ifdown: Use new methods to unconfigure NICs

[ganeti-local] / lib / hypervisor / hv_kvm.py

#
#

# Copyright (C) 2008, 2009, 2010, 2011, 2012, 2013 Google Inc.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301, USA.


"""KVM hypervisor

"""

import errno
import os
import os.path
import re
import tempfile
import time
import logging
import pwd
import struct
import fcntl
import shutil
import socket
import stat
import StringIO
from bitarray import bitarray
try:
  import affinity   # pylint: disable=F0401
except ImportError:
  affinity = None
try:
  import fdsend   # pylint: disable=F0401
except ImportError:
  fdsend = None

from ganeti import utils
from ganeti import constants
from ganeti import errors
from ganeti import serializer
from ganeti import objects
from ganeti import uidpool
from ganeti import ssconf
from ganeti import netutils
from ganeti import pathutils
from ganeti.hypervisor import hv_base
from ganeti.utils import wrapper as utils_wrapper


_KVM_NETWORK_SCRIPT = pathutils.CONF_DIR + "/kvm-ifup-custom"
_KVM_START_PAUSED_FLAG = "-S"

# TUN/TAP driver constants, taken from <linux/if_tun.h>
# They are architecture-independent and already hardcoded in qemu-kvm source,
# so we can safely include them here.
TUNSETIFF = 0x400454ca
TUNGETIFF = 0x800454d2
TUNGETFEATURES = 0x800454cf
IFF_TAP = 0x0002
IFF_NO_PI = 0x1000
IFF_VNET_HDR = 0x4000

#: SPICE parameters which depend on L{constants.HV_KVM_SPICE_BIND}
_SPICE_ADDITIONAL_PARAMS = frozenset([
  constants.HV_KVM_SPICE_IP_VERSION,
  constants.HV_KVM_SPICE_PASSWORD_FILE,
  constants.HV_KVM_SPICE_LOSSLESS_IMG_COMPR,
  constants.HV_KVM_SPICE_JPEG_IMG_COMPR,
  constants.HV_KVM_SPICE_ZLIB_GLZ_IMG_COMPR,
  constants.HV_KVM_SPICE_STREAMING_VIDEO_DETECTION,
  constants.HV_KVM_SPICE_USE_TLS,
  ])

# Constant bitarray that reflects to a free pci slot
# Use it with bitarray.search()
_AVAILABLE_PCI_SLOT = bitarray("0")

# below constants show the format of runtime file
# the nics are in second possition, while the disks in 4th (last)
# moreover disk entries are stored as a list of in tuples
# (L{objects.Disk}, link_name)
_KVM_NICS_RUNTIME_INDEX = 1
_KVM_DISKS_RUNTIME_INDEX = 3
_DEVICE_RUNTIME_INDEX = {
  constants.HOTPLUG_TARGET_DISK: _KVM_DISKS_RUNTIME_INDEX,
  constants.HOTPLUG_TARGET_NIC: _KVM_NICS_RUNTIME_INDEX
  }
_FIND_RUNTIME_ENTRY = {
  constants.HOTPLUG_TARGET_NIC:
    lambda nic, kvm_nics: [n for n in kvm_nics if n.uuid == nic.uuid],
  constants.HOTPLUG_TARGET_DISK:
    lambda disk, kvm_disks: [(d, l) for (d, l) in kvm_disks
                             if d.uuid == disk.uuid]
  }
_RUNTIME_DEVICE = {
  constants.HOTPLUG_TARGET_NIC: lambda d: d,
  constants.HOTPLUG_TARGET_DISK: lambda (d, e): d
  }
_RUNTIME_ENTRY = {
  constants.HOTPLUG_TARGET_NIC: lambda d, e: d,
  constants.HOTPLUG_TARGET_DISK: lambda d, e: (d, e)
  }


def _GenerateDeviceKVMId(dev_type, dev, idx=None):
  """Helper function to generate a unique device name used by KVM

  QEMU monitor commands use names to identify devices. Here we use their pci
  slot and a part of their UUID to name them. dev.pci might be None for old
  devices in the cluster.

  @type dev_type: sting
  @param dev_type: device type of param dev
  @type dev: L{objects.Disk} or L{objects.NIC}
  @param dev: the device object for which we generate a kvm name
  @raise errors.HotplugError: in case a device has no pci slot (old devices)

  """

  # proper device id - available in latest Ganeti versions
  if dev.pci and dev.uuid:
    return "%s-%s-pci-%d" % (dev_type.lower(), dev.uuid.split("-")[0], dev.pci)

  # dummy device id - returned only to _GenerateKVMBlockDevicesOptions
  # This enables -device option for paravirtual disk_type
  if idx is not None:
    return "%s-%d" % (dev_type.lower(), idx)

  raise errors.HotplugError("Hotplug is not supported for devices"
                            " without UUID or PCI info")


def _UpdatePCISlots(dev, pci_reservations):
  """Update pci configuration for a stopped instance

  If dev has a pci slot then reserve it, else find first available
  in pci_reservations bitarray. It acts on the same objects passed
  as params so there is no need to return anything.

  @type dev: L{objects.Disk} or L{objects.NIC}
  @param dev: the device object for which we update its pci slot
  @type pci_reservations: bitarray
  @param pci_reservations: existing pci reservations for an instance
  @raise errors.HotplugError: in case an instance has all its slot occupied

  """
  if dev.pci:
    free = dev.pci
  else: # pylint: disable=E1103
    [free] = pci_reservations.search(_AVAILABLE_PCI_SLOT, 1)
    if not free:
      raise errors.HypervisorError("All PCI slots occupied")
    dev.pci = int(free)

  pci_reservations[free] = True


def _GetExistingDeviceInfo(dev_type, device, runtime):
  """Helper function to get an existing device inside the runtime file

  Used when an instance is running. Load kvm runtime file and search
  for a device based on its type and uuid.

  @type dev_type: sting
  @param dev_type: device type of param dev
  @type device: L{objects.Disk} or L{objects.NIC}
  @param device: the device object for which we generate a kvm name
  @type runtime: tuple (cmd, nics, hvparams, disks)
  @param runtime: the runtime data to search for the device
  @raise errors.HotplugError: in case the requested device does not
    exist (e.g. device has been added without --hotplug option) or
    device info has not pci slot (e.g. old devices in the cluster)

  """
  index = _DEVICE_RUNTIME_INDEX[dev_type]
  found = _FIND_RUNTIME_ENTRY[dev_type](device, runtime[index])
  if not found:
    raise errors.HotplugError("Cannot find runtime info for %s with UUID %s" %
                              (dev_type, device.uuid))

  return found[0]


def _UpgradeSerializedRuntime(serialized_runtime):
  """Upgrade runtime data

  Remove any deprecated fields or change the format of the data.
  The runtime files are not upgraded when Ganeti is upgraded, so the required
  modification have to be performed here.

  @type serialized_runtime: string
  @param serialized_runtime: raw text data read from actual runtime file
  @return: (cmd, nic dicts, hvparams, bdev dicts)
  @rtype: tuple

  """
  loaded_runtime = serializer.Load(serialized_runtime)
  kvm_cmd, serialized_nics, hvparams = loaded_runtime[:3]
  if len(loaded_runtime) >= 4:
    serialized_disks = loaded_runtime[3]
  else:
    serialized_disks = []

  for nic in serialized_nics:
    # Add a dummy uuid slot if an pre-2.8 NIC is found
    if "uuid" not in nic:
      nic["uuid"] = utils.NewUUID()

  return kvm_cmd, serialized_nics, hvparams, serialized_disks


def _AnalyzeSerializedRuntime(serialized_runtime):
  """Return runtime entries for a serialized runtime file

  @type serialized_runtime: string
  @param serialized_runtime: raw text data read from actual runtime file
  @return: (cmd, nics, hvparams, bdevs)
  @rtype: tuple

  """
  kvm_cmd, serialized_nics, hvparams, serialized_disks = \
    _UpgradeSerializedRuntime(serialized_runtime)
  kvm_nics = [objects.NIC.FromDict(snic) for snic in serialized_nics]
  kvm_disks = [(objects.Disk.FromDict(sdisk), link)
               for sdisk, link in serialized_disks]

  return (kvm_cmd, kvm_nics, hvparams, kvm_disks)


def _GetTunFeatures(fd, _ioctl=fcntl.ioctl):
  """Retrieves supported TUN features from file descriptor.

  @see: L{_ProbeTapVnetHdr}

  """
  req = struct.pack("I", 0)
  try:
    buf = _ioctl(fd, TUNGETFEATURES, req)
  except EnvironmentError, err:
    logging.warning("ioctl(TUNGETFEATURES) failed: %s", err)
    return None
  else:
    (flags, ) = struct.unpack("I", buf)
    return flags


def _ProbeTapVnetHdr(fd, _features_fn=_GetTunFeatures):
  """Check whether to enable the IFF_VNET_HDR flag.

  To do this, _all_ of the following conditions must be met:
   1. TUNGETFEATURES ioctl() *must* be implemented
   2. TUNGETFEATURES ioctl() result *must* contain the IFF_VNET_HDR flag
   3. TUNGETIFF ioctl() *must* be implemented; reading the kernel code in
      drivers/net/tun.c there is no way to test this until after the tap device
      has been created using TUNSETIFF, and there is no way to change the
      IFF_VNET_HDR flag after creating the interface, catch-22! However both
      TUNGETIFF and TUNGETFEATURES were introduced in kernel version 2.6.27,
      thus we can expect TUNGETIFF to be present if TUNGETFEATURES is.

   @type fd: int
   @param fd: the file descriptor of /dev/net/tun

  """
  flags = _features_fn(fd)

  if flags is None:
    # Not supported
    return False

  result = bool(flags & IFF_VNET_HDR)

  if not result:
    logging.warning("Kernel does not support IFF_VNET_HDR, not enabling")

  return result


def _OpenTap(vnet_hdr=True):
  """Open a new tap device and return its file descriptor.

  This is intended to be used by a qemu-type hypervisor together with the -net
  tap,fd=<fd> command line parameter.

  @type vnet_hdr: boolean
  @param vnet_hdr: Enable the VNET Header
  @return: (ifname, tapfd)
  @rtype: tuple

  """
  try:
    tapfd = os.open("/dev/net/tun", os.O_RDWR)
  except EnvironmentError:
    raise errors.HypervisorError("Failed to open /dev/net/tun")

  flags = IFF_TAP | IFF_NO_PI

  if vnet_hdr and _ProbeTapVnetHdr(tapfd):
    flags |= IFF_VNET_HDR

  # The struct ifreq ioctl request (see netdevice(7))
  ifr = struct.pack("16sh", "", flags)

  try:
    res = fcntl.ioctl(tapfd, TUNSETIFF, ifr)
  except EnvironmentError, err:
    raise errors.HypervisorError("Failed to allocate a new TAP device: %s" %
                                 err)

  # Get the interface name from the ioctl
  ifname = struct.unpack("16sh", res)[0].strip("\x00")
  return (ifname, tapfd)


class QmpMessage:
  """QEMU Messaging Protocol (QMP) message.

  """
  def __init__(self, data):
    """Creates a new QMP message based on the passed data.

    """
    if not isinstance(data, dict):
      raise TypeError("QmpMessage must be initialized with a dict")

    self.data = data

  def __getitem__(self, field_name):
    """Get the value of the required field if present, or None.

    Overrides the [] operator to provide access to the message data,
    returning None if the required item is not in the message
    @return: the value of the field_name field, or None if field_name
             is not contained in the message

    """
    return self.data.get(field_name, None)

  def __setitem__(self, field_name, field_value):
    """Set the value of the required field_name to field_value.

    """
    self.data[field_name] = field_value

  @staticmethod
  def BuildFromJsonString(json_string):
    """Build a QmpMessage from a JSON encoded string.

    @type json_string: str
    @param json_string: JSON string representing the message
    @rtype: L{QmpMessage}
    @return: a L{QmpMessage} built from json_string

    """
    # Parse the string
    data = serializer.LoadJson(json_string)
    return QmpMessage(data)

  def __str__(self):
    # The protocol expects the JSON object to be sent as a single line.
    return serializer.DumpJson(self.data)

  def __eq__(self, other):
    # When comparing two QmpMessages, we are interested in comparing
    # their internal representation of the message data
    return self.data == other.data


class MonitorSocket(object):
  _SOCKET_TIMEOUT = 5

  def __init__(self, monitor_filename):
    """Instantiates the MonitorSocket object.

    @type monitor_filename: string
    @param monitor_filename: the filename of the UNIX raw socket on which the
                             monitor (QMP or simple one) is listening

    """
    self.monitor_filename = monitor_filename
    self.sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
    # We want to fail if the server doesn't send a complete message
    # in a reasonable amount of time
    self.sock.settimeout(self._SOCKET_TIMEOUT)
    self._connected = False

  def _check_socket(self):
    sock_stat = None
    try:
      sock_stat = os.stat(self.monitor_filename)
    except EnvironmentError, err:
      if err.errno == errno.ENOENT:
        raise errors.HypervisorError("No monitor socket found")
      else:
        raise errors.HypervisorError("Error checking monitor socket: %s",
                                     utils.ErrnoOrStr(err))
    if not stat.S_ISSOCK(sock_stat.st_mode):
      raise errors.HypervisorError("Monitor socket is not a socket")

  def _check_connection(self):
    """Make sure that the connection is established.

    """
    if not self._connected:
      raise errors.ProgrammerError("To use a MonitorSocket you need to first"
                                   " invoke connect() on it")

  def connect(self):
    """Connects to the monitor.

