gns3-server/gns3server/compute/qemu/qemu_vm.py

# -*- coding: utf-8 -*-
#
# Copyright (C) 2014 GNS3 Technologies 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 3 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, see <http://www.gnu.org/licenses/>.

"""
QEMU VM management (creates command line, processes, files etc.) in
order to run a QEMU VM.
"""

import sys
import os
import re
import math
import shutil
import shlex
import asyncio
import socket
import gns3server
import subprocess

from gns3server.utils import parse_version
from .qemu_error import QemuError
from ..adapters.ethernet_adapter import EthernetAdapter
from ..nios.nio_udp import NIOUDP
from ..nios.nio_tap import NIOTAP
from ..base_node import BaseNode
from ...schemas.qemu import QEMU_OBJECT_SCHEMA, QEMU_PLATFORMS
from ...utils.asyncio import monitor_process
from ...utils.images import md5sum
from .qcow2 import Qcow2, Qcow2Error
from ...utils import macaddress_to_int, int_to_macaddress


import logging
log = logging.getLogger(__name__)


class QemuVM(BaseNode):
    module_name = 'qemu'

    """
    QEMU VM implementation.

    :param name: Qemu VM name
    :param node_id: Node identifier
    :param project: Project instance
    :param manager: Manager instance
    :param console: TCP console port
    :param qemu_path: path to the QEMU binary
    :param platform: Platform to emulate
    :param console: TCP console port
    """

    def __init__(self, name, node_id, project, manager, linked_clone=True, qemu_path=None, console=None, console_type="telnet", platform=None):

        super().__init__(name, node_id, project, manager, console=console, console_type=console_type, wrap_console=True)
        server_config = manager.config.get_section_config("Server")
        self._host = server_config.get("host", "127.0.0.1")
        self._monitor_host = server_config.get("monitor_host", "127.0.0.1")
        self._process = None
        self._cpulimit_process = None
        self._monitor = None
        self._stdout_file = ""
        self._execute_lock = asyncio.Lock()
        self._local_udp_tunnels = {}

        # QEMU VM settings
        if qemu_path:
            try:
                self.qemu_path = qemu_path
            except QemuError as e:
                # If the binary is not found for topologies 1.4 and later
                # search via the platform otherwise use the binary name
                if platform:
                    self.platform = platform
                else:
                    self.qemu_path = os.path.basename(qemu_path)
        else:
            self.platform = platform

        self._hda_disk_image = ""
        self._hdb_disk_image = ""
        self._hdc_disk_image = ""
        self._hdd_disk_image = ""
        self._hda_disk_interface = "ide"
        self._hdb_disk_interface = "ide"
        self._hdc_disk_interface = "ide"
        self._hdd_disk_interface = "ide"
        self._cdrom_image = ""
        self._bios_image = ""
        self._boot_priority = "c"
        self._mac_address = ""
        self._options = ""
        self._ram = 256
        self._cpus = 1
        self._ethernet_adapters = []
        self._adapter_type = "e1000"
        self._initrd = ""
        self._kernel_image = ""
        self._kernel_command_line = ""
        self._legacy_networking = False
        self._acpi_shutdown = False
        self._cpu_throttling = 0  # means no CPU throttling
        self._process_priority = "low"

        self.mac_address = ""  # this will generate a MAC address
        self.adapters = 1  # creates 1 adapter by default
        log.info('QEMU VM "{name}" [{id}] has been created'.format(name=self._name, id=self._id))

    @property
    def monitor(self):
        """
        Returns the TCP monitor port.

        :returns: monitor port (integer)
        """

        return self._monitor

    @property
    def qemu_path(self):
        """
        Returns the QEMU binary path for this QEMU VM.

        :returns: QEMU path
        """

        return self._qemu_path

    @qemu_path.setter
    def qemu_path(self, qemu_path):
        """
        Sets the QEMU binary path this QEMU VM.

        :param qemu_path: QEMU path
        """

        if qemu_path and os.pathsep not in qemu_path:
            if sys.platform.startswith("win") and ".exe" not in qemu_path.lower():
                qemu_path += "w.exe"
            new_qemu_path = shutil.which(qemu_path, path=os.pathsep.join(self._manager.paths_list()))
            if new_qemu_path is None:
                raise QemuError("QEMU binary path {} is not found in the path".format(qemu_path))
            qemu_path = new_qemu_path

        self._check_qemu_path(qemu_path)
        self._qemu_path = qemu_path
        self._platform = os.path.basename(qemu_path)
        if self._platform == "qemu-kvm":
            self._platform = "x86_64"
        else:
            qemu_bin = os.path.basename(qemu_path)
            qemu_bin = re.sub(r'(w)?\.(exe|EXE)$', '', qemu_bin)
            # Old version of GNS3 provide a binary named qemu.exe
            if qemu_bin == "qemu":
                self._platform = "i386"
            else:
                self._platform = re.sub(r'^qemu-system-(.*)$', r'\1', qemu_bin, re.IGNORECASE)
        if self._platform.split(".")[0] not in QEMU_PLATFORMS:
            raise QemuError("Platform {} is unknown".format(self._platform))
        log.info('QEMU VM "{name}" [{id}] has set the QEMU path to {qemu_path}'.format(name=self._name,
                                                                                       id=self._id,
                                                                                       qemu_path=qemu_path))

    def _check_qemu_path(self, qemu_path):
        if qemu_path is None:
            raise QemuError("QEMU binary path is not set")
        if not os.path.exists(qemu_path):
            raise QemuError("QEMU binary '{}' is not accessible".format(qemu_path))
        if not os.access(qemu_path, os.X_OK):
            raise QemuError("QEMU binary '{}' is not executable".format(qemu_path))

    @property
    def platform(self):
        """
        Return the current platform
        """
        return self._platform

    @platform.setter
    def platform(self, platform):
        self._platform = platform
        if sys.platform.startswith("win"):
            self.qemu_path = "qemu-system-{}w.exe".format(platform)
        else:
            self.qemu_path = "qemu-system-{}".format(platform)

    def _disk_setter(self, variable, value):
        """
        Use by disk image setter for checking and apply modifications

        :param variable: Variable name in the class
        :param value: New disk value
        """
        value = self.manager.get_abs_image_path(value)
        if not self.linked_clone:
            for node in self.manager.nodes:
                if node != self and getattr(node, variable) == value:
                    raise QemuError("Sorry a node without the linked base setting enabled can only be used once on your server. {} is already used by {}".format(value, node.name))
        setattr(self, "_" + variable, value)
        log.info('QEMU VM "{name}" [{id}] has set the QEMU {variable} path to {disk_image}'.format(name=self._name,
                                                                                                   variable=variable,
                                                                                                   id=self._id,
                                                                                                   disk_image=value))

    @property
    def hda_disk_image(self):
        """
        Returns the hda disk image path for this QEMU VM.

