _add_to_domain_capabilities() below for how this is handled.
mtypes = set([libvirt_utils.get_default_machine_type(arch)])
mtypes.update(domain.aliases.keys())
LOG.debug("Getting domain capabilities for %(arch)s via "
"machine types: %(mtypes)s",
{'arch': arch, 'mtypes': mtypes})
return mtypes
def _add_to_domain_capabilities(self, emulator_bin, arch, domain_caps,
machine_type, virt_type):
# NOTE(aspiers): machine_type could be None here if nova
# doesn't have a default machine type for this architecture.
# In that case we pass a machine_type of None to the libvirt
# API and rely on it choosing a sensible default which will be
# returned in the <machine> element. It could also be an
# alias like 'pc' rather than a full machine type.
#
# NOTE(kchamart): Prior to libvirt v4.7.0 libvirt picked its
# default machine type for x86, 'pc', as reported by QEMU's
# default. From libvirt v4.7.0 onwards, libvirt _explicitly_
# declared the "preferred" default for x86 as 'pc' (and
# appropriate values for other architectures), and only uses
# QEMU's reported default (whatever that may be) if 'pc' does
# not exist. This was done "to isolate applications from
# hypervisor changes that may cause incompatibilities" --
# i.e. if, or when, QEMU changes its default machine type to
# something else. Refer to this libvirt commit:
#
# https://libvirt.org/git/?p=libvirt.git;a=commit;h=26cfb1a3
try:
cap_obj = self._get_domain_capabilities(
emulator_bin=emulator_bin, arch=arch,
machine_type=machine_type, virt_type=virt_type)
except libvirt.libvirtError as ex:
# NOTE(sean-k-mooney): This can happen for several
# reasons, but one common example is if you have
# multiple QEMU emulators installed and you set
# virt-type=kvm. In this case any non-native emulator,
# e.g. AArch64 on an x86 host, will (correctly) raise
# an exception as KVM cannot be used to accelerate CPU
# instructions for non-native architectures.
error_code = ex.get_error_code()
LOG.debug(
"Error from libvirt when retrieving domain capabilities "
"for arch %(arch)s / virt_type %(virt_type)s / "
"machine_type %(mach_type)s: "
"[Error Code %(error_code)s]: %(exception)s",
{'arch': arch, 'virt_type': virt_type,
'mach_type': machine_type, 'error_code': error_code,
'exception': ex})
# Remove archs added by default dict lookup when checking
# if the machine type has already been recoded.