    Connects to the UNIX socket

    @raise errors.HypervisorError: when there are communication errors

    """
    if self._connected:
      raise errors.ProgrammerError("Cannot connect twice")

    self._check_socket()

    # Check file existance/stuff
    try:
      self.sock.connect(self.monitor_filename)
    except EnvironmentError:
      raise errors.HypervisorError("Can't connect to qmp socket")
    self._connected = True

  def close(self):
    """Closes the socket

    It cannot be used after this call.

    """
    self.sock.close()


class QmpConnection(MonitorSocket):
  """Connection to the QEMU Monitor using the QEMU Monitor Protocol (QMP).

  """
  _FIRST_MESSAGE_KEY = "QMP"
  _EVENT_KEY = "event"
  _ERROR_KEY = "error"
  _RETURN_KEY = RETURN_KEY = "return"
  _ACTUAL_KEY = ACTUAL_KEY = "actual"
  _ERROR_CLASS_KEY = "class"
  _ERROR_DESC_KEY = "desc"
  _EXECUTE_KEY = "execute"
  _ARGUMENTS_KEY = "arguments"
  _CAPABILITIES_COMMAND = "qmp_capabilities"
  _MESSAGE_END_TOKEN = "\r\n"

  def __init__(self, monitor_filename):
    super(QmpConnection, self).__init__(monitor_filename)
    self._buf = ""

  def connect(self):
    """Connects to the QMP monitor.

    Connects to the UNIX socket and makes sure that we can actually send and
    receive data to the kvm instance via QMP.

    @raise errors.HypervisorError: when there are communication errors
    @raise errors.ProgrammerError: when there are data serialization errors

    """
    super(QmpConnection, self).connect()
    # Check if we receive a correct greeting message from the server
    # (As per the QEMU Protocol Specification 0.1 - section 2.2)
    greeting = self._Recv()
    if not greeting[self._FIRST_MESSAGE_KEY]:
      self._connected = False
      raise errors.HypervisorError("kvm: QMP communication error (wrong"
                                   " server greeting")

    # This is needed because QMP can return more than one greetings
    # see https://groups.google.com/d/msg/ganeti-devel/gZYcvHKDooU/SnukC8dgS5AJ
    self._buf = ""

    # Let's put the monitor in command mode using the qmp_capabilities
    # command, or else no command will be executable.
    # (As per the QEMU Protocol Specification 0.1 - section 4)
    self.Execute(self._CAPABILITIES_COMMAND)

  def _ParseMessage(self, buf):
    """Extract and parse a QMP message from the given buffer.

    Seeks for a QMP message in the given buf. If found, it parses it and
    returns it together with the rest of the characters in the buf.
    If no message is found, returns None and the whole buffer.

    @raise errors.ProgrammerError: when there are data serialization errors

    """
    message = None
    # Check if we got the message end token (CRLF, as per the QEMU Protocol
    # Specification 0.1 - Section 2.1.1)
    pos = buf.find(self._MESSAGE_END_TOKEN)
    if pos >= 0:
      try:
        message = QmpMessage.BuildFromJsonString(buf[:pos + 1])
      except Exception, err:
        raise errors.ProgrammerError("QMP data serialization error: %s" % err)
      buf = buf[pos + 1:]

    return (message, buf)

  def _Recv(self):
    """Receives a message from QMP and decodes the received JSON object.

    @rtype: QmpMessage
    @return: the received message
    @raise errors.HypervisorError: when there are communication errors
    @raise errors.ProgrammerError: when there are data serialization errors

    """
    self._check_connection()

    # Check if there is already a message in the buffer
    (message, self._buf) = self._ParseMessage(self._buf)
    if message:
      return message

    recv_buffer = StringIO.StringIO(self._buf)
    recv_buffer.seek(len(self._buf))
    try:
      while True:
        data = self.sock.recv(4096)
        if not data:
          break
        recv_buffer.write(data)

        (message, self._buf) = self._ParseMessage(recv_buffer.getvalue())
        if message:
          return message

    except socket.timeout, err:
      raise errors.HypervisorError("Timeout while receiving a QMP message: "
                                   "%s" % (err))
    except socket.error, err:
      raise errors.HypervisorError("Unable to receive data from KVM using the"
                                   " QMP protocol: %s" % err)

  def _Send(self, message):
    """Encodes and sends a message to KVM using QMP.

    @type message: QmpMessage
    @param message: message to send to KVM
    @raise errors.HypervisorError: when there are communication errors
    @raise errors.ProgrammerError: when there are data serialization errors

    """
    self._check_connection()
    try:
      message_str = str(message)
    except Exception, err:
      raise errors.ProgrammerError("QMP data deserialization error: %s" % err)

    try:
      self.sock.sendall(message_str)
    except socket.timeout, err:
      raise errors.HypervisorError("Timeout while sending a QMP message: "
                                   "%s (%s)" % (err.string, err.errno))
    except socket.error, err:
      raise errors.HypervisorError("Unable to send data from KVM using the"
                                   " QMP protocol: %s" % err)

  def Execute(self, command, arguments=None):
    """Executes a QMP command and returns the response of the server.

    @type command: str
    @param command: the command to execute
    @type arguments: dict
    @param arguments: dictionary of arguments to be passed to the command
    @rtype: dict
    @return: dictionary representing the received JSON object
    @raise errors.HypervisorError: when there are communication errors
    @raise errors.ProgrammerError: when there are data serialization errors

    """
    self._check_connection()
    message = QmpMessage({self._EXECUTE_KEY: command})
    if arguments:
      message[self._ARGUMENTS_KEY] = arguments
    self._Send(message)

    # Events can occur between the sending of the command and the reception
    # of the response, so we need to filter out messages with the event key.
    while True:
      response = self._Recv()
      err = response[self._ERROR_KEY]
      if err:
        raise errors.HypervisorError("kvm: error executing the %s"
                                     " command: %s (%s):" %
                                     (command,
                                      err[self._ERROR_DESC_KEY],
                                      err[self._ERROR_CLASS_KEY]))

      elif not response[self._EVENT_KEY]:
        return response


class KVMHypervisor(hv_base.BaseHypervisor):
  """KVM hypervisor interface

  """
  CAN_MIGRATE = True

  _ROOT_DIR = pathutils.RUN_DIR + "/kvm-hypervisor"
  _PIDS_DIR = _ROOT_DIR + "/pid" # contains live instances pids
  _UIDS_DIR = _ROOT_DIR + "/uid" # contains instances reserved uids
  _CTRL_DIR = _ROOT_DIR + "/ctrl" # contains instances control sockets
  _CONF_DIR = _ROOT_DIR + "/conf" # contains instances startup data
  _NICS_DIR = _ROOT_DIR + "/nic" # contains instances nic <-> tap associations
  _KEYMAP_DIR = _ROOT_DIR + "/keymap" # contains instances keymaps
  # KVM instances with chroot enabled are started in empty chroot directories.
  _CHROOT_DIR = _ROOT_DIR + "/chroot" # for empty chroot directories
  # After an instance is stopped, its chroot directory is removed.
  # If the chroot directory is not empty, it can't be removed.
  # A non-empty chroot directory indicates a possible security incident.
  # To support forensics, the non-empty chroot directory is quarantined in
  # a separate directory, called 'chroot-quarantine'.
  _CHROOT_QUARANTINE_DIR = _ROOT_DIR + "/chroot-quarantine"
  _DIRS = [_ROOT_DIR, _PIDS_DIR, _UIDS_DIR, _CTRL_DIR, _CONF_DIR, _NICS_DIR,
           _CHROOT_DIR, _CHROOT_QUARANTINE_DIR, _KEYMAP_DIR]

  PARAMETERS = {
    constants.HV_KVM_PATH: hv_base.REQ_FILE_CHECK,
    constants.HV_KERNEL_PATH: hv_base.OPT_FILE_CHECK,
    constants.HV_INITRD_PATH: hv_base.OPT_FILE_CHECK,
    constants.HV_ROOT_PATH: hv_base.NO_CHECK,
    constants.HV_KERNEL_ARGS: hv_base.NO_CHECK,
    constants.HV_ACPI: hv_base.NO_CHECK,
    constants.HV_SERIAL_CONSOLE: hv_base.NO_CHECK,
    constants.HV_SERIAL_SPEED: hv_base.NO_CHECK,
    constants.HV_VNC_BIND_ADDRESS:
      (False, lambda x: (netutils.IP4Address.IsValid(x) or
                         utils.IsNormAbsPath(x)),
       "The VNC bind address must be either a valid IP address or an absolute"
       " pathname", None, None),
    constants.HV_VNC_TLS: hv_base.NO_CHECK,
    constants.HV_VNC_X509: hv_base.OPT_DIR_CHECK,
    constants.HV_VNC_X509_VERIFY: hv_base.NO_CHECK,
    constants.HV_VNC_PASSWORD_FILE: hv_base.OPT_FILE_CHECK,
    constants.HV_KVM_SPICE_BIND: hv_base.NO_CHECK, # will be checked later
    constants.HV_KVM_SPICE_IP_VERSION:
      (False, lambda x: (x == constants.IFACE_NO_IP_VERSION_SPECIFIED or
                         x in constants.VALID_IP_VERSIONS),
       "The SPICE IP version should be 4 or 6",
       None, None),
    constants.HV_KVM_SPICE_PASSWORD_FILE: hv_base.OPT_FILE_CHECK,
    constants.HV_KVM_SPICE_LOSSLESS_IMG_COMPR:
      hv_base.ParamInSet(
        False, constants.HT_KVM_SPICE_VALID_LOSSLESS_IMG_COMPR_OPTIONS),
    constants.HV_KVM_SPICE_JPEG_IMG_COMPR:
      hv_base.ParamInSet(
        False, constants.HT_KVM_SPICE_VALID_LOSSY_IMG_COMPR_OPTIONS),
    constants.HV_KVM_SPICE_ZLIB_GLZ_IMG_COMPR:
      hv_base.ParamInSet(
        False, constants.HT_KVM_SPICE_VALID_LOSSY_IMG_COMPR_OPTIONS),
    constants.HV_KVM_SPICE_STREAMING_VIDEO_DETECTION:
      hv_base.ParamInSet(
        False, constants.HT_KVM_SPICE_VALID_VIDEO_STREAM_DETECTION_OPTIONS),
    constants.HV_KVM_SPICE_AUDIO_COMPR: hv_base.NO_CHECK,
    constants.HV_KVM_SPICE_USE_TLS: hv_base.NO_CHECK,
    constants.HV_KVM_SPICE_TLS_CIPHERS: hv_base.NO_CHECK,
    constants.HV_KVM_SPICE_USE_VDAGENT: hv_base.NO_CHECK,
    constants.HV_KVM_FLOPPY_IMAGE_PATH: hv_base.OPT_FILE_CHECK,
    constants.HV_CDROM_IMAGE_PATH: hv_base.OPT_FILE_CHECK,
    constants.HV_KVM_CDROM2_IMAGE_PATH: hv_base.OPT_FILE_CHECK,
    constants.HV_BOOT_ORDER:
      hv_base.ParamInSet(True, constants.HT_KVM_VALID_BO_TYPES),
    constants.HV_NIC_TYPE:
      hv_base.ParamInSet(True, constants.HT_KVM_VALID_NIC_TYPES),
    constants.HV_DISK_TYPE:
      hv_base.ParamInSet(True, constants.HT_KVM_VALID_DISK_TYPES),
    constants.HV_KVM_CDROM_DISK_TYPE:
      hv_base.ParamInSet(False, constants.HT_KVM_VALID_DISK_TYPES),
    constants.HV_USB_MOUSE:
      hv_base.ParamInSet(False, constants.HT_KVM_VALID_MOUSE_TYPES),
    constants.HV_KEYMAP: hv_base.NO_CHECK,
    constants.HV_MIGRATION_PORT: hv_base.REQ_NET_PORT_CHECK,
    constants.HV_MIGRATION_BANDWIDTH: hv_base.REQ_NONNEGATIVE_INT_CHECK,
    constants.HV_MIGRATION_DOWNTIME: hv_base.REQ_NONNEGATIVE_INT_CHECK,
    constants.HV_MIGRATION_MODE: hv_base.MIGRATION_MODE_CHECK,
    constants.HV_USE_LOCALTIME: hv_base.NO_CHECK,
    constants.HV_DISK_CACHE:
      hv_base.ParamInSet(True, constants.HT_VALID_CACHE_TYPES),
    constants.HV_SECURITY_MODEL:
      hv_base.ParamInSet(True, constants.HT_KVM_VALID_SM_TYPES),
    constants.HV_SECURITY_DOMAIN: hv_base.NO_CHECK,
    constants.HV_KVM_FLAG:
      hv_base.ParamInSet(False, constants.HT_KVM_FLAG_VALUES),
    constants.HV_VHOST_NET: hv_base.NO_CHECK,
    constants.HV_KVM_USE_CHROOT: hv_base.NO_CHECK,
    constants.HV_MEM_PATH: hv_base.OPT_DIR_CHECK,
    constants.HV_REBOOT_BEHAVIOR:
      hv_base.ParamInSet(True, constants.REBOOT_BEHAVIORS),
    constants.HV_CPU_MASK: hv_base.OPT_MULTI_CPU_MASK_CHECK,
    constants.HV_CPU_TYPE: hv_base.NO_CHECK,
    constants.HV_CPU_CORES: hv_base.OPT_NONNEGATIVE_INT_CHECK,
    constants.HV_CPU_THREADS: hv_base.OPT_NONNEGATIVE_INT_CHECK,
    constants.HV_CPU_SOCKETS: hv_base.OPT_NONNEGATIVE_INT_CHECK,
    constants.HV_SOUNDHW: hv_base.NO_CHECK,
    constants.HV_USB_DEVICES: hv_base.NO_CHECK,
    constants.HV_VGA: hv_base.NO_CHECK,
    constants.HV_KVM_EXTRA: hv_base.NO_CHECK,
    constants.HV_KVM_MACHINE_VERSION: hv_base.NO_CHECK,
    constants.HV_VNET_HDR: hv_base.NO_CHECK,
    }