        :returns: QEMU hda disk image path
        """

        return self._hda_disk_image

    @hda_disk_image.setter
    def hda_disk_image(self, hda_disk_image):
        """
        Sets the hda disk image for this QEMU VM.

        :param hda_disk_image: QEMU hda disk image path
        """
        self._disk_setter("hda_disk_image", hda_disk_image)

    @property
    def hdb_disk_image(self):
        """
        Returns the hdb disk image path for this QEMU VM.

        :returns: QEMU hdb disk image path
        """

        return self._hdb_disk_image

    @hdb_disk_image.setter
    def hdb_disk_image(self, hdb_disk_image):
        """
        Sets the hdb disk image for this QEMU VM.

        :param hdb_disk_image: QEMU hdb disk image path
        """

        self._disk_setter("hdb_disk_image", hdb_disk_image)

    @property
    def hdc_disk_image(self):
        """
        Returns the hdc disk image path for this QEMU VM.

        :returns: QEMU hdc disk image path
        """

        return self._hdc_disk_image

    @hdc_disk_image.setter
    def hdc_disk_image(self, hdc_disk_image):
        """
        Sets the hdc disk image for this QEMU VM.

        :param hdc_disk_image: QEMU hdc disk image path
        """

        self._disk_setter("hdc_disk_image", hdc_disk_image)

    @property
    def hdd_disk_image(self):
        """
        Returns the hdd disk image path for this QEMU VM.

        :returns: QEMU hdd disk image path
        """

        return self._hdd_disk_image

    @hdd_disk_image.setter
    def hdd_disk_image(self, hdd_disk_image):
        """
        Sets the hdd disk image for this QEMU VM.

        :param hdd_disk_image: QEMU hdd disk image path
        """

        self._disk_setter("hdd_disk_image", hdd_disk_image)

    @property
    def hda_disk_interface(self):
        """
        Returns the hda disk interface this QEMU VM.

        :returns: QEMU hda disk interface
        """

        return self._hda_disk_interface

    @hda_disk_interface.setter
    def hda_disk_interface(self, hda_disk_interface):
        """
        Sets the hda disk interface for this QEMU VM.

        :param hda_disk_interface: QEMU hda disk interface
        """

        self._hda_disk_interface = hda_disk_interface
        log.info('QEMU VM "{name}" [{id}] has set the QEMU hda disk interface to {interface}'.format(name=self._name,
                                                                                                     id=self._id,
                                                                                                     interface=self._hda_disk_interface))

    @property
    def hdb_disk_interface(self):
        """
        Returns the hdb disk interface this QEMU VM.

        :returns: QEMU hdb disk interface
        """

        return self._hdb_disk_interface

    @hdb_disk_interface.setter
    def hdb_disk_interface(self, hdb_disk_interface):
        """
        Sets the hda disk interface for this QEMU VM.

        :param hdb_disk_interface: QEMU hdb disk interface
        """

        self._hdb_disk_interface = hdb_disk_interface
        log.info('QEMU VM "{name}" [{id}] has set the QEMU hdb disk interface to {interface}'.format(name=self._name,
                                                                                                     id=self._id,
                                                                                                     interface=self._hdb_disk_interface))

    @property
    def hdc_disk_interface(self):
        """
        Returns the hdc disk interface this QEMU VM.

        :returns: QEMU hdc disk interface
        """

        return self._hdc_disk_interface

    @hdc_disk_interface.setter
    def hdc_disk_interface(self, hdc_disk_interface):
        """
        Sets the hdc disk interface for this QEMU VM.

        :param hdc_disk_interface: QEMU hdc disk interface
        """

        self._hdc_disk_interface = hdc_disk_interface
        log.info('QEMU VM "{name}" [{id}] has set the QEMU hdc disk interface to {interface}'.format(name=self._name,
                                                                                                     id=self._id,
                                                                                                     interface=self._hdc_disk_interface))

    @property
    def hdd_disk_interface(self):
        """
        Returns the hda disk interface this QEMU VM.

        :returns: QEMU hda disk interface
        """

        return self._hdd_disk_interface

    @hdd_disk_interface.setter
    def hdd_disk_interface(self, hdd_disk_interface):
        """
        Sets the hdd disk interface for this QEMU VM.

        :param hdd_disk_interface: QEMU hdd disk interface
        """

        self._hdd_disk_interface = hdd_disk_interface
        log.info('QEMU VM "{name}" [{id}] has set the QEMU hdd disk interface to {interface}'.format(name=self._name,
                                                                                                     id=self._id,
                                                                                                     interface=self._hdd_disk_interface))

    @property
    def cdrom_image(self):
        """
        Returns the cdrom image path for this QEMU VM.

        :returns: QEMU cdrom image path
        """

        return self._cdrom_image

    @cdrom_image.setter
    def cdrom_image(self, cdrom_image):
        """
        Sets the cdrom image for this QEMU VM.

        :param cdrom_image: QEMU cdrom image path
        """
        self._cdrom_image = self.manager.get_abs_image_path(cdrom_image)
        log.info('QEMU VM "{name}" [{id}] has set the QEMU cdrom image path to {cdrom_image}'.format(name=self._name,
                                                                                                     id=self._id,
                                                                                                     cdrom_image=self._cdrom_image))

    @property
    def bios_image(self):
        """
        Returns the bios image path for this QEMU VM.

        :returns: QEMU bios image path
        """

        return self._bios_image

    @bios_image.setter
    def bios_image(self, bios_image):
        """
        Sets the bios image for this QEMU VM.

        :param bios_image: QEMU bios image path
        """
        self._bios_image = self.manager.get_abs_image_path(bios_image)
        log.info('QEMU VM "{name}" [{id}] has set the QEMU bios image path to {bios_image}'.format(name=self._name,
                                                                                                   id=self._id,
                                                                                                   bios_image=self._bios_image))

    @property
    def boot_priority(self):
        """
        Returns the boot priority for this QEMU VM.

        :returns: QEMU boot priority
        """

        return self._boot_priority

    @boot_priority.setter
    def boot_priority(self, boot_priority):
        """
        Sets the boot priority for this QEMU VM.

        :param boot_priority: QEMU boot priority
        """

        self._boot_priority = boot_priority
        log.info('QEMU VM "{name}" [{id}] has set the boot priority to {boot_priority}'.format(name=self._name,
                                                                                               id=self._id,
                                                                                               boot_priority=self._boot_priority))

    @property
    def adapters(self):
        """
        Returns the number of Ethernet adapters for this QEMU VM.

        :returns: number of adapters
        """

        return len(self._ethernet_adapters)

    @adapters.setter
    def adapters(self, adapters):
        """
        Sets the number of Ethernet adapters for this QEMU VM.

        :param adapters: number of adapters
        """

        self._ethernet_adapters.clear()
        for adapter_number in range(0, adapters):
            self._ethernet_adapters.append(EthernetAdapter())

        log.info('QEMU VM "{name}" [{id}]: number of Ethernet adapters changed to {adapters}'.format(name=self._name,
                                                                                                     id=self._id,
                                                                                                     adapters=adapters))

    @property
    def adapter_type(self):
        """
        Returns the adapter type for this QEMU VM.

        :returns: adapter type (string)
        """

        return self._adapter_type

    @adapter_type.setter
    def adapter_type(self, adapter_type):
        """
        Sets the adapter type for this QEMU VM.

        :param adapter_type: adapter type (string)
        """

        self._adapter_type = adapter_type

        log.info('QEMU VM "{name}" [{id}]: adapter type changed to {adapter_type}'.format(name=self._name,
                                                                                          id=self._id,
                                                                                          adapter_type=adapter_type))

    @property
    def mac_address(self):
        """
        Returns the MAC address for this QEMU VM.

        :returns: adapter type (string)
        """

        return self._mac_address

    @mac_address.setter
    def mac_address(self, mac_address):
        """
        Sets the MAC address for this QEMU VM.

        :param mac_address: MAC address
        """

        if not mac_address:
            # use the node UUID to generate a random MAC address
            self._mac_address = "00:%s:%s:%s:%s:00" % (self.project.id[-4:-2], self.project.id[-2:], self.id[-4:-2], self.id[-2:])
        else:
            self._mac_address = mac_address

        log.info('QEMU VM "{name}" [{id}]: MAC address changed to {mac_addr}'.format(name=self._name,
                                                                                     id=self._id,
                                                                                     mac_addr=mac_address))

    @property
    def legacy_networking(self):
        """
        Returns either QEMU legacy networking commands are used.

        :returns: boolean
        """

        return self._legacy_networking

    @legacy_networking.setter
    def legacy_networking(self, legacy_networking):
        """
        Sets either QEMU legacy networking commands are used.

        :param legacy_networking: boolean
        """

        if legacy_networking:
            log.info('QEMU VM "{name}" [{id}] has enabled legacy networking'.format(name=self._name, id=self._id))
        else:
            log.info('QEMU VM "{name}" [{id}] has disabled legacy networking'.format(name=self._name, id=self._id))
        self._legacy_networking = legacy_networking

    @property
    def acpi_shutdown(self):
        """
        Returns either this QEMU VM can be ACPI shutdown.

        :returns: boolean
        """

        return self._acpi_shutdown

    @acpi_shutdown.setter
    def acpi_shutdown(self, acpi_shutdown):
        """
        Sets either this QEMU VM can be ACPI shutdown.

        :param acpi_shutdown: boolean
        """

        if acpi_shutdown:
            log.info('QEMU VM "{name}" [{id}] has enabled ACPI shutdown'.format(name=self._name, id=self._id))
        else:
            log.info('QEMU VM "{name}" [{id}] has disabled ACPI shutdown'.format(name=self._name, id=self._id))
        self._acpi_shutdown = acpi_shutdown

    @property
    def cpu_throttling(self):
        """
        Returns the percentage of CPU allowed.

        :returns: integer
        """

        return self._cpu_throttling

    @cpu_throttling.setter
    def cpu_throttling(self, cpu_throttling):
        """
        Sets the percentage of CPU allowed.

        :param cpu_throttling: integer
        """

        log.info('QEMU VM "{name}" [{id}] has set the percentage of CPU allowed to {cpu}'.format(name=self._name,
                                                                                                 id=self._id,
                                                                                                 cpu=cpu_throttling))
        self._cpu_throttling = cpu_throttling
        self._stop_cpulimit()
        if cpu_throttling:
            self._set_cpu_throttling()

    @property
    def process_priority(self):
        """
        Returns the process priority.

        :returns: string
        """

        return self._process_priority

    @process_priority.setter
    def process_priority(self, process_priority):
        """
        Sets the process priority.

        :param process_priority: string
        """

        log.info('QEMU VM "{name}" [{id}] has set the process priority to {priority}'.format(name=self._name,
                                                                                             id=self._id,
                                                                                             priority=process_priority))
        self._process_priority = process_priority

    @property
    def ram(self):
        """
        Returns the RAM amount for this QEMU VM.

        :returns: RAM amount in MB
        """

        return self._ram

    @ram.setter
    def ram(self, ram):
        """
        Sets the amount of RAM for this QEMU VM.

        :param ram: RAM amount in MB
        """

        log.info('QEMU VM "{name}" [{id}] has set the RAM to {ram}'.format(name=self._name, id=self._id, ram=ram))
        self._ram = ram

    @property
    def cpus(self):
        """
        Returns the number of vCPUs this QEMU VM.

        :returns: number of vCPUs.
        """

        return self._cpus

    @cpus.setter
    def cpus(self, cpus):
        """
        Sets the number of vCPUs this QEMU VM.