  _VIRTIO = "virtio"
  _VIRTIO_NET_PCI = "virtio-net-pci"
  _VIRTIO_BLK_PCI = "virtio-blk-pci"

  _MIGRATION_STATUS_RE = re.compile("Migration\s+status:\s+(\w+)",
                                    re.M | re.I)
  _MIGRATION_PROGRESS_RE = \
    re.compile(r"\s*transferred\s+ram:\s+(?P<transferred>\d+)\s+kbytes\s*\n"
               r"\s*remaining\s+ram:\s+(?P<remaining>\d+)\s+kbytes\s*\n"
               r"\s*total\s+ram:\s+(?P<total>\d+)\s+kbytes\s*\n", re.I)

  _MIGRATION_INFO_MAX_BAD_ANSWERS = 5
  _MIGRATION_INFO_RETRY_DELAY = 2

  _VERSION_RE = re.compile(r"\b(\d+)\.(\d+)(\.(\d+))?\b")

  _CPU_INFO_RE = re.compile(r"cpu\s+\#(\d+).*thread_id\s*=\s*(\d+)", re.I)
  _CPU_INFO_CMD = "info cpus"
  _CONT_CMD = "cont"

  _DEFAULT_MACHINE_VERSION_RE = re.compile(r"^(\S+).*\(default\)", re.M)
  _CHECK_MACHINE_VERSION_RE = \
    staticmethod(lambda x: re.compile(r"^(%s)[ ]+.*PC" % x, re.M))

  _QMP_RE = re.compile(r"^-qmp\s", re.M)
  _SPICE_RE = re.compile(r"^-spice\s", re.M)
  _VHOST_RE = re.compile(r"^-net\s.*,vhost=on|off", re.M)
  _ENABLE_KVM_RE = re.compile(r"^-enable-kvm\s", re.M)
  _DISABLE_KVM_RE = re.compile(r"^-disable-kvm\s", re.M)
  _NETDEV_RE = re.compile(r"^-netdev\s", re.M)
  _DISPLAY_RE = re.compile(r"^-display\s", re.M)
  _MACHINE_RE = re.compile(r"^-machine\s", re.M)
  _VIRTIO_NET_RE = re.compile(r"^name \"%s\"" % _VIRTIO_NET_PCI, re.M)
  _VIRTIO_BLK_RE = re.compile(r"^name \"%s\"" % _VIRTIO_BLK_PCI, re.M)
  # match  -drive.*boot=on|off on different lines, but in between accept only
  # dashes not preceeded by a new line (which would mean another option
  # different than -drive is starting)
  _BOOT_RE = re.compile(r"^-drive\s([^-]|(?<!^)-)*,boot=on\|off", re.M | re.S)

  _INFO_PCI_RE = re.compile(r'Bus.*device[ ]*(\d+).*')
  _INFO_PCI_CMD = "info pci"
  _FIND_PCI_DEVICE_RE = \
    staticmethod(lambda pci, devid:
      re.compile(r'Bus.*device[ ]*%d,(.*\n){5,6}.*id "%s"' % (pci, devid),
                 re.M))

  _INFO_VERSION_RE = \
    re.compile(r'^QEMU (\d+)\.(\d+)(\.(\d+))?.*monitor.*', re.M)
  _INFO_VERSION_CMD = "info version"

  _DEFAULT_PCI_RESERVATIONS = "11110000000000000000000000000000"

  ANCILLARY_FILES = [
    _KVM_NETWORK_SCRIPT,
    ]
  ANCILLARY_FILES_OPT = [
    _KVM_NETWORK_SCRIPT,
    ]

  # Supported kvm options to get output from
  _KVMOPT_HELP = "help"
  _KVMOPT_MLIST = "mlist"
  _KVMOPT_DEVICELIST = "devicelist"

  # Command to execute to get the output from kvm, and whether to
  # accept the output even on failure.
  _KVMOPTS_CMDS = {
    _KVMOPT_HELP: (["--help"], False),
    _KVMOPT_MLIST: (["-M", "?"], False),
    _KVMOPT_DEVICELIST: (["-device", "?"], True),
  }

  def __init__(self):
    hv_base.BaseHypervisor.__init__(self)
    # Let's make sure the directories we need exist, even if the RUN_DIR lives
    # in a tmpfs filesystem or has been otherwise wiped out.
    dirs = [(dname, constants.RUN_DIRS_MODE) for dname in self._DIRS]
    utils.EnsureDirs(dirs)

  @classmethod
  def _InstancePidFile(cls, instance_name):
    """Returns the instance pidfile.

    """
    return utils.PathJoin(cls._PIDS_DIR, instance_name)

  @classmethod
  def _InstanceUidFile(cls, instance_name):
    """Returns the instance uidfile.

    """
    return utils.PathJoin(cls._UIDS_DIR, instance_name)

  @classmethod
  def _InstancePidInfo(cls, pid):
    """Check pid file for instance information.

    Check that a pid file is associated with an instance, and retrieve
    information from its command line.

    @type pid: string or int
    @param pid: process id of the instance to check
    @rtype: tuple
    @return: (instance_name, memory, vcpus)
    @raise errors.HypervisorError: when an instance cannot be found

    """
    alive = utils.IsProcessAlive(pid)
    if not alive:
      raise errors.HypervisorError("Cannot get info for pid %s" % pid)

    cmdline_file = utils.PathJoin("/proc", str(pid), "cmdline")
    try:
      cmdline = utils.ReadFile(cmdline_file)
    except EnvironmentError, err:
      raise errors.HypervisorError("Can't open cmdline file for pid %s: %s" %
                                   (pid, err))

    instance = None
    memory = 0
    vcpus = 0

    arg_list = cmdline.split("\x00")
    while arg_list:
      arg = arg_list.pop(0)
      if arg == "-name":
        instance = arg_list.pop(0)
      elif arg == "-m":
        memory = int(arg_list.pop(0))
      elif arg == "-smp":
        vcpus = int(arg_list.pop(0).split(",")[0])

    if instance is None:
      raise errors.HypervisorError("Pid %s doesn't contain a ganeti kvm"
                                   " instance" % pid)

    return (instance, memory, vcpus)

  def _InstancePidAlive(self, instance_name):
    """Returns the instance pidfile, pid, and liveness.

    @type instance_name: string
    @param instance_name: instance name
    @rtype: tuple
    @return: (pid file name, pid, liveness)

    """
    pidfile = self._InstancePidFile(instance_name)
    pid = utils.ReadPidFile(pidfile)

    alive = False
    try:
      cmd_instance = self._InstancePidInfo(pid)[0]
      alive = (cmd_instance == instance_name)
    except errors.HypervisorError:
      pass

    return (pidfile, pid, alive)

  def _CheckDown(self, instance_name):
    """Raises an error unless the given instance is down.

    """
    alive = self._InstancePidAlive(instance_name)[2]
    if alive:
      raise errors.HypervisorError("Failed to start instance %s: %s" %
                                   (instance_name, "already running"))

  @classmethod
  def _InstanceMonitor(cls, instance_name):
    """Returns the instance monitor socket name

    """
    return utils.PathJoin(cls._CTRL_DIR, "%s.monitor" % instance_name)

  @classmethod
  def _InstanceSerial(cls, instance_name):
    """Returns the instance serial socket name

    """
    return utils.PathJoin(cls._CTRL_DIR, "%s.serial" % instance_name)

  @classmethod
  def _InstanceQmpMonitor(cls, instance_name):
    """Returns the instance serial QMP socket name

    """
    return utils.PathJoin(cls._CTRL_DIR, "%s.qmp" % instance_name)

  @staticmethod
  def _SocatUnixConsoleParams():
    """Returns the correct parameters for socat

    If we have a new-enough socat we can use raw mode with an escape character.

    """
    if constants.SOCAT_USE_ESCAPE:
      return "raw,echo=0,escape=%s" % constants.SOCAT_ESCAPE_CODE
    else:
      return "echo=0,icanon=0"

  @classmethod
  def _InstanceKVMRuntime(cls, instance_name):
    """Returns the instance KVM runtime filename

    """
    return utils.PathJoin(cls._CONF_DIR, "%s.runtime" % instance_name)

  @classmethod
  def _InstanceChrootDir(cls, instance_name):
    """Returns the name of the KVM chroot dir of the instance

    """
    return utils.PathJoin(cls._CHROOT_DIR, instance_name)

  @classmethod
  def _InstanceNICDir(cls, instance_name):
    """Returns the name of the directory holding the tap device files for a
    given instance.

    """
    return utils.PathJoin(cls._NICS_DIR, instance_name)

  @classmethod
  def _InstanceNICFile(cls, instance_name, seq_or_uuid):
    """Returns the name of the file containing the tap device for a given NIC

    """
    return utils.PathJoin(cls._InstanceNICDir(instance_name), str(seq_or_uuid))

  @classmethod
  def _GetInstanceNICTap(cls, instance_name, nic):
    """Returns the tap for the corresponding nic

    Search for tap file named after NIC's uuid.
    For old instances without uuid indexed tap files returns nothing.

    """
    try:
      return utils.ReadFile(cls._InstanceNICFile(instance_name, nic.uuid))
    except EnvironmentError:
      pass

  @classmethod
  def _WriteInstanceNICFiles(cls, instance_name, seq, nic, tap):
    """Write tap name to both instance NIC files

    """
    for ident in [seq, nic.uuid]:
      utils.WriteFile(cls._InstanceNICFile(instance_name, ident), data=tap)

  @classmethod
  def _RemoveInstanceNICFiles(cls, instance_name, seq, nic):
    """Write tap name to both instance NIC files

    """
    for ident in [seq, nic.uuid]:
      utils.RemoveFile(cls._InstanceNICFile(instance_name, ident))

  @classmethod
  def _InstanceKeymapFile(cls, instance_name):
    """Returns the name of the file containing the keymap for a given instance

    """
    return utils.PathJoin(cls._KEYMAP_DIR, instance_name)

  @classmethod
  def _TryReadUidFile(cls, uid_file):
    """Try to read a uid file

    """
    if os.path.exists(uid_file):
      try:
        uid = int(utils.ReadOneLineFile(uid_file))
        return uid
      except EnvironmentError:
        logging.warning("Can't read uid file", exc_info=True)
      except (TypeError, ValueError):
        logging.warning("Can't parse uid file contents", exc_info=True)
    return None

  @classmethod
  def _RemoveInstanceRuntimeFiles(cls, pidfile, instance_name):
    """Removes an instance's rutime sockets/files/dirs.

    """
    # This takes info from NICDir and RuntimeFile
    cls._UnconfigureInstanceNICs(instance_name)
    utils.RemoveFile(pidfile)
    utils.RemoveFile(cls._InstanceMonitor(instance_name))
    utils.RemoveFile(cls._InstanceSerial(instance_name))
    utils.RemoveFile(cls._InstanceQmpMonitor(instance_name))
    utils.RemoveFile(cls._InstanceKVMRuntime(instance_name))
    utils.RemoveFile(cls._InstanceKeymapFile(instance_name))
    uid_file = cls._InstanceUidFile(instance_name)
    uid = cls._TryReadUidFile(uid_file)
    utils.RemoveFile(uid_file)
    if uid is not None:
      uidpool.ReleaseUid(uid)
    try:
      shutil.rmtree(cls._InstanceNICDir(instance_name))
    except OSError, err:
      if err.errno != errno.ENOENT:
        raise
    try:
      chroot_dir = cls._InstanceChrootDir(instance_name)
      utils.RemoveDir(chroot_dir)
    except OSError, err:
      if err.errno == errno.ENOTEMPTY:
        # The chroot directory is expected to be empty, but it isn't.
        new_chroot_dir = tempfile.mkdtemp(dir=cls._CHROOT_QUARANTINE_DIR,
                                          prefix="%s-%s-" %
                                          (instance_name,
                                           utils.TimestampForFilename()))
        logging.warning("The chroot directory of instance %s can not be"
                        " removed as it is not empty. Moving it to the"
                        " quarantine instead. Please investigate the"
                        " contents (%s) and clean up manually",
                        instance_name, new_chroot_dir)
        utils.RenameFile(chroot_dir, new_chroot_dir)
      else:
        raise

  @staticmethod
  def _CreateNICEnv(instance_name, nic, tap, seq=None, instance_tags=None):
    """Create environment variables for a specific NIC

    This is needed during NIC ifup/ifdown scripts.
    Since instance tags may change during NIC creation and removal
    and because during cleanup instance object is not available we
    pass them only upon NIC creation (instance startup/NIC hot-plugging).

    """
    env = {
      "PATH": "%s:/sbin:/usr/sbin" % os.environ["PATH"],
      "INSTANCE": instance_name,
      "MAC": nic.mac,
      "MODE": nic.nicparams[constants.NIC_MODE],
      "INTERFACE_UUID": nic.uuid,
    }

    if instance_tags:
      env["TAGS"] = " ".join(instance_tags)

    # This should always be available except for old instances in the
    # cluster without uuid indexed tap files.
    if tap:
      env["INTERFACE"] = tap

    if seq:
      env["INTERFACE_INDEX"] = str(seq)

    if nic.ip:
      env["IP"] = nic.ip

    if nic.name:
      env["INTERFACE_NAME"] = nic.name

    if nic.nicparams[constants.NIC_LINK]:
      env["LINK"] = nic.nicparams[constants.NIC_LINK]

    if nic.network:
      n = objects.Network.FromDict(nic.netinfo)
      env.update(n.HooksDict())

    if nic.nicparams[constants.NIC_MODE] == constants.NIC_MODE_BRIDGED:
      env["BRIDGE"] = nic.nicparams[constants.NIC_LINK]

    return env

  @classmethod
  def _ConfigureNIC(cls, instance, seq, nic, tap):
    """Run the network configuration script for a specified NIC

    @param instance: instance we're acting on
    @type instance: instance object
    @param seq: nic sequence number
    @type seq: int
    @param nic: nic we're acting on
    @type nic: nic object
    @param tap: the host's tap interface this NIC corresponds to
    @type tap: str

    """
    env = cls._CreateNICEnv(instance.name, nic, tap, seq, instance.GetTags())
    result = utils.RunCmd([pathutils.KVM_IFUP, tap], env=env)
    if result.failed:
      raise errors.HypervisorError("Failed to configure interface %s: %s;"
                                   " network configuration script output: %s" %
                                   (tap, result.fail_reason, result.output))

  @classmethod
  def _UnconfigureNic(cls, instance_name, nic, only_local=True):
    """Run ifdown script for a specific NIC

    This is executed during instance cleanup and NIC hot-unplug

    @param instance: instance we're acting on
    @type instance: instance object
    @param nic: nic we're acting on
    @type nic: nic object
    @param localy: whether ifdown script should reset global conf (dns) or not
    @type localy: boolean

    """
    tap = cls._GetInstanceNICTap(instance_name, nic)
    env = cls._CreateNICEnv(instance_name, nic, tap)
    arg2 = str(only_local).lower()
    result = utils.RunCmd([pathutils.KVM_IFDOWN, tap, arg2], env=env)
    if result.failed:
      raise errors.HypervisorError("Failed to unconfigure interface %s: %s;"
                                   " network configuration script output: %s" %
                                   (tap, result.fail_reason, result.output))

  @staticmethod
  def _VerifyAffinityPackage():
    if affinity is None:
      raise errors.HypervisorError("affinity Python package not"
                                   " found; cannot use CPU pinning under KVM")

  @staticmethod
  def _BuildAffinityCpuMask(cpu_list):
    """Create a CPU mask suitable for sched_setaffinity from a list of
    CPUs.

    See man taskset for more info on sched_setaffinity masks.
    For example: [ 0, 2, 5, 6 ] will return 101 (0x65, 0..01100101).

    @type cpu_list: list of int
    @param cpu_list: list of physical CPU numbers to map to vCPUs in order
    @rtype: int
    @return: a bit mask of CPU affinities

    """
    if cpu_list == constants.CPU_PINNING_OFF:
      return constants.CPU_PINNING_ALL_KVM
    else:
      return sum(2 ** cpu for cpu in cpu_list)

  @classmethod
  def _AssignCpuAffinity(cls, cpu_mask, process_id, thread_dict):
    """Change CPU affinity for running VM according to given CPU mask.

    @param cpu_mask: CPU mask as given by the user. e.g. "0-2,4:all:1,3"
    @type cpu_mask: string
    @param process_id: process ID of KVM process. Used to pin entire VM
                       to physical CPUs.
    @type process_id: int
    @param thread_dict: map of virtual CPUs to KVM thread IDs
    @type thread_dict: dict int:int

    """
    # Convert the string CPU mask to a list of list of int's
    cpu_list = utils.ParseMultiCpuMask(cpu_mask)

    if len(cpu_list) == 1:
      all_cpu_mapping = cpu_list[0]
      if all_cpu_mapping == constants.CPU_PINNING_OFF:
        # If CPU pinning has 1 entry that's "all", then do nothing
        pass
      else:
        # If CPU pinning has one non-all entry, map the entire VM to
        # one set of physical CPUs
        cls._VerifyAffinityPackage()
        affinity.set_process_affinity_mask(
          process_id, cls._BuildAffinityCpuMask(all_cpu_mapping))
    else:
      # The number of vCPUs mapped should match the number of vCPUs
      # reported by KVM. This was already verified earlier, so
      # here only as a sanity check.
      assert len(thread_dict) == len(cpu_list)
      cls._VerifyAffinityPackage()

      # For each vCPU, map it to the proper list of physical CPUs
      for vcpu, i in zip(cpu_list, range(len(cpu_list))):
        affinity.set_process_affinity_mask(thread_dict[i],
                                           cls._BuildAffinityCpuMask(vcpu))

  def _GetVcpuThreadIds(self, instance_name):
    """Get a mapping of vCPU no. to thread IDs for the instance

    @type instance_name: string
    @param instance_name: instance in question
    @rtype: dictionary of int:int
    @return: a dictionary mapping vCPU numbers to thread IDs

    """
    result = {}
    output = self._CallMonitorCommand(instance_name, self._CPU_INFO_CMD)
    for line in output.stdout.splitlines():
      match = self._CPU_INFO_RE.search(line)
      if not match:
        continue
      grp = map(int, match.groups())
      result[grp[0]] = grp[1]

    return result

  def _ExecuteCpuAffinity(self, instance_name, cpu_mask):
    """Complete CPU pinning.

    @type instance_name: string
    @param instance_name: name of instance
    @type cpu_mask: string
    @param cpu_mask: CPU pinning mask as entered by user

    """
    # Get KVM process ID, to be used if need to pin entire VM
    _, pid, _ = self._InstancePidAlive(instance_name)
    # Get vCPU thread IDs, to be used if need to pin vCPUs separately
    thread_dict = self._GetVcpuThreadIds(instance_name)
    # Run CPU pinning, based on configured mask
    self._AssignCpuAffinity(cpu_mask, pid, thread_dict)

  def ListInstances(self):
    """Get the list of running instances.

    We can do this by listing our live instances directory and
    checking whether the associated kvm process is still alive.

    """
    result = []
    for name in os.listdir(self._PIDS_DIR):
      if self._InstancePidAlive(name)[2]:
        result.append(name)
    return result

  def GetInstanceInfo(self, instance_name):
    """Get instance properties.

    @type instance_name: string
    @param instance_name: the instance name
    @rtype: tuple of strings
    @return: (name, id, memory, vcpus, stat, times)

    """
    _, pid, alive = self._InstancePidAlive(instance_name)
    if not alive:
      return None

    _, memory, vcpus = self._InstancePidInfo(pid)
    istat = "---b-"
    times = "0"

    try:
      qmp = QmpConnection(self._InstanceQmpMonitor(instance_name))
      qmp.connect()
      vcpus = len(qmp.Execute("query-cpus")[qmp.RETURN_KEY])
      # Will fail if ballooning is not enabled, but we can then just resort to
      # the value above.
      mem_bytes = qmp.Execute("query-balloon")[qmp.RETURN_KEY][qmp.ACTUAL_KEY]
      memory = mem_bytes / 1048576
    except errors.HypervisorError:
      pass

    return (instance_name, pid, memory, vcpus, istat, times)

  def GetAllInstancesInfo(self):
    """Get properties of all instances.

    @return: list of tuples (name, id, memory, vcpus, stat, times)

    """
    data = []
    for name in os.listdir(self._PIDS_DIR):
      try:
        info = self.GetInstanceInfo(name)
      except errors.HypervisorError:
        # Ignore exceptions due to instances being shut down
        continue
      if info:
        data.append(info)
    return data

  def _GenerateKVMBlockDevicesOptions(self, instance, kvm_disks,
                                      kvmhelp, devlist):
    """Generate KVM options regarding instance's block devices.

    @type instance: L{objects.Instance}
    @param instance: the instance object
    @type kvm_disks: list of tuples
    @param kvm_disks: list of tuples [(disk, link_name)..]
    @type kvmhelp: string
    @param kvmhelp: output of kvm --help
    @type devlist: string
    @param devlist: output of kvm -device ?
    @rtype: list
    @return: list of command line options eventually used by kvm executable

    """
    hvp = instance.hvparams
    kernel_path = hvp[constants.HV_KERNEL_PATH]
    if kernel_path:
      boot_disk = False
    else:
      boot_disk = hvp[constants.HV_BOOT_ORDER] == constants.HT_BO_DISK

    # whether this is an older KVM version that uses the boot=on flag
    # on devices
    needs_boot_flag = self._BOOT_RE.search(kvmhelp)

    dev_opts = []
    device_driver = None
    disk_type = hvp[constants.HV_DISK_TYPE]
    if disk_type == constants.HT_DISK_PARAVIRTUAL:
      if_val = ",if=%s" % self._VIRTIO
      try:
        if self._VIRTIO_BLK_RE.search(devlist):
          if_val = ",if=none"
          # will be passed in -device option as driver
          device_driver = self._VIRTIO_BLK_PCI
      except errors.HypervisorError, _:
        pass
    else:
      if_val = ",if=%s" % disk_type
    # Cache mode
    disk_cache = hvp[constants.HV_DISK_CACHE]
    if instance.disk_template in constants.DTS_EXT_MIRROR:
      if disk_cache != "none":
        # TODO: make this a hard error, instead of a silent overwrite
        logging.warning("KVM: overriding disk_cache setting '%s' with 'none'"
                        " to prevent shared storage corruption on migration",
                        disk_cache)
      cache_val = ",cache=none"
    elif disk_cache != constants.HT_CACHE_DEFAULT:
      cache_val = ",cache=%s" % disk_cache
    else:
      cache_val = ""
    for idx, (cfdev, link_name) in enumerate(kvm_disks):
      if cfdev.mode != constants.DISK_RDWR:
        raise errors.HypervisorError("Instance has read-only disks which"
                                     " are not supported by KVM")
      # TODO: handle FD_LOOP and FD_BLKTAP (?)
      boot_val = ""
      if boot_disk:
        dev_opts.extend(["-boot", "c"])
        boot_disk = False
        if needs_boot_flag and disk_type != constants.HT_DISK_IDE:
          boot_val = ",boot=on"

      # For ext we allow overriding disk_cache hypervisor params per disk
      disk_cache = cfdev.params.get("cache", None)
      if disk_cache:
        cache_val = ",cache=%s" % disk_cache
      drive_val = "file=%s,format=raw%s%s%s" % \
                  (link_name, if_val, boot_val, cache_val)

      if device_driver:
        # kvm_disks are the 4th entry of runtime file that did not exist in
        # the past. That means that cfdev should always have pci slot and
        # _GenerateDeviceKVMId() will not raise a exception.
        kvm_devid = _GenerateDeviceKVMId(constants.HOTPLUG_TARGET_DISK,
                                         cfdev, idx)
        drive_val += (",id=%s" % kvm_devid)
        if cfdev.pci:
          drive_val += (",bus=0,unit=%d" % cfdev.pci)
        dev_val = ("%s,drive=%s,id=%s" %
                   (device_driver, kvm_devid, kvm_devid))
        if cfdev.pci:
          dev_val += ",bus=pci.0,addr=%s" % hex(cfdev.pci)
        dev_opts.extend(["-device", dev_val])

      # TODO: export disk geometry in IDISK_PARAMS
      heads = cfdev.params.get('heads', None)
      secs = cfdev.params.get('secs', None)
      if heads and secs:
        nr_sectors = cfdev.size * 1024 * 1024 / 512
        cyls = nr_sectors / (int(heads) * int(secs))
        if cyls > 16383:
          cyls = 16383
        elif cyls < 2:
          cyls = 2
        if cyls and heads and secs:
          drive_val += (",cyls=%d,heads=%d,secs=%d" %
                        (cyls, int(heads), int(secs)))

      dev_opts.extend(["-drive", drive_val])

    return dev_opts

  def _GenerateKVMRuntime(self, instance, block_devices, startup_paused,
                          kvmhelp):
    """Generate KVM information to start an instance.

    @type kvmhelp: string
    @param kvmhelp: output of kvm --help
    @attention: this function must not have any side-effects; for
        example, it must not write to the filesystem, or read values
        from the current system the are expected to differ between
        nodes, since it is only run once at instance startup;
        actions/kvm arguments that can vary between systems should be
        done in L{_ExecuteKVMRuntime}

    """
    # pylint: disable=R0912,R0914,R0915
    hvp = instance.hvparams
    self.ValidateParameters(hvp)

    pidfile = self._InstancePidFile(instance.name)
    kvm = hvp[constants.HV_KVM_PATH]
    kvm_cmd = [kvm]
    # used just by the vnc server, if enabled
    kvm_cmd.extend(["-name", instance.name])
    kvm_cmd.extend(["-m", instance.beparams[constants.BE_MAXMEM]])

    smp_list = ["%s" % instance.beparams[constants.BE_VCPUS]]
    if hvp[constants.HV_CPU_CORES]:
      smp_list.append("cores=%s" % hvp[constants.HV_CPU_CORES])
    if hvp[constants.HV_CPU_THREADS]:
      smp_list.append("threads=%s" % hvp[constants.HV_CPU_THREADS])
    if hvp[constants.HV_CPU_SOCKETS]:
      smp_list.append("sockets=%s" % hvp[constants.HV_CPU_SOCKETS])

    kvm_cmd.extend(["-smp", ",".join(smp_list)])

    kvm_cmd.extend(["-pidfile", pidfile])
    kvm_cmd.extend(["-balloon", "virtio"])
    kvm_cmd.extend(["-daemonize"])
    if not instance.hvparams[constants.HV_ACPI]:
      kvm_cmd.extend(["-no-acpi"])
    if instance.hvparams[constants.HV_REBOOT_BEHAVIOR] == \
        constants.INSTANCE_REBOOT_EXIT:
      kvm_cmd.extend(["-no-reboot"])

    mversion = hvp[constants.HV_KVM_MACHINE_VERSION]
    if not mversion:
      mversion = self._GetDefaultMachineVersion(kvm)
    if self._MACHINE_RE.search(kvmhelp):
      # TODO (2.8): kernel_irqchip and kvm_shadow_mem machine properties, as
      # extra hypervisor parameters. We should also investigate whether and how
      # shadow_mem should be considered for the resource model.
      if (hvp[constants.HV_KVM_FLAG] == constants.HT_KVM_ENABLED):
        specprop = ",accel=kvm"
      else:
        specprop = ""
      machinespec = "%s%s" % (mversion, specprop)
      kvm_cmd.extend(["-machine", machinespec])
    else:
      kvm_cmd.extend(["-M", mversion])
      if (hvp[constants.HV_KVM_FLAG] == constants.HT_KVM_ENABLED and
          self._ENABLE_KVM_RE.search(kvmhelp)):
        kvm_cmd.extend(["-enable-kvm"])
      elif (hvp[constants.HV_KVM_FLAG] == constants.HT_KVM_DISABLED and
            self._DISABLE_KVM_RE.search(kvmhelp)):
        kvm_cmd.extend(["-disable-kvm"])

    kernel_path = hvp[constants.HV_KERNEL_PATH]
    if kernel_path:
      boot_cdrom = boot_floppy = boot_network = False
    else:
      boot_cdrom = hvp[constants.HV_BOOT_ORDER] == constants.HT_BO_CDROM
      boot_floppy = hvp[constants.HV_BOOT_ORDER] == constants.HT_BO_FLOPPY
      boot_network = hvp[constants.HV_BOOT_ORDER] == constants.HT_BO_NETWORK

    if startup_paused:
      kvm_cmd.extend([_KVM_START_PAUSED_FLAG])

    if boot_network:
      kvm_cmd.extend(["-boot", "n"])