        :param cpus: number of vCPUs.
        """

        log.info('QEMU VM "{name}" [{id}] has set the number of vCPUs to {cpus}'.format(name=self._name, id=self._id, cpus=cpus))
        self._cpus = cpus

    @property
    def options(self):
        """
        Returns the options for this QEMU VM.

        :returns: QEMU options
        """

        return self._options

    @options.setter
    def options(self, options):
        """
        Sets the options for this QEMU VM.

        :param options: QEMU options
        """

        log.info('QEMU VM "{name}" [{id}] has set the QEMU options to {options}'.format(name=self._name,
                                                                                        id=self._id,
                                                                                        options=options))

        if not sys.platform.startswith("linux"):
            if "-no-kvm" in options:
                options = options.replace("-no-kvm", "")
            if "-enable-kvm" in options:
                options = options.replace("-enable-kvm", "")
        elif "-icount" in options and ("-no-kvm" not in options):
            # automatically add the -no-kvm option if -icount is detected
            # to help with the migration of ASA VMs created before version 1.4
            options = "-no-kvm " + options
        self._options = options.strip()

    @property
    def initrd(self):
        """
        Returns the initrd path for this QEMU VM.

        :returns: QEMU initrd path
        """

        return self._initrd

    @initrd.setter
    def initrd(self, initrd):
        """
        Sets the initrd path for this QEMU VM.

        :param initrd: QEMU initrd path
        """

        initrd = self.manager.get_abs_image_path(initrd)

        log.info('QEMU VM "{name}" [{id}] has set the QEMU initrd path to {initrd}'.format(name=self._name,
                                                                                           id=self._id,
                                                                                           initrd=initrd))
        if "asa" in initrd:
            self.project.emit("log.warning", {"message": "Warning ASA 8 is not supported by GNS3 and Cisco, you need to use ASAv. Depending of your hardware and OS this could not work or you could be limited to one instance. If ASA 8 is not booting their is no GNS3 solution, you need to upgrade to ASAv."})
        self._initrd = initrd

    @property
    def kernel_image(self):
        """
        Returns the kernel image path for this QEMU VM.

        :returns: QEMU kernel image path
        """

        return self._kernel_image

    @kernel_image.setter
    def kernel_image(self, kernel_image):
        """
        Sets the kernel image path for this QEMU VM.

        :param kernel_image: QEMU kernel image path
        """

        kernel_image = self.manager.get_abs_image_path(kernel_image)
        log.info('QEMU VM "{name}" [{id}] has set the QEMU kernel image path to {kernel_image}'.format(name=self._name,
                                                                                                       id=self._id,
                                                                                                       kernel_image=kernel_image))
        self._kernel_image = kernel_image

    @property
    def kernel_command_line(self):
        """
        Returns the kernel command line for this QEMU VM.

        :returns: QEMU kernel command line
        """

        return self._kernel_command_line

    @kernel_command_line.setter
    def kernel_command_line(self, kernel_command_line):
        """
        Sets the kernel command line for this QEMU VM.

        :param kernel_command_line: QEMU kernel command line
        """

        log.info('QEMU VM "{name}" [{id}] has set the QEMU kernel command line to {kernel_command_line}'.format(name=self._name,
                                                                                                                id=self._id,
                                                                                                                kernel_command_line=kernel_command_line))
        self._kernel_command_line = kernel_command_line

    @asyncio.coroutine
    def _set_process_priority(self):
        """
        Changes the process priority
        """

        if self._process_priority == "normal":
            return

        if sys.platform.startswith("win"):
            try:
                import win32api
                import win32con
                import win32process
            except ImportError:
                log.error("pywin32 must be installed to change the priority class for QEMU VM {}".format(self._name))
            else:
                log.info("Setting QEMU VM {} priority class to {}".format(self._name, self._process_priority))
                handle = win32api.OpenProcess(win32con.PROCESS_ALL_ACCESS, 0, self._process.pid)
                if self._process_priority == "realtime":
                    priority = win32process.REALTIME_PRIORITY_CLASS
                elif self._process_priority == "very high":
                    priority = win32process.HIGH_PRIORITY_CLASS
                elif self._process_priority == "high":
                    priority = win32process.ABOVE_NORMAL_PRIORITY_CLASS
                elif self._process_priority == "low":
                    priority = win32process.BELOW_NORMAL_PRIORITY_CLASS
                elif self._process_priority == "very low":
                    priority = win32process.IDLE_PRIORITY_CLASS
                else:
                    priority = win32process.NORMAL_PRIORITY_CLASS
                try:
                    win32process.SetPriorityClass(handle, priority)
                except win32process.error as e:
                    log.error('Could not change process priority for QEMU VM "{}": {}'.format(self._name, e))
        else:
            if self._process_priority == "realtime":
                priority = -20
            elif self._process_priority == "very high":
                priority = -15
            elif self._process_priority == "high":
                priority = -5
            elif self._process_priority == "low":
                priority = 5
            elif self._process_priority == "very low":
                priority = 19
            else:
                priority = 0
            try:
                process = yield from asyncio.create_subprocess_exec('renice', '-n', str(priority), '-p', str(self._process.pid))
                yield from process.wait()
            except (OSError, subprocess.SubprocessError) as e:
                log.error('Could not change process priority for QEMU VM "{}": {}'.format(self._name, e))

    def _stop_cpulimit(self):
        """
        Stops the cpulimit process.
        """

        if self._cpulimit_process and self._cpulimit_process.returncode is None:
            self._cpulimit_process.kill()
            try:
                self._process.wait(3)
            except subprocess.TimeoutExpired:
                log.error("Could not kill cpulimit process {}".format(self._cpulimit_process.pid))

    def _set_cpu_throttling(self):
        """
        Limits the CPU usage for current QEMU process.
        """

        if not self.is_running():
            return

        try:
            if sys.platform.startswith("win") and hasattr(sys, "frozen"):
                cpulimit_exec = os.path.join(os.path.dirname(os.path.abspath(sys.executable)), "cpulimit", "cpulimit.exe")
            else:
                cpulimit_exec = "cpulimit"
            subprocess.Popen([cpulimit_exec, "--lazy", "--pid={}".format(self._process.pid), "--limit={}".format(self._cpu_throttling)], cwd=self.working_dir)
            log.info("CPU throttled to {}%".format(self._cpu_throttling))
        except FileNotFoundError:
            raise QemuError("cpulimit could not be found, please install it or deactivate CPU throttling")
        except (OSError, subprocess.SubprocessError) as e:
            raise QemuError("Could not throttle CPU: {}".format(e))