    # whether this is an older KVM version that uses the boot=on flag
    # on devices
    needs_boot_flag = self._BOOT_RE.search(kvmhelp)

    disk_type = hvp[constants.HV_DISK_TYPE]

    #Now we can specify a different device type for CDROM devices.
    cdrom_disk_type = hvp[constants.HV_KVM_CDROM_DISK_TYPE]
    if not cdrom_disk_type:
      cdrom_disk_type = disk_type

    iso_image = hvp[constants.HV_CDROM_IMAGE_PATH]
    if iso_image:
      options = ",format=raw,media=cdrom"
      # set cdrom 'if' type
      if boot_cdrom:
        actual_cdrom_type = constants.HT_DISK_IDE
      elif cdrom_disk_type == constants.HT_DISK_PARAVIRTUAL:
        actual_cdrom_type = "virtio"
      else:
        actual_cdrom_type = cdrom_disk_type
      if_val = ",if=%s" % actual_cdrom_type
      # set boot flag, if needed
      boot_val = ""
      if boot_cdrom:
        kvm_cmd.extend(["-boot", "d"])
        if needs_boot_flag:
          boot_val = ",boot=on"
      # and finally build the entire '-drive' value
      drive_val = "file=%s%s%s%s" % (iso_image, options, if_val, boot_val)
      kvm_cmd.extend(["-drive", drive_val])

    iso_image2 = hvp[constants.HV_KVM_CDROM2_IMAGE_PATH]
    if iso_image2:
      options = ",format=raw,media=cdrom"
      if cdrom_disk_type == constants.HT_DISK_PARAVIRTUAL:
        if_val = ",if=virtio"
      else:
        if_val = ",if=%s" % cdrom_disk_type
      drive_val = "file=%s%s%s" % (iso_image2, options, if_val)
      kvm_cmd.extend(["-drive", drive_val])

    floppy_image = hvp[constants.HV_KVM_FLOPPY_IMAGE_PATH]
    if floppy_image:
      options = ",format=raw,media=disk"
      if boot_floppy:
        kvm_cmd.extend(["-boot", "a"])
        options = "%s,boot=on" % options
      if_val = ",if=floppy"
      options = "%s%s" % (options, if_val)
      drive_val = "file=%s%s" % (floppy_image, options)
      kvm_cmd.extend(["-drive", drive_val])

    if kernel_path:
      kvm_cmd.extend(["-kernel", kernel_path])
      initrd_path = hvp[constants.HV_INITRD_PATH]
      if initrd_path:
        kvm_cmd.extend(["-initrd", initrd_path])
      root_append = ["root=%s" % hvp[constants.HV_ROOT_PATH],
                     hvp[constants.HV_KERNEL_ARGS]]
      if hvp[constants.HV_SERIAL_CONSOLE]:
        serial_speed = hvp[constants.HV_SERIAL_SPEED]
        root_append.append("console=ttyS0,%s" % serial_speed)
      kvm_cmd.extend(["-append", " ".join(root_append)])

    mem_path = hvp[constants.HV_MEM_PATH]
    if mem_path:
      kvm_cmd.extend(["-mem-path", mem_path, "-mem-prealloc"])

    monitor_dev = ("unix:%s,server,nowait" %
                   self._InstanceMonitor(instance.name))
    kvm_cmd.extend(["-monitor", monitor_dev])
    if hvp[constants.HV_SERIAL_CONSOLE]:
      serial_dev = ("unix:%s,server,nowait" %
                    self._InstanceSerial(instance.name))
      kvm_cmd.extend(["-serial", serial_dev])
    else:
      kvm_cmd.extend(["-serial", "none"])

    mouse_type = hvp[constants.HV_USB_MOUSE]
    vnc_bind_address = hvp[constants.HV_VNC_BIND_ADDRESS]
    spice_bind = hvp[constants.HV_KVM_SPICE_BIND]
    spice_ip_version = None

    kvm_cmd.extend(["-usb"])

    if mouse_type:
      kvm_cmd.extend(["-usbdevice", mouse_type])
    elif vnc_bind_address:
      kvm_cmd.extend(["-usbdevice", constants.HT_MOUSE_TABLET])

    if vnc_bind_address:
      if netutils.IP4Address.IsValid(vnc_bind_address):
        if instance.network_port > constants.VNC_BASE_PORT:
          display = instance.network_port - constants.VNC_BASE_PORT
          if vnc_bind_address == constants.IP4_ADDRESS_ANY:
            vnc_arg = ":%d" % (display)
          else:
            vnc_arg = "%s:%d" % (vnc_bind_address, display)
        else:
          logging.error("Network port is not a valid VNC display (%d < %d),"
                        " not starting VNC",
                        instance.network_port, constants.VNC_BASE_PORT)
          vnc_arg = "none"

        # Only allow tls and other option when not binding to a file, for now.
        # kvm/qemu gets confused otherwise about the filename to use.
        vnc_append = ""
        if hvp[constants.HV_VNC_TLS]:
          vnc_append = "%s,tls" % vnc_append
          if hvp[constants.HV_VNC_X509_VERIFY]:
            vnc_append = "%s,x509verify=%s" % (vnc_append,
                                               hvp[constants.HV_VNC_X509])
          elif hvp[constants.HV_VNC_X509]:
            vnc_append = "%s,x509=%s" % (vnc_append,
                                         hvp[constants.HV_VNC_X509])
        if hvp[constants.HV_VNC_PASSWORD_FILE]:
          vnc_append = "%s,password" % vnc_append

        vnc_arg = "%s%s" % (vnc_arg, vnc_append)

      else:
        vnc_arg = "unix:%s/%s.vnc" % (vnc_bind_address, instance.name)

      kvm_cmd.extend(["-vnc", vnc_arg])
    elif spice_bind:
      # FIXME: this is wrong here; the iface ip address differs
      # between systems, so it should be done in _ExecuteKVMRuntime
      if netutils.IsValidInterface(spice_bind):
        # The user specified a network interface, we have to figure out the IP
        # address.
        addresses = netutils.GetInterfaceIpAddresses(spice_bind)
        spice_ip_version = hvp[constants.HV_KVM_SPICE_IP_VERSION]

        # if the user specified an IP version and the interface does not
        # have that kind of IP addresses, throw an exception
        if spice_ip_version != constants.IFACE_NO_IP_VERSION_SPECIFIED:
          if not addresses[spice_ip_version]:
            raise errors.HypervisorError("SPICE: Unable to get an IPv%s address"
                                         " for %s" % (spice_ip_version,
                                                      spice_bind))

        # the user did not specify an IP version, we have to figure it out
        elif (addresses[constants.IP4_VERSION] and
              addresses[constants.IP6_VERSION]):
          # we have both ipv4 and ipv6, let's use the cluster default IP
          # version
          cluster_family = ssconf.SimpleStore().GetPrimaryIPFamily()
          spice_ip_version = \
            netutils.IPAddress.GetVersionFromAddressFamily(cluster_family)
        elif addresses[constants.IP4_VERSION]:
          spice_ip_version = constants.IP4_VERSION
        elif addresses[constants.IP6_VERSION]:
          spice_ip_version = constants.IP6_VERSION
        else:
          raise errors.HypervisorError("SPICE: Unable to get an IP address"
                                       " for %s" % (spice_bind))

        spice_address = addresses[spice_ip_version][0]

      else:
        # spice_bind is known to be a valid IP address, because
        # ValidateParameters checked it.
        spice_address = spice_bind

      spice_arg = "addr=%s" % spice_address
      if hvp[constants.HV_KVM_SPICE_USE_TLS]:
        spice_arg = ("%s,tls-port=%s,x509-cacert-file=%s" %
                     (spice_arg, instance.network_port,
                      pathutils.SPICE_CACERT_FILE))
        spice_arg = ("%s,x509-key-file=%s,x509-cert-file=%s" %
                     (spice_arg, pathutils.SPICE_CERT_FILE,
                      pathutils.SPICE_CERT_FILE))
        tls_ciphers = hvp[constants.HV_KVM_SPICE_TLS_CIPHERS]
        if tls_ciphers:
          spice_arg = "%s,tls-ciphers=%s" % (spice_arg, tls_ciphers)
      else:
        spice_arg = "%s,port=%s" % (spice_arg, instance.network_port)

      if not hvp[constants.HV_KVM_SPICE_PASSWORD_FILE]:
        spice_arg = "%s,disable-ticketing" % spice_arg

      if spice_ip_version:
        spice_arg = "%s,ipv%s" % (spice_arg, spice_ip_version)

      # Image compression options
      img_lossless = hvp[constants.HV_KVM_SPICE_LOSSLESS_IMG_COMPR]
      img_jpeg = hvp[constants.HV_KVM_SPICE_JPEG_IMG_COMPR]
      img_zlib_glz = hvp[constants.HV_KVM_SPICE_ZLIB_GLZ_IMG_COMPR]
      if img_lossless:
        spice_arg = "%s,image-compression=%s" % (spice_arg, img_lossless)
      if img_jpeg:
        spice_arg = "%s,jpeg-wan-compression=%s" % (spice_arg, img_jpeg)
      if img_zlib_glz:
        spice_arg = "%s,zlib-glz-wan-compression=%s" % (spice_arg, img_zlib_glz)

      # Video stream detection
      video_streaming = hvp[constants.HV_KVM_SPICE_STREAMING_VIDEO_DETECTION]
      if video_streaming:
        spice_arg = "%s,streaming-video=%s" % (spice_arg, video_streaming)

      # Audio compression, by default in qemu-kvm it is on
      if not hvp[constants.HV_KVM_SPICE_AUDIO_COMPR]:
        spice_arg = "%s,playback-compression=off" % spice_arg
      if not hvp[constants.HV_KVM_SPICE_USE_VDAGENT]:
        spice_arg = "%s,agent-mouse=off" % spice_arg
      else:
        # Enable the spice agent communication channel between the host and the
        # agent.
        kvm_cmd.extend(["-device", "virtio-serial-pci"])
        kvm_cmd.extend([
          "-device",
          "virtserialport,chardev=spicechannel0,name=com.redhat.spice.0",
          ])
        kvm_cmd.extend(["-chardev", "spicevmc,id=spicechannel0,name=vdagent"])

      logging.info("KVM: SPICE will listen on port %s", instance.network_port)
      kvm_cmd.extend(["-spice", spice_arg])

    else:
      # From qemu 1.4 -nographic is incompatible with -daemonize. The new way
      # also works in earlier versions though (tested with 1.1 and 1.3)
      if self._DISPLAY_RE.search(kvmhelp):
        kvm_cmd.extend(["-display", "none"])
      else:
        kvm_cmd.extend(["-nographic"])

    if hvp[constants.HV_USE_LOCALTIME]:
      kvm_cmd.extend(["-localtime"])

    if hvp[constants.HV_KVM_USE_CHROOT]:
      kvm_cmd.extend(["-chroot", self._InstanceChrootDir(instance.name)])

    # Add qemu-KVM -cpu param
    if hvp[constants.HV_CPU_TYPE]:
      kvm_cmd.extend(["-cpu", hvp[constants.HV_CPU_TYPE]])

    # As requested by music lovers
    if hvp[constants.HV_SOUNDHW]:
      kvm_cmd.extend(["-soundhw", hvp[constants.HV_SOUNDHW]])

    # Pass a -vga option if requested, or if spice is used, for backwards
    # compatibility.
    if hvp[constants.HV_VGA]:
      kvm_cmd.extend(["-vga", hvp[constants.HV_VGA]])
    elif spice_bind:
      kvm_cmd.extend(["-vga", "qxl"])

    # Various types of usb devices, comma separated
    if hvp[constants.HV_USB_DEVICES]:
      for dev in hvp[constants.HV_USB_DEVICES].split(","):
        kvm_cmd.extend(["-usbdevice", dev])

    if hvp[constants.HV_KVM_EXTRA]:
      kvm_cmd.extend(hvp[constants.HV_KVM_EXTRA].split(" "))

    pci_reservations = bitarray(self._DEFAULT_PCI_RESERVATIONS)
    kvm_disks = []
    for disk, link_name in block_devices:
      _UpdatePCISlots(disk, pci_reservations)
      kvm_disks.append((disk, link_name))

    kvm_nics = []
    for nic in instance.nics:
      _UpdatePCISlots(nic, pci_reservations)
      kvm_nics.append(nic)

    hvparams = hvp

    return (kvm_cmd, kvm_nics, hvparams, kvm_disks)

  def _WriteKVMRuntime(self, instance_name, data):
    """Write an instance's KVM runtime