    @asyncio.coroutine
    def start(self):
        """
        Starts this QEMU VM.
        """

        with (yield from self._execute_lock):
            if self.is_running():
                # resume the VM if it is paused
                yield from self.resume()
                return

            if self._manager.config.get_section_config("Qemu").getboolean("monitor", True):
                try:
                    info = socket.getaddrinfo(self._monitor_host, 0, socket.AF_UNSPEC, socket.SOCK_STREAM, 0, socket.AI_PASSIVE)
                    if not info:
                        raise QemuError("getaddrinfo returns an empty list on {}".format(self._monitor_host))
                    for res in info:
                        af, socktype, proto, _, sa = res
                        # let the OS find an unused port for the Qemu monitor
                        with socket.socket(af, socktype, proto) as sock:
                            sock.bind(sa)
                            self._monitor = sock.getsockname()[1]
                except OSError as e:
                    raise QemuError("Could not find free port for the Qemu monitor: {}".format(e))

            # check if there is enough RAM to run
            self.check_available_ram(self.ram)

            command = yield from self._build_command()
            command_string = " ".join(shlex.quote(s) for s in command)
            try:
                log.info("Starting QEMU with: {}".format(command_string))
                self._stdout_file = os.path.join(self.working_dir, "qemu.log")
                log.info("logging to {}".format(self._stdout_file))
                with open(self._stdout_file, "w", encoding="utf-8") as fd:
                    fd.write("Start QEMU with {}\n\nExecution log:\n".format(command_string))
                    self.command_line = ' '.join(command)
                    self._process = yield from asyncio.create_subprocess_exec(*command,
                                                                              stdout=fd,
                                                                              stderr=subprocess.STDOUT,
                                                                              cwd=self.working_dir)

                if self.use_ubridge:
                    yield from self._start_ubridge()
                    for adapter_number, adapter in enumerate(self._ethernet_adapters):
                        nio = adapter.get_nio(0)
                        if nio:
                            yield from self._add_ubridge_udp_connection("QEMU-{}-{}".format(self._id, adapter_number),
                                                                        self._local_udp_tunnels[adapter_number][1],
                                                                        nio)

                log.info('QEMU VM "{}" started PID={}'.format(self._name, self._process.pid))
                self.status = "started"
                monitor_process(self._process, self._termination_callback)
            except (OSError, subprocess.SubprocessError, UnicodeEncodeError) as e:
                stdout = self.read_stdout()
                log.error("Could not start QEMU {}: {}\n{}".format(self.qemu_path, e, stdout))
                raise QemuError("Could not start QEMU {}: {}\n{}".format(self.qemu_path, e, stdout))

            yield from self._set_process_priority()
            if self._cpu_throttling:
                self._set_cpu_throttling()

            if "-enable-kvm" in command_string:
                self._hw_virtualization = True
        try:
            yield from self.start_wrap_console()
        except OSError as e:
            raise QemuError("Could not start QEMU console {}\n".format(e))

    @asyncio.coroutine
    def _termination_callback(self, returncode):
        """
        Called when the process has stopped.

        :param returncode: Process returncode
        """

        if self.started:
            log.info("QEMU process has stopped, return code: %d", returncode)
            yield from self.stop()
            # A return code of 1 seem fine on Windows
            if returncode != 0 and (returncode != 1 or not sys.platform.startswith("win")):
                self.project.emit("log.error", {"message": "QEMU process has stopped, return code: {}\n{}".format(returncode, self.read_stdout())})

    @asyncio.coroutine
    def stop(self):
        """
        Stops this QEMU VM.
        """

        yield from self._stop_ubridge()
        with (yield from self._execute_lock):
            # stop the QEMU process
            self._hw_virtualization = False
            if self.is_running():
                log.info('Stopping QEMU VM "{}" PID={}'.format(self._name, self._process.pid))
                try:
                    if self.acpi_shutdown:
                        yield from self._control_vm("system_powerdown")
                        yield from gns3server.utils.asyncio.wait_for_process_termination(self._process, timeout=30)
                    else:
                        self._process.terminate()
                        yield from gns3server.utils.asyncio.wait_for_process_termination(self._process, timeout=3)
                except ProcessLookupError:
                    pass
                except asyncio.TimeoutError:
                    if self._process:
                        try:
                            self._process.kill()
                        except ProcessLookupError:
                            pass
                        if self._process.returncode is None:
                            log.warn('QEMU VM "{}" PID={} is still running'.format(self._name, self._process.pid))
            self._process = None
            self._stop_cpulimit()
            yield from super().stop()

    @asyncio.coroutine
    def _control_vm(self, command, expected=None):
        """
        Executes a command with QEMU monitor when this VM is running.

        :param command: QEMU monitor command (e.g. info status, stop etc.)
        :param expected: An array of expected strings

        :returns: result of the command (matched object or None)
        """

        result = None
        if self.is_running() and self._monitor:
            log.debug("Execute QEMU monitor command: {}".format(command))
            try:
                log.info("Connecting to Qemu monitor on {}:{}".format(self._monitor_host, self._monitor))
                reader, writer = yield from asyncio.open_connection(self._monitor_host, self._monitor)
            except OSError as e:
                log.warn("Could not connect to QEMU monitor: {}".format(e))
                return result
            try:
                writer.write(command.encode('ascii') + b"\n")
            except OSError as e:
                log.warn("Could not write to QEMU monitor: {}".format(e))
                writer.close()
                return result
            if expected:
                try:
                    while result is None:
                        line = yield from reader.readline()
                        if not line:
                            break
                        for expect in expected:
                            if expect in line:
                                result = line.decode("utf-8").strip()
                                break
                except EOFError as e:
                    log.warn("Could not read from QEMU monitor: {}".format(e))
            writer.close()
        return result

    @asyncio.coroutine
    def close(self):
        """
        Closes this QEMU VM.
        """

        if not (yield from super().close()):
            return False

        self.acpi_shutdown = False
        yield from self.stop()

        for adapter in self._ethernet_adapters:
            if adapter is not None:
                for nio in adapter.ports.values():
                    if nio and isinstance(nio, NIOUDP):
                        self.manager.port_manager.release_udp_port(nio.lport, self._project)

        for udp_tunnel in self._local_udp_tunnels.values():
            self.manager.port_manager.release_udp_port(udp_tunnel[0].lport, self._project)
            self.manager.port_manager.release_udp_port(udp_tunnel[1].lport, self._project)
        self._local_udp_tunnels = {}

    @asyncio.coroutine
    def _get_vm_status(self):
        """
        Returns this VM suspend status.

        Status are extracted from:
          https://github.com/qemu/qemu/blob/master/qapi-schema.json#L152

        :returns: status (string)
        """

        result = yield from self._control_vm("info status", [
            b"debug", b"inmigrate", b"internal-error", b"io-error",
            b"paused", b"postmigrate", b"prelaunch", b"finish-migrate",
            b"restore-vm", b"running", b"save-vm", b"shutdown", b"suspended",
            b"watchdog", b"guest-panicked"
        ])
        if result is None:
            return result
        status = result.rsplit(' ', 1)[1]
        if status == "running" or status == "prelaunch":
            self.status = "started"
        elif status == "suspended":
            self.status = "suspended"
        elif status == "shutdown":
            self.status = "stopped"
        return status

    @asyncio.coroutine
    def suspend(self):
        """
        Suspends this QEMU VM.
        """

        if self.is_running():
            vm_status = yield from self._get_vm_status()
            if vm_status is None:
                raise QemuError("Suspending a QEMU VM is not supported")
            elif vm_status == "running" or vm_status == "prelaunch":
                yield from self._control_vm("stop")
                self.status = "suspended"
                log.debug("QEMU VM has been suspended")
            else:
                log.info("QEMU VM is not running to be suspended, current status is {}".format(vm_status))

    @asyncio.coroutine
    def reload(self):
        """
        Reloads this QEMU VM.
        """

        yield from self._control_vm("system_reset")
        log.debug("QEMU VM has been reset")

    @asyncio.coroutine
    def resume(self):
        """
        Resumes this QEMU VM.
        """

        vm_status = yield from self._get_vm_status()
        if vm_status is None:
            raise QemuError("Resuming a QEMU VM is not supported")
        elif vm_status == "paused":
            yield from self._control_vm("cont")
            log.debug("QEMU VM has been resumed")
        else:
            log.info("QEMU VM is not paused to be resumed, current status is {}".format(vm_status))

    @asyncio.coroutine
    def adapter_add_nio_binding(self, adapter_number, nio):
        """
        Adds a port NIO binding.

        :param adapter_number: adapter number
        :param nio: NIO instance to add to the adapter
        """

        try:
            adapter = self._ethernet_adapters[adapter_number]
        except IndexError:
            raise QemuError('Adapter {adapter_number} does not exist on QEMU VM "{name}"'.format(name=self._name,
                                                                                                 adapter_number=adapter_number))

        if self.ubridge:
            try:
                yield from self._add_ubridge_udp_connection("QEMU-{}-{}".format(self._id, adapter_number),
                                                            self._local_udp_tunnels[adapter_number][1],
                                                            nio)
            except IndexError:
                raise QemuError('Adapter {adapter_number} does not exist on QEMU VM "{name}"'.format(name=self._name,
                                                                                                     adapter_number=adapter_number))
        elif self.is_running():
            raise QemuError("Sorry, adding a link to a started Qemu VM is not supported without using uBridge.")

        adapter.add_nio(0, nio)
        log.info('QEMU VM "{name}" [{id}]: {nio} added to adapter {adapter_number}'.format(name=self._name,
                                                                                           id=self._id,
                                                                                           nio=nio,
                                                                                           adapter_number=adapter_number))

    @asyncio.coroutine
    def adapter_remove_nio_binding(self, adapter_number):
        """
        Removes a port NIO binding.

        :param adapter_number: adapter number

        :returns: NIO instance
        """

        try:
            adapter = self._ethernet_adapters[adapter_number]
        except IndexError:
            raise QemuError('Adapter {adapter_number} does not exist on QEMU VM "{name}"'.format(name=self._name,
                                                                                                 adapter_number=adapter_number))

        if self.ubridge:
            yield from self._ubridge_send("bridge delete {name}".format(name="QEMU-{}-{}".format(self._id, adapter_number)))
        elif self.is_running():
            raise QemuError("Sorry, removing a link to a started Qemu VM is not supported without using uBridge.")

        nio = adapter.get_nio(0)
        if isinstance(nio, NIOUDP):
            self.manager.port_manager.release_udp_port(nio.lport, self._project)
        adapter.remove_nio(0)

        log.info('QEMU VM "{name}" [{id}]: {nio} removed from adapter {adapter_number}'.format(name=self._name,
                                                                                               id=self._id,
                                                                                               nio=nio,
                                                                                               adapter_number=adapter_number))
        return nio

    @asyncio.coroutine
    def start_capture(self, adapter_number, output_file):
        """
        Starts a packet capture.

        :param adapter_number: adapter number
        :param output_file: PCAP destination file for the capture
        """

        try:
            adapter = self._ethernet_adapters[adapter_number]
        except IndexError:
            raise QemuError('Adapter {adapter_number} does not exist on QEMU VM "{name}"'.format(name=self._name,
                                                                                                 adapter_number=adapter_number))

        if not self.use_ubridge:
            raise QemuError("uBridge must be enabled in order to start packet capture")

        nio = adapter.get_nio(0)

        if not nio:
            raise QemuError("Adapter {} is not connected".format(adapter_number))

        if nio.capturing:
            raise QemuError("Packet capture is already activated on adapter {adapter_number}".format(adapter_number=adapter_number))

        nio.startPacketCapture(output_file)

        if self.ubridge:
            yield from self._ubridge_send('bridge start_capture {name} "{output_file}"'.format(name="QEMU-{}-{}".format(self._id, adapter_number),
                                                                                               output_file=output_file))

        log.info("QEMU VM '{name}' [{id}]: starting packet capture on adapter {adapter_number}".format(name=self.name,
                                                                                                       id=self.id,
                                                                                                       adapter_number=adapter_number))

    def stop_capture(self, adapter_number):
        """
        Stops a packet capture.