    """
    try:
      utils.WriteFile(self._InstanceKVMRuntime(instance_name),
                      data=data)
    except EnvironmentError, err:
      raise errors.HypervisorError("Failed to save KVM runtime file: %s" % err)

  @classmethod
  def _ReadKVMRuntime(cls, instance_name):
    """Read an instance's KVM runtime

    """
    try:
      file_content = utils.ReadFile(cls._InstanceKVMRuntime(instance_name))
    except EnvironmentError, err:
      raise errors.HypervisorError("Failed to load KVM runtime file: %s" % err)
    return file_content

  def _SaveKVMRuntime(self, instance, kvm_runtime):
    """Save an instance's KVM runtime

    """
    kvm_cmd, kvm_nics, hvparams, kvm_disks = kvm_runtime

    serialized_nics = [nic.ToDict() for nic in kvm_nics]
    serialized_disks = [(blk.ToDict(), link)
                            for blk, link in kvm_disks]
    serialized_form = serializer.Dump((kvm_cmd, serialized_nics, hvparams,
                                      serialized_disks))

    self._WriteKVMRuntime(instance.name, serialized_form)

  @classmethod
  def _LoadKVMRuntime(cls, instance_name, serialized_runtime=None):
    """Load an instance's KVM runtime

    """
    if not serialized_runtime:
      serialized_runtime = cls._ReadKVMRuntime(instance_name)

    return _AnalyzeSerializedRuntime(serialized_runtime)

  def _RunKVMCmd(self, name, kvm_cmd, tap_fds=None):
    """Run the KVM cmd and check for errors

    @type name: string
    @param name: instance name
    @type kvm_cmd: list of strings
    @param kvm_cmd: runcmd input for kvm
    @type tap_fds: list of int
    @param tap_fds: fds of tap devices opened by Ganeti

    """
    try:
      result = utils.RunCmd(kvm_cmd, noclose_fds=tap_fds)
    finally:
      for fd in tap_fds:
        utils_wrapper.CloseFdNoError(fd)

    if result.failed:
      raise errors.HypervisorError("Failed to start instance %s: %s (%s)" %
                                   (name, result.fail_reason, result.output))
    if not self._InstancePidAlive(name)[2]:
      raise errors.HypervisorError("Failed to start instance %s" % name)

  # too many local variables
  # pylint: disable=R0914
  def _ExecuteKVMRuntime(self, instance, kvm_runtime, kvmhelp, incoming=None):
    """Execute a KVM cmd, after completing it with some last minute data.

    @type incoming: tuple of strings
    @param incoming: (target_host_ip, port)
    @type kvmhelp: string
    @param kvmhelp: output of kvm --help

    """
    # Small _ExecuteKVMRuntime hv parameters programming howto:
    #  - conf_hvp contains the parameters as configured on ganeti. they might
    #    have changed since the instance started; only use them if the change
    #    won't affect the inside of the instance (which hasn't been rebooted).
    #  - up_hvp contains the parameters as they were when the instance was
    #    started, plus any new parameter which has been added between ganeti
    #    versions: it is paramount that those default to a value which won't
    #    affect the inside of the instance as well.
    conf_hvp = instance.hvparams
    name = instance.name
    self._CheckDown(name)

    temp_files = []

    kvm_cmd, kvm_nics, up_hvp, kvm_disks = kvm_runtime
    # the first element of kvm_cmd is always the path to the kvm binary
    kvm_path = kvm_cmd[0]
    up_hvp = objects.FillDict(conf_hvp, up_hvp)

    # We know it's safe to run as a different user upon migration, so we'll use
    # the latest conf, from conf_hvp.
    security_model = conf_hvp[constants.HV_SECURITY_MODEL]
    if security_model == constants.HT_SM_USER:
      kvm_cmd.extend(["-runas", conf_hvp[constants.HV_SECURITY_DOMAIN]])

    keymap = conf_hvp[constants.HV_KEYMAP]
    if keymap:
      keymap_path = self._InstanceKeymapFile(name)
      # If a keymap file is specified, KVM won't use its internal defaults. By
      # first including the "en-us" layout, an error on loading the actual
      # layout (e.g. because it can't be found) won't lead to a non-functional
      # keyboard. A keyboard with incorrect keys is still better than none.
      utils.WriteFile(keymap_path, data="include en-us\ninclude %s\n" % keymap)
      kvm_cmd.extend(["-k", keymap_path])

    # We have reasons to believe changing something like the nic driver/type
    # upon migration won't exactly fly with the instance kernel, so for nic
    # related parameters we'll use up_hvp
    tapfds = []
    taps = []
    devlist = self._GetKVMOutput(kvm_path, self._KVMOPT_DEVICELIST)

    bdev_opts = self._GenerateKVMBlockDevicesOptions(instance,
                                                     kvm_disks,
                                                     kvmhelp,
                                                     devlist)
    kvm_cmd.extend(bdev_opts)

    if not kvm_nics:
      kvm_cmd.extend(["-net", "none"])
    else:
      vnet_hdr = False
      tap_extra = ""
      nic_type = up_hvp[constants.HV_NIC_TYPE]
      if nic_type == constants.HT_NIC_PARAVIRTUAL:
        nic_model = self._VIRTIO
        try:
          if self._VIRTIO_NET_RE.search(devlist):
            nic_model = self._VIRTIO_NET_PCI
            vnet_hdr = up_hvp[constants.HV_VNET_HDR]
        except errors.HypervisorError, _:
          # Older versions of kvm don't support DEVICE_LIST, but they don't
          # have new virtio syntax either.
          pass

        if up_hvp[constants.HV_VHOST_NET]:
          # check for vhost_net support
          if self._VHOST_RE.search(kvmhelp):
            tap_extra = ",vhost=on"
          else:
            raise errors.HypervisorError("vhost_net is configured"
                                         " but it is not available")
      else:
        nic_model = nic_type

      kvm_supports_netdev = self._NETDEV_RE.search(kvmhelp)

      for nic_seq, nic in enumerate(kvm_nics):
        tapname, tapfd = _OpenTap(vnet_hdr=vnet_hdr)
        tapfds.append(tapfd)
        taps.append(tapname)
        if kvm_supports_netdev:
          nic_val = "%s,mac=%s" % (nic_model, nic.mac)
          try:
            # kvm_nics already exist in old runtime files and thus there might
            # be some entries without pci slot (therefore try: except:)
            kvm_devid = _GenerateDeviceKVMId(constants.HOTPLUG_TARGET_NIC, nic)
            netdev = kvm_devid
            nic_val += (",id=%s,bus=pci.0,addr=%s" % (kvm_devid, hex(nic.pci)))
          except errors.HotplugError:
            netdev = "netdev%d" % nic_seq
          nic_val += (",netdev=%s" % netdev)
          tap_val = ("type=tap,id=%s,fd=%d%s" %
                     (netdev, tapfd, tap_extra))
          kvm_cmd.extend(["-netdev", tap_val, "-device", nic_val])
        else:
          nic_val = "nic,vlan=%s,macaddr=%s,model=%s" % (nic_seq,
                                                         nic.mac, nic_model)
          tap_val = "tap,vlan=%s,fd=%d" % (nic_seq, tapfd)
          kvm_cmd.extend(["-net", tap_val, "-net", nic_val])

    if incoming:
      target, port = incoming
      kvm_cmd.extend(["-incoming", "tcp:%s:%s" % (target, port)])

    # Changing the vnc password doesn't bother the guest that much. At most it
    # will surprise people who connect to it. Whether positively or negatively
    # it's debatable.
    vnc_pwd_file = conf_hvp[constants.HV_VNC_PASSWORD_FILE]
    vnc_pwd = None
    if vnc_pwd_file:
      try:
        vnc_pwd = utils.ReadOneLineFile(vnc_pwd_file, strict=True)
      except EnvironmentError, err:
        raise errors.HypervisorError("Failed to open VNC password file %s: %s"
                                     % (vnc_pwd_file, err))

    if conf_hvp[constants.HV_KVM_USE_CHROOT]:
      utils.EnsureDirs([(self._InstanceChrootDir(name),
                         constants.SECURE_DIR_MODE)])

    # Automatically enable QMP if version is >= 0.14
    if self._QMP_RE.search(kvmhelp):
      logging.debug("Enabling QMP")
      kvm_cmd.extend(["-qmp", "unix:%s,server,nowait" %
                      self._InstanceQmpMonitor(instance.name)])

    # Configure the network now for starting instances and bridged interfaces,
    # during FinalizeMigration for incoming instances' routed interfaces
    for nic_seq, nic in enumerate(kvm_nics):
      if (incoming and
          nic.nicparams[constants.NIC_MODE] != constants.NIC_MODE_BRIDGED):
        continue
      self._ConfigureNIC(instance, nic_seq, nic, taps[nic_seq])

    # CPU affinity requires kvm to start paused, so we set this flag if the
    # instance is not already paused and if we are not going to accept a
    # migrating instance. In the latter case, pausing is not needed.
    start_kvm_paused = not (_KVM_START_PAUSED_FLAG in kvm_cmd) and not incoming
    if start_kvm_paused:
      kvm_cmd.extend([_KVM_START_PAUSED_FLAG])

    # Note: CPU pinning is using up_hvp since changes take effect
    # during instance startup anyway, and to avoid problems when soft
    # rebooting the instance.
    cpu_pinning = False
    if up_hvp.get(constants.HV_CPU_MASK, None):
      cpu_pinning = True

    if security_model == constants.HT_SM_POOL:
      ss = ssconf.SimpleStore()
      uid_pool = uidpool.ParseUidPool(ss.GetUidPool(), separator="\n")
      all_uids = set(uidpool.ExpandUidPool(uid_pool))
      uid = uidpool.RequestUnusedUid(all_uids)
      try:
        username = pwd.getpwuid(uid.GetUid()).pw_name
        kvm_cmd.extend(["-runas", username])
        self._RunKVMCmd(name, kvm_cmd, tapfds)
      except:
        uidpool.ReleaseUid(uid)
        raise
      else:
        uid.Unlock()
        utils.WriteFile(self._InstanceUidFile(name), data=uid.AsStr())
    else:
      self._RunKVMCmd(name, kvm_cmd, tapfds)

    utils.EnsureDirs([(self._InstanceNICDir(instance.name),
                     constants.RUN_DIRS_MODE)])
    for nic_seq, tap in enumerate(taps):
      nic = kvm_nics[nic_seq]
      self._WriteInstanceNICFiles(instance.name, nic_seq, nic, tap)

    if vnc_pwd:
      change_cmd = "change vnc password %s" % vnc_pwd
      self._CallMonitorCommand(instance.name, change_cmd)

    # Setting SPICE password. We are not vulnerable to malicious passwordless
    # connection attempts because SPICE by default does not allow connections
    # if neither a password nor the "disable_ticketing" options are specified.
    # As soon as we send the password via QMP, that password is a valid ticket
    # for connection.
    spice_password_file = conf_hvp[constants.HV_KVM_SPICE_PASSWORD_FILE]
    if spice_password_file:
      spice_pwd = ""
      try:
        spice_pwd = utils.ReadOneLineFile(spice_password_file, strict=True)
      except EnvironmentError, err:
        raise errors.HypervisorError("Failed to open SPICE password file %s: %s"
                                     % (spice_password_file, err))

      qmp = QmpConnection(self._InstanceQmpMonitor(instance.name))
      qmp.connect()
      arguments = {
          "protocol": "spice",
          "password": spice_pwd,
      }
      qmp.Execute("set_password", arguments)

    for filename in temp_files:
      utils.RemoveFile(filename)

    # If requested, set CPU affinity and resume instance execution
    if cpu_pinning:
      self._ExecuteCpuAffinity(instance.name, up_hvp[constants.HV_CPU_MASK])

    start_memory = self._InstanceStartupMemory(instance)
    if start_memory < instance.beparams[constants.BE_MAXMEM]:
      self.BalloonInstanceMemory(instance, start_memory)

    if start_kvm_paused:
      # To control CPU pinning, ballooning, and vnc/spice passwords
      # the VM was started in a frozen state. If freezing was not
      # explicitly requested resume the vm status.
      self._CallMonitorCommand(instance.name, self._CONT_CMD)

  def StartInstance(self, instance, block_devices, startup_paused):
    """Start an instance.

    """
    self._CheckDown(instance.name)
    kvmpath = instance.hvparams[constants.HV_KVM_PATH]
    kvmhelp = self._GetKVMOutput(kvmpath, self._KVMOPT_HELP)
    kvm_runtime = self._GenerateKVMRuntime(instance, block_devices,
                                           startup_paused, kvmhelp)
    self._SaveKVMRuntime(instance, kvm_runtime)
    self._ExecuteKVMRuntime(instance, kvm_runtime, kvmhelp)

  def _CallMonitorCommand(self, instance_name, command, timeout=None):
    """Invoke a command on the instance monitor.