        :param adapter_number: adapter number
        """

        try:
            adapter = self._ethernet_adapters[adapter_number]
        except IndexError:
            raise QemuError('Adapter {adapter_number} does not exist on QEMU VM "{name}"'.format(name=self._name,
                                                                                                 adapter_number=adapter_number))
        nio = adapter.get_nio(0)

        if not nio:
            raise QemuError("Adapter {} is not connected".format(adapter_number))

        nio.stopPacketCapture()

        if self.ubridge:
            yield from self._ubridge_send('bridge stop_capture {name}'.format(name="QEMU-{}-{}".format(self._id, adapter_number)))

        log.info("QEMU VM '{name}' [{id}]: stopping packet capture on adapter {adapter_number}".format(name=self.name,
                                                                                                       id=self.id,
                                                                                                       adapter_number=adapter_number))

    @property
    def started(self):
        """
        Returns either this QEMU VM has been started or not.

        :returns: boolean
        """

        return self.status == "started"

    def read_stdout(self):
        """
        Reads the standard output of the QEMU process.
        Only use when the process has been stopped or has crashed.
        """

        output = ""
        if self._stdout_file:
            try:
                with open(self._stdout_file, "rb") as file:
                    output = file.read().decode("utf-8", errors="replace")
            except OSError as e:
                log.warn("Could not read {}: {}".format(self._stdout_file, e))
        return output

    def is_running(self):
        """
        Checks if the QEMU process is running

        :returns: True or False
        """

        if self._process:
            if self._process.returncode is None:
                return True
            else:
                self._process = None
        return False

    def command(self):
        """
        Returns the QEMU command line.

        :returns: QEMU command line (string)
        """

        return " ".join(self._build_command())

    def _serial_options(self):

        if self._console:
            return ["-serial", "telnet:127.0.0.1:{},server,nowait".format(self._internal_console_port)]
        else:
            return []

    def _vnc_options(self):

        if self._console:
            vnc_port = self._console - 5900  # subtract by 5900 to get the display number
            return ["-vnc", "{}:{}".format(self._manager.port_manager.console_host, vnc_port)]
        else:
            return []

    def _spice_options(self):

        if self._console:
            return ["-spice",
                    "addr={},port={},disable-ticketing".format(self._manager.port_manager.console_host, self._console),
                    "-vga", "qxl"]
        else:
            return []

    def _monitor_options(self):

        if self._monitor:
            return ["-monitor", "tcp:{}:{},server,nowait".format(self._monitor_host, self._monitor)]
        else:
            return []

    def _get_qemu_img(self):
        """
        Search the qemu-img binary in the same binary of the qemu binary
        for avoiding version incompatibily.

        :returns: qemu-img path or raise an error
        """
        qemu_img_path = ""
        qemu_path_dir = os.path.dirname(self.qemu_path)
        try:
            for f in os.listdir(qemu_path_dir):
                if f.startswith("qemu-img"):
                    qemu_img_path = os.path.join(qemu_path_dir, f)
        except OSError as e:
            raise QemuError("Error while looking for qemu-img in {}: {}".format(qemu_path_dir, e))

        if not qemu_img_path:
            raise QemuError("Could not find qemu-img in {}".format(qemu_path_dir))

        return qemu_img_path

    @asyncio.coroutine
    def _disk_options(self):
        options = []
        qemu_img_path = self._get_qemu_img()

        drives = ["a", "b", "c", "d"]

        for disk_index, drive in enumerate(drives):
            disk_image = getattr(self, "_hd{}_disk_image".format(drive))
            interface = getattr(self, "hd{}_disk_interface".format(drive))

            if not disk_image:
                continue

            disk_name = "hd" + drive

            if not os.path.isfile(disk_image) or not os.path.exists(disk_image):
                if os.path.islink(disk_image):
                    raise QemuError("{} disk image '{}' linked to '{}' is not accessible".format(disk_name, disk_image, os.path.realpath(disk_image)))
                else:
                    raise QemuError("{} disk image '{}' is not accessible".format(disk_name, disk_image))
            if self.linked_clone:
                disk = os.path.join(self.working_dir, "{}_disk.qcow2".format(disk_name))
                if not os.path.exists(disk):
                    # create the disk
                    try:
                        process = yield from asyncio.create_subprocess_exec(qemu_img_path, "create", "-o",
                                                                            "backing_file={}".format(disk_image),
                                                                            "-f", "qcow2", disk)
                        retcode = yield from process.wait()
                        if retcode is not None and retcode != 0:
                            raise QemuError("Could not create {} disk image".format(disk_name))
                        log.info("{} returned with {}".format(qemu_img_path, retcode))
                    except (OSError, subprocess.SubprocessError) as e:
                        raise QemuError("Could not create {} disk image {}".format(disk_name, e))
                else:
                    # The disk exists we check if the clone work
                    try:
                        qcow2 = Qcow2(disk)
                        yield from qcow2.rebase(qemu_img_path, disk_image)
                    except (Qcow2Error, OSError) as e:
                        raise QemuError("Could not use qcow2 disk image {} for {} {}".format(disk_image, disk_name, e))

            else:
                disk = disk_image

            if interface == "sata":
                # special case, sata controller doesn't exist in Qemu
                options.extend(["-device", 'ahci,id=ahci{},bus=pci.{}'.format(disk_index, disk_index)])
                options.extend(["-drive", 'file={},if=none,id=drive-sata-disk{},index={},media=disk'.format(disk, disk_index, disk_index)])
                options.extend(["-device", 'ide-drive,drive=drive-sata-disk{},bus=ahci{}.0,id=drive-sata-disk{}'.format(disk_index, disk_index, disk_index)])
            else:
                options.extend(["-drive", 'file={},if={},index={},media=disk'.format(disk, interface, disk_index)])

        return options

    def _cdrom_option(self):

        options = []
        if self._cdrom_image:
            if not os.path.isfile(self._cdrom_image) or not os.path.exists(self._cdrom_image):
                if os.path.islink(self._cdrom_image):
                    raise QemuError("cdrom image '{}' linked to '{}' is not accessible".format(self._cdrom_image, os.path.realpath(self._cdrom_image)))
                else:
                    raise QemuError("cdrom image '{}' is not accessible".format(self._cdrom_image))
            if self._hdc_disk_image:
                raise QemuError("You cannot use a disk image on hdc disk and a CDROM image at the same time")
            options.extend(["-cdrom", self._cdrom_image])
        return options