    """
    if timeout is not None:
      timeout_cmd = "timeout %s" % (timeout, )
    else:
      timeout_cmd = ""

    # TODO: Replace monitor calls with QMP once KVM >= 0.14 is the minimum
    # version. The monitor protocol is designed for human consumption, whereas
    # QMP is made for programmatic usage. In the worst case QMP can also
    # execute monitor commands. As it is, all calls to socat take at least
    # 500ms and likely more: socat can't detect the end of the reply and waits
    # for 500ms of no data received before exiting (500 ms is the default for
    # the "-t" parameter).
    socat = ("echo %s | %s %s STDIO UNIX-CONNECT:%s" %
             (utils.ShellQuote(command),
              timeout_cmd,
              constants.SOCAT_PATH,
              utils.ShellQuote(self._InstanceMonitor(instance_name))))

    result = utils.RunCmd(socat)
    if result.failed:
      msg = ("Failed to send command '%s' to instance '%s', reason '%s',"
             " output: %s" %
             (command, instance_name, result.fail_reason, result.output))
      raise errors.HypervisorError(msg)

    return result

  def _GetFreePCISlot(self, instance, dev):
    """Get the first available pci slot of a runnung instance.

    """
    slots = bitarray(32)
    slots.setall(False) # pylint: disable=E1101
    output = self._CallMonitorCommand(instance.name, self._INFO_PCI_CMD)
    for line in output.stdout.splitlines():
      match = self._INFO_PCI_RE.search(line)
      if match:
        slot = int(match.group(1))
        slots[slot] = True

    [free] = slots.search(_AVAILABLE_PCI_SLOT, 1) # pylint: disable=E1101
    if not free:
      raise errors.HypervisorError("All PCI slots occupied")

    dev.pci = int(free)

  def VerifyHotplugSupport(self, instance, action, dev_type):
    """Verifies that hotplug is supported.

    Hotplug is *not* supported in case of:
     - security models and chroot (disk hotplug)
     - fdsend module is missing (nic hot-add)

    @raise errors.HypervisorError: in one of the previous cases

    """
    if dev_type == constants.HOTPLUG_TARGET_DISK:
      hvp = instance.hvparams
      security_model = hvp[constants.HV_SECURITY_MODEL]
      use_chroot = hvp[constants.HV_KVM_USE_CHROOT]
      if use_chroot:
        raise errors.HotplugError("Disk hotplug is not supported"
                                  " in case of chroot.")
      if security_model != constants.HT_SM_NONE:
        raise errors.HotplugError("Disk Hotplug is not supported in case"
                                  " security models are used.")

    if (dev_type == constants.HOTPLUG_TARGET_NIC and
        action == constants.HOTPLUG_ACTION_ADD and not fdsend):
      raise errors.HotplugError("Cannot hot-add NIC."
                                " fdsend python module is missing.")

  def HotplugSupported(self, instance):
    """Checks if hotplug is generally supported.

    Hotplug is *not* supported in case of:
     - qemu versions < 1.0
     - for stopped instances

    @raise errors.HypervisorError: in one of the previous cases

    """
    try:
      output = self._CallMonitorCommand(instance.name, self._INFO_VERSION_CMD)
    except errors.HypervisorError:
      raise errors.HotplugError("Instance is probably down")

    # TODO: search for netdev_add, drive_add, device_add.....
    match = self._INFO_VERSION_RE.search(output.stdout)
    if not match:
      raise errors.HotplugError("Cannot parse qemu version via monitor")

    v_major, v_min, _, _ = match.groups()
    if (int(v_major), int(v_min)) < (1, 0):
      raise errors.HotplugError("Hotplug not supported for qemu versions < 1.0")

  def _CallHotplugCommands(self, name, cmds):
    for c in cmds:
      self._CallMonitorCommand(name, c)
      time.sleep(1)

  def _VerifyHotplugCommand(self, instance_name, device, dev_type,
                            should_exist):
    """Checks if a previous hotplug command has succeeded.

    It issues info pci monitor command and checks depending on should_exist
    value if an entry with PCI slot and device ID is found or not.

    @raise errors.HypervisorError: if result is not the expected one

    """
    output = self._CallMonitorCommand(instance_name, self._INFO_PCI_CMD)
    kvm_devid = _GenerateDeviceKVMId(dev_type, device)
    match = \
      self._FIND_PCI_DEVICE_RE(device.pci, kvm_devid).search(output.stdout)
    if match and not should_exist:
      msg = "Device %s should have been removed but is still there" % kvm_devid
      raise errors.HypervisorError(msg)

    if not match and should_exist:
      msg = "Device %s should have been added but is missing" % kvm_devid
      raise errors.HypervisorError(msg)

    logging.info("Device %s has been correctly hot-plugged", kvm_devid)

  def HotAddDevice(self, instance, dev_type, device, extra, seq):
    """ Helper method to hot-add a new device

    It gets free pci slot generates the device name and invokes the
    device specific method.

    """
    # in case of hot-mod this is given
    if device.pci is None:
      self._GetFreePCISlot(instance, device)
    kvm_devid = _GenerateDeviceKVMId(dev_type, device)
    runtime = self._LoadKVMRuntime(instance.name)
    if dev_type == constants.HOTPLUG_TARGET_DISK:
      cmds = ["drive_add dummy file=%s,if=none,id=%s,format=raw" %
                (extra, kvm_devid)]
      cmds += ["device_add virtio-blk-pci,bus=pci.0,addr=%s,drive=%s,id=%s" %
                (hex(device.pci), kvm_devid, kvm_devid)]
    elif dev_type == constants.HOTPLUG_TARGET_NIC:
      (tap, fd) = _OpenTap()
      self._ConfigureNIC(instance, seq, device, tap)
      self._PassTapFd(instance, fd, device)
      cmds = ["netdev_add tap,id=%s,fd=%s" % (kvm_devid, kvm_devid)]
      args = "virtio-net-pci,bus=pci.0,addr=%s,mac=%s,netdev=%s,id=%s" % \
               (hex(device.pci), device.mac, kvm_devid, kvm_devid)
      cmds += ["device_add %s" % args]
      self._WriteInstanceNICFiles(instance.name, seq, device, tap)

    self._CallHotplugCommands(instance.name, cmds)
    self._VerifyHotplugCommand(instance.name, device, dev_type, True)
    # update relevant entries in runtime file
    index = _DEVICE_RUNTIME_INDEX[dev_type]
    entry = _RUNTIME_ENTRY[dev_type](device, extra)
    runtime[index].append(entry)
    self._SaveKVMRuntime(instance, runtime)

  def HotDelDevice(self, instance, dev_type, device, _, seq):
    """ Helper method for hot-del device

    It gets device info from runtime file, generates the device name and
    invokes the device specific method.

    """
    runtime = self._LoadKVMRuntime(instance.name)
    entry = _GetExistingDeviceInfo(dev_type, device, runtime)
    kvm_device = _RUNTIME_DEVICE[dev_type](entry)
    kvm_devid = _GenerateDeviceKVMId(dev_type, kvm_device)
    if dev_type == constants.HOTPLUG_TARGET_DISK:
      cmds = ["device_del %s" % kvm_devid]
      cmds += ["drive_del %s" % kvm_devid]
    elif dev_type == constants.HOTPLUG_TARGET_NIC:
      cmds = ["device_del %s" % kvm_devid]
      cmds += ["netdev_del %s" % kvm_devid]
      self._UnconfigureNic(instance.name, kvm_device, False)
      self._RemoveInstanceNICFiles(instance.name, seq, device)
    self._CallHotplugCommands(instance.name, cmds)
    self._VerifyHotplugCommand(instance.name, kvm_device, dev_type, False)
    index = _DEVICE_RUNTIME_INDEX[dev_type]
    runtime[index].remove(entry)
    self._SaveKVMRuntime(instance, runtime)

    return kvm_device.pci

  def HotModDevice(self, instance, dev_type, device, _, seq):
    """ Helper method for hot-mod device

    It gets device info from runtime file, generates the device name and
    invokes the device specific method. Currently only NICs support hot-mod

    """
    if dev_type == constants.HOTPLUG_TARGET_NIC:
      # putting it back in the same pci slot
      device.pci = self.HotDelDevice(instance, dev_type, device, _, seq)
      # TODO: remove sleep when socat gets removed
      self.HotAddDevice(instance, dev_type, device, _, seq)

  def _PassTapFd(self, instance, fd, nic):
    """Pass file descriptor to kvm process via monitor socket using SCM_RIGHTS

    """
    # TODO: factor out code related to unix sockets.
    #       squash common parts between monitor and qmp
    kvm_devid = _GenerateDeviceKVMId(constants.HOTPLUG_TARGET_NIC, nic)
    command = "getfd %s\n" % kvm_devid
    fds = [fd]
    logging.info("%s", fds)
    try:
      monsock = MonitorSocket(self._InstanceMonitor(instance.name))
      monsock.connect()
      fdsend.sendfds(monsock.sock, command, fds=fds)
    finally:
      monsock.close()

  @classmethod
  def _ParseKVMVersion(cls, text):
    """Parse the KVM version from the --help output.

    @type text: string
    @param text: output of kvm --help
    @return: (version, v_maj, v_min, v_rev)
    @raise errors.HypervisorError: when the KVM version cannot be retrieved

    """
    match = cls._VERSION_RE.search(text.splitlines()[0])
    if not match:
      raise errors.HypervisorError("Unable to get KVM version")

    v_all = match.group(0)
    v_maj = int(match.group(1))
    v_min = int(match.group(2))
    if match.group(4):
      v_rev = int(match.group(4))
    else:
      v_rev = 0
    return (v_all, v_maj, v_min, v_rev)

  @classmethod
  def _GetKVMOutput(cls, kvm_path, option):
    """Return the output of a kvm invocation

    @type kvm_path: string
    @param kvm_path: path to the kvm executable
    @type option: a key of _KVMOPTS_CMDS
    @param option: kvm option to fetch the output from
    @return: output a supported kvm invocation
    @raise errors.HypervisorError: when the KVM help output cannot be retrieved

    """
    assert option in cls._KVMOPTS_CMDS, "Invalid output option"

    optlist, can_fail = cls._KVMOPTS_CMDS[option]

    result = utils.RunCmd([kvm_path] + optlist)
    if result.failed and not can_fail:
      raise errors.HypervisorError("Unable to get KVM %s output" %
                                    " ".join(optlist))
    return result.output

  @classmethod
  def _GetKVMVersion(cls, kvm_path):
    """Return the installed KVM version.

    @return: (version, v_maj, v_min, v_rev)
    @raise errors.HypervisorError: when the KVM version cannot be retrieved

    """
    return cls._ParseKVMVersion(cls._GetKVMOutput(kvm_path, cls._KVMOPT_HELP))

  @classmethod
  def _GetDefaultMachineVersion(cls, kvm_path):
    """Return the default hardware revision (e.g. pc-1.1)

    """
    output = cls._GetKVMOutput(kvm_path, cls._KVMOPT_MLIST)
    match = cls._DEFAULT_MACHINE_VERSION_RE.search(output)
    if match:
      return match.group(1)
    else:
      return "pc"

  def StopInstance(self, instance, force=False, retry=False, name=None,
                   timeout=None):
    """Stop an instance.

    """
    assert(timeout is None or force is not None)

    if name is not None and not force:
      raise errors.HypervisorError("Cannot shutdown cleanly by name only")
    if name is None:
      name = instance.name
      acpi = instance.hvparams[constants.HV_ACPI]
    else:
      acpi = False
    _, pid, alive = self._InstancePidAlive(name)
    if pid > 0 and alive:
      if force or not acpi:
        utils.KillProcess(pid)
      else:
        self._CallMonitorCommand(name, "system_powerdown", timeout)

  @classmethod
  def _UnconfigureInstanceNICs(cls, instance_name, info=None):
    """Get runtime NICs of an instance and unconfigure them

    """
    _, kvm_nics, __, ___ = cls._LoadKVMRuntime(instance_name, info)
    for nic in kvm_nics:
      cls._UnconfigureNic(instance_name, nic)

  def CleanupInstance(self, instance_name):
    """Cleanup after a stopped instance

    """
    pidfile, pid, alive = self._InstancePidAlive(instance_name)
    if pid > 0 and alive:
      raise errors.HypervisorError("Cannot cleanup a live instance")
    self._RemoveInstanceRuntimeFiles(pidfile, instance_name)

  def RebootInstance(self, instance):
    """Reboot an instance.

    """
    # For some reason if we do a 'send-key ctrl-alt-delete' to the control
    # socket the instance will stop, but now power up again. So we'll resort
    # to shutdown and restart.
    _, _, alive = self._InstancePidAlive(instance.name)
    if not alive:
      raise errors.HypervisorError("Failed to reboot instance %s:"
                                   " not running" % instance.name)
    # StopInstance will delete the saved KVM runtime so:
    # ...first load it...
    kvm_runtime = self._LoadKVMRuntime(instance.name)
    # ...now we can safely call StopInstance...
    if not self.StopInstance(instance):
      self.StopInstance(instance, force=True)
    # ...and finally we can save it again, and execute it...
    self._SaveKVMRuntime(instance, kvm_runtime)
    kvmpath = instance.hvparams[constants.HV_KVM_PATH]
    kvmhelp = self._GetKVMOutput(kvmpath, self._KVMOPT_HELP)
    self._ExecuteKVMRuntime(instance, kvm_runtime, kvmhelp)

  def MigrationInfo(self, instance):
    """Get instance information to perform a migration.

    @type instance: L{objects.Instance}
    @param instance: instance to be migrated
    @rtype: string
    @return: content of the KVM runtime file

    """
    return self._ReadKVMRuntime(instance.name)

  def AcceptInstance(self, instance, info, target):
    """Prepare to accept an instance.

    @type instance: L{objects.Instance}
    @param instance: instance to be accepted
    @type info: string
    @param info: content of the KVM runtime file on the source node
    @type target: string
    @param target: target host (usually ip), on this node

    """
    kvm_runtime = self._LoadKVMRuntime(instance.name, serialized_runtime=info)
    incoming_address = (target, instance.hvparams[constants.HV_MIGRATION_PORT])
    kvmpath = instance.hvparams[constants.HV_KVM_PATH]
    kvmhelp = self._GetKVMOutput(kvmpath, self._KVMOPT_HELP)
    self._ExecuteKVMRuntime(instance, kvm_runtime, kvmhelp,
                            incoming=incoming_address)

  def FinalizeMigrationDst(self, instance, info, success):
    """Finalize the instance migration on the target node.

    Stop the incoming mode KVM.

    @type instance: L{objects.Instance}
    @param instance: instance whose migration is being finalized

    """
    if success:
      kvm_runtime = self._LoadKVMRuntime(instance.name, serialized_runtime=info)
      kvm_nics = kvm_runtime[1]

      for nic_seq, nic in enumerate(kvm_nics):
        if nic.nicparams[constants.NIC_MODE] == constants.NIC_MODE_BRIDGED:
          # Bridged interfaces have already been configured
          continue
        try:
          tap = utils.ReadFile(self._InstanceNICFile(instance.name, nic_seq))
        except EnvironmentError, err:
          logging.warning("Failed to find host interface for %s NIC #%d: %s",
                          instance.name, nic_seq, str(err))
          continue
        try:
          self._ConfigureNIC(instance, nic_seq, nic, tap)
        except errors.HypervisorError, err:
          logging.warning(str(err))

      self._WriteKVMRuntime(instance.name, info)
    else:
      self._UnconfigureInstanceNICs(instance.name, info)
      self.StopInstance(instance, force=True)

  def MigrateInstance(self, instance, target, live):
    """Migrate an instance to a target node.

    The migration will not be attempted if the instance is not
    currently running.

    @type instance: L{objects.Instance}
    @param instance: the instance to be migrated
    @type target: string
    @param target: ip address of the target node
    @type live: boolean
    @param live: perform a live migration

    """
    instance_name = instance.name
    port = instance.hvparams[constants.HV_MIGRATION_PORT]
    _, _, alive = self._InstancePidAlive(instance_name)
    if not alive:
      raise errors.HypervisorError("Instance not running, cannot migrate")

    if not live:
      self._CallMonitorCommand(instance_name, "stop")

    migrate_command = ("migrate_set_speed %dm" %
                       instance.hvparams[constants.HV_MIGRATION_BANDWIDTH])
    self._CallMonitorCommand(instance_name, migrate_command)

    migrate_command = ("migrate_set_downtime %dms" %
                       instance.hvparams[constants.HV_MIGRATION_DOWNTIME])
    self._CallMonitorCommand(instance_name, migrate_command)

    migrate_command = "migrate -d tcp:%s:%s" % (target, port)
    self._CallMonitorCommand(instance_name, migrate_command)

  def FinalizeMigrationSource(self, instance, success, live):
    """Finalize the instance migration on the source node.

    @type instance: L{objects.Instance}
    @param instance: the instance that was migrated
    @type success: bool
    @param success: whether the migration succeeded or not
    @type live: bool
    @param live: whether the user requested a live migration or not

    """
    if success:
      pidfile, pid, _ = self._InstancePidAlive(instance.name)
      utils.KillProcess(pid)
      self._RemoveInstanceRuntimeFiles(pidfile, instance.name)
    elif live:
      self._CallMonitorCommand(instance.name, self._CONT_CMD)

  def GetMigrationStatus(self, instance):
    """Get the migration status

    @type instance: L{objects.Instance}
    @param instance: the instance that is being migrated
    @rtype: L{objects.MigrationStatus}
    @return: the status of the current migration (one of
             L{constants.HV_MIGRATION_VALID_STATUSES}), plus any additional
             progress info that can be retrieved from the hypervisor

    """
    info_command = "info migrate"
    for _ in range(self._MIGRATION_INFO_MAX_BAD_ANSWERS):
      result = self._CallMonitorCommand(instance.name, info_command)
      match = self._MIGRATION_STATUS_RE.search(result.stdout)
      if not match:
        if not result.stdout:
          logging.info("KVM: empty 'info migrate' result")
        else:
          logging.warning("KVM: unknown 'info migrate' result: %s",
                          result.stdout)
      else:
        status = match.group(1)
        if status in constants.HV_KVM_MIGRATION_VALID_STATUSES:
          migration_status = objects.MigrationStatus(status=status)
          match = self._MIGRATION_PROGRESS_RE.search(result.stdout)
          if match:
            migration_status.transferred_ram = match.group("transferred")
            migration_status.total_ram = match.group("total")

          return migration_status

        logging.warning("KVM: unknown migration status '%s'", status)

      time.sleep(self._MIGRATION_INFO_RETRY_DELAY)

    return objects.MigrationStatus(status=constants.HV_MIGRATION_FAILED)

  def BalloonInstanceMemory(self, instance, mem):
    """Balloon an instance memory to a certain value.

    @type instance: L{objects.Instance}
    @param instance: instance to be accepted
    @type mem: int
    @param mem: actual memory size to use for instance runtime

    """
    self._CallMonitorCommand(instance.name, "balloon %d" % mem)

  def GetNodeInfo(self):
    """Return information about the node.

    @return: a dict with the following keys (values in MiB):
          - memory_total: the total memory size on the node
          - memory_free: the available memory on the node for instances
          - memory_dom0: the memory used by the node itself, if available
          - hv_version: the hypervisor version in the form (major, minor,
                        revision)

    """
    result = self.GetLinuxNodeInfo()
    # FIXME: this is the global kvm version, but the actual version can be
    # customized as an hv parameter. we should use the nodegroup's default kvm
    # path parameter here.
    _, v_major, v_min, v_rev = self._GetKVMVersion(constants.KVM_PATH)
    result[constants.HV_NODEINFO_KEY_VERSION] = (v_major, v_min, v_rev)
    return result

  @classmethod
  def GetInstanceConsole(cls, instance, hvparams, beparams):
    """Return a command for connecting to the console of an instance.

    """
    if hvparams[constants.HV_SERIAL_CONSOLE]:
      cmd = [pathutils.KVM_CONSOLE_WRAPPER,
             constants.SOCAT_PATH, utils.ShellQuote(instance.name),
             utils.ShellQuote(cls._InstanceMonitor(instance.name)),
             "STDIO,%s" % cls._SocatUnixConsoleParams(),
             "UNIX-CONNECT:%s" % cls._InstanceSerial(instance.name)]
      return objects.InstanceConsole(instance=instance.name,
                                     kind=constants.CONS_SSH,
                                     host=instance.primary_node,
                                     user=constants.SSH_CONSOLE_USER,
                                     command=cmd)

    vnc_bind_address = hvparams[constants.HV_VNC_BIND_ADDRESS]
    if vnc_bind_address and instance.network_port > constants.VNC_BASE_PORT:
      display = instance.network_port - constants.VNC_BASE_PORT
      return objects.InstanceConsole(instance=instance.name,
                                     kind=constants.CONS_VNC,
                                     host=vnc_bind_address,
                                     port=instance.network_port,
                                     display=display)

    spice_bind = hvparams[constants.HV_KVM_SPICE_BIND]
    if spice_bind:
      return objects.InstanceConsole(instance=instance.name,
                                     kind=constants.CONS_SPICE,
                                     host=spice_bind,
                                     port=instance.network_port)

    return objects.InstanceConsole(instance=instance.name,
                                   kind=constants.CONS_MESSAGE,
                                   message=("No serial shell for instance %s" %
                                            instance.name))

  def Verify(self):
    """Verify the hypervisor.

    Check that the required binaries exist.

    @return: Problem description if something is wrong, C{None} otherwise

    """
    msgs = []
    # FIXME: this is the global kvm binary, but the actual path can be
    # customized as an hv parameter; we should use the nodegroup's
    # default kvm path parameter here.
    if not os.path.exists(constants.KVM_PATH):
      msgs.append("The KVM binary ('%s') does not exist" % constants.KVM_PATH)
    if not os.path.exists(constants.SOCAT_PATH):
      msgs.append("The socat binary ('%s') does not exist" %
                  constants.SOCAT_PATH)

    return self._FormatVerifyResults(msgs)

  @classmethod
  def CheckParameterSyntax(cls, hvparams):
    """Check the given parameters for validity.

    @type hvparams:  dict
    @param hvparams: dictionary with parameter names/value
    @raise errors.HypervisorError: when a parameter is not valid

    """
    super(KVMHypervisor, cls).CheckParameterSyntax(hvparams)

    kernel_path = hvparams[constants.HV_KERNEL_PATH]
    if kernel_path:
      if not hvparams[constants.HV_ROOT_PATH]:
        raise errors.HypervisorError("Need a root partition for the instance,"
                                     " if a kernel is defined")

    if (hvparams[constants.HV_VNC_X509_VERIFY] and
        not hvparams[constants.HV_VNC_X509]):
      raise errors.HypervisorError("%s must be defined, if %s is" %
                                   (constants.HV_VNC_X509,
                                    constants.HV_VNC_X509_VERIFY))

    if hvparams[constants.HV_SERIAL_CONSOLE]:
      serial_speed = hvparams[constants.HV_SERIAL_SPEED]
      valid_speeds = constants.VALID_SERIAL_SPEEDS
      if not serial_speed or serial_speed not in valid_speeds:
        raise errors.HypervisorError("Invalid serial console speed, must be"
                                     " one of: %s" %
                                     utils.CommaJoin(valid_speeds))

    boot_order = hvparams[constants.HV_BOOT_ORDER]
    if (boot_order == constants.HT_BO_CDROM and
        not hvparams[constants.HV_CDROM_IMAGE_PATH]):
      raise errors.HypervisorError("Cannot boot from cdrom without an"
                                   " ISO path")

    security_model = hvparams[constants.HV_SECURITY_MODEL]
    if security_model == constants.HT_SM_USER:
      if not hvparams[constants.HV_SECURITY_DOMAIN]:
        raise errors.HypervisorError("A security domain (user to run kvm as)"
                                     " must be specified")
    elif (security_model == constants.HT_SM_NONE or
          security_model == constants.HT_SM_POOL):
      if hvparams[constants.HV_SECURITY_DOMAIN]:
        raise errors.HypervisorError("Cannot have a security domain when the"
                                     " security model is 'none' or 'pool'")

    spice_bind = hvparams[constants.HV_KVM_SPICE_BIND]
    spice_ip_version = hvparams[constants.HV_KVM_SPICE_IP_VERSION]
    if spice_bind:
      if spice_ip_version != constants.IFACE_NO_IP_VERSION_SPECIFIED:
        # if an IP version is specified, the spice_bind parameter must be an
        # IP of that family
        if (netutils.IP4Address.IsValid(spice_bind) and
            spice_ip_version != constants.IP4_VERSION):
          raise errors.HypervisorError("SPICE: Got an IPv4 address (%s), but"
                                       " the specified IP version is %s" %
                                       (spice_bind, spice_ip_version))

        if (netutils.IP6Address.IsValid(spice_bind) and
            spice_ip_version != constants.IP6_VERSION):
          raise errors.HypervisorError("SPICE: Got an IPv6 address (%s), but"
                                       " the specified IP version is %s" %
                                       (spice_bind, spice_ip_version))
    else:
      # All the other SPICE parameters depend on spice_bind being set. Raise an
      # error if any of them is set without it.
      for param in _SPICE_ADDITIONAL_PARAMS:
        if hvparams[param]:
          raise errors.HypervisorError("SPICE: %s requires %s to be set" %
                                       (param, constants.HV_KVM_SPICE_BIND))

  @classmethod
  def ValidateParameters(cls, hvparams):
    """Check the given parameters for validity.

    @type hvparams:  dict
    @param hvparams: dictionary with parameter names/value
    @raise errors.HypervisorError: when a parameter is not valid

    """
    super(KVMHypervisor, cls).ValidateParameters(hvparams)

    kvm_path = hvparams[constants.HV_KVM_PATH]

    security_model = hvparams[constants.HV_SECURITY_MODEL]
    if security_model == constants.HT_SM_USER:
      username = hvparams[constants.HV_SECURITY_DOMAIN]
      try:
        pwd.getpwnam(username)
      except KeyError:
        raise errors.HypervisorError("Unknown security domain user %s"
                                     % username)

    spice_bind = hvparams[constants.HV_KVM_SPICE_BIND]
    if spice_bind:
      # only one of VNC and SPICE can be used currently.
      if hvparams[constants.HV_VNC_BIND_ADDRESS]:
        raise errors.HypervisorError("Both SPICE and VNC are configured, but"
                                     " only one of them can be used at a"
                                     " given time")

      # check that KVM supports SPICE
      kvmhelp = cls._GetKVMOutput(kvm_path, cls._KVMOPT_HELP)
      if not cls._SPICE_RE.search(kvmhelp):
        raise errors.HypervisorError("SPICE is configured, but it is not"
                                     " supported according to 'kvm --help'")

      # if spice_bind is not an IP address, it must be a valid interface
      bound_to_addr = (netutils.IP4Address.IsValid(spice_bind) or
                       netutils.IP6Address.IsValid(spice_bind))
      if not bound_to_addr and not netutils.IsValidInterface(spice_bind):
        raise errors.HypervisorError("SPICE: The %s parameter must be either"
                                     " a valid IP address or interface name" %
                                     constants.HV_KVM_SPICE_BIND)

    machine_version = hvparams[constants.HV_KVM_MACHINE_VERSION]
    if machine_version:
      output = cls._GetKVMOutput(kvm_path, cls._KVMOPT_MLIST)
      if not cls._CHECK_MACHINE_VERSION_RE(machine_version).search(output):
        raise errors.HypervisorError("Unsupported machine version: %s" %
                                     machine_version)

  @classmethod
  def PowercycleNode(cls):
    """KVM powercycle, just a wrapper over Linux powercycle.

    """
    cls.LinuxPowercycle()