    def _bios_option(self):

        options = []
        if self._bios_image:
            if not os.path.isfile(self._bios_image) or not os.path.exists(self._bios_image):
                if os.path.islink(self._bios_image):
                    raise QemuError("bios image '{}' linked to '{}' is not accessible".format(self._bios_image, os.path.realpath(self._bios_image)))
                else:
                    raise QemuError("bios image '{}' is not accessible".format(self._bios_image))
            options.extend(["-bios", self._bios_image])
        return options

    def _linux_boot_options(self):

        options = []
        if self._initrd:
            if not os.path.isfile(self._initrd) or not os.path.exists(self._initrd):
                if os.path.islink(self._initrd):
                    raise QemuError("initrd file '{}' linked to '{}' is not accessible".format(self._initrd, os.path.realpath(self._initrd)))
                else:
                    raise QemuError("initrd file '{}' is not accessible".format(self._initrd))
            options.extend(["-initrd", self._initrd])
        if self._kernel_image:
            if not os.path.isfile(self._kernel_image) or not os.path.exists(self._kernel_image):
                if os.path.islink(self._kernel_image):
                    raise QemuError("kernel image '{}' linked to '{}' is not accessible".format(self._kernel_image, os.path.realpath(self._kernel_image)))
                else:
                    raise QemuError("kernel image '{}' is not accessible".format(self._kernel_image))
            options.extend(["-kernel", self._kernel_image])
        if self._kernel_command_line:
            options.extend(["-append", self._kernel_command_line])

        return options

    @asyncio.coroutine
    def _network_options(self):

        network_options = []
        network_options.extend(["-net", "none"])  # we do not want any user networking back-end if no adapter is connected.

        patched_qemu = False
        if self._legacy_networking:
            version = yield from self.manager.get_qemu_version(self.qemu_path)
            if version and parse_version(version) < parse_version("1.1.0"):
                # this is a patched Qemu if version is below 1.1.0
                patched_qemu = True

        # Each 32 PCI device we need to add a PCI bridge with max 9 bridges
        pci_devices = 4 + len(self._ethernet_adapters)  # 4 PCI devices are use by default by qemu
        bridge_id = 0
        for bridge_id in range(1, math.floor(pci_devices / 32) + 1):
            network_options.extend(["-device", "i82801b11-bridge,id=dmi_pci_bridge{bridge_id}".format(bridge_id=bridge_id)])
            network_options.extend(["-device", "pci-bridge,id=pci-bridge{bridge_id},bus=dmi_pci_bridge{bridge_id},chassis_nr=0x1,addr=0x{bridge_id},shpc=off".format(bridge_id=bridge_id)])

        if bridge_id > 1:
            qemu_version = yield from self.manager.get_qemu_version(self.qemu_path)
            if qemu_version and parse_version(qemu_version) < parse_version("2.4.0"):
                raise QemuError("Qemu version 2.4 or later is required to run this VM with a large number of network adapters")

        pci_device_id = 4 + bridge_id  # Bridge consume PCI ports

        for adapter_number, adapter in enumerate(self._ethernet_adapters):
            mac = int_to_macaddress(macaddress_to_int(self._mac_address) + adapter_number)

            if self.use_ubridge:
                # use a local UDP tunnel to connect to uBridge instead
                if adapter_number not in self._local_udp_tunnels:
                    self._local_udp_tunnels[adapter_number] = self._create_local_udp_tunnel()
                nio = self._local_udp_tunnels[adapter_number][0]
            else:
                nio = adapter.get_nio(0)
            if self._legacy_networking:
                # legacy QEMU networking syntax (-net)
                if nio:
                    network_options.extend(["-net", "nic,vlan={},macaddr={},model={}".format(adapter_number, mac, self._adapter_type)])
                    if isinstance(nio, NIOUDP):
                        if patched_qemu:
                            # use patched Qemu syntax
                            network_options.extend(["-net", "udp,vlan={},name=gns3-{},sport={},dport={},daddr={}".format(adapter_number,
                                                                                                                         adapter_number,
                                                                                                                         nio.lport,
                                                                                                                         nio.rport,
                                                                                                                         nio.rhost)])
                        else:
                            # use UDP tunnel support added in Qemu 1.1.0
                            network_options.extend(["-net", "socket,vlan={},name=gns3-{},udp={}:{},localaddr={}:{}".format(adapter_number,
                                                                                                                           adapter_number,
                                                                                                                           nio.rhost,
                                                                                                                           nio.rport,
                                                                                                                           "127.0.0.1",
                                                                                                                           nio.lport)])
                    elif isinstance(nio, NIOTAP):
                        network_options.extend(["-net", "tap,name=gns3-{},ifname={}".format(adapter_number, nio.tap_device)])
                else:
                    network_options.extend(["-net", "nic,vlan={},macaddr={},model={}".format(adapter_number, mac, self._adapter_type)])

            else:
                # newer QEMU networking syntax
                device_string = "{},mac={}".format(self._adapter_type, mac)
                bridge_id = math.floor(pci_device_id / 32)
                if bridge_id > 0:
                    addr = pci_device_id % 32
                    device_string = "{},bus=pci-bridge{bridge_id},addr=0x{addr:02x}".format(device_string, bridge_id=bridge_id, addr=addr)
                pci_device_id += 1
                if nio:
                    network_options.extend(["-device", "{},netdev=gns3-{}".format(device_string, adapter_number)])
                    if isinstance(nio, NIOUDP):
                        network_options.extend(["-netdev", "socket,id=gns3-{},udp={}:{},localaddr={}:{}".format(adapter_number,
                                                                                                                nio.rhost,
                                                                                                                nio.rport,
                                                                                                                "127.0.0.1",
                                                                                                                nio.lport)])
                    elif isinstance(nio, NIOTAP):
                        network_options.extend(["-netdev", "tap,id=gns3-{},ifname={},script=no,downscript=no".format(adapter_number, nio.tap_device)])
                else:
                    network_options.extend(["-device", device_string])

        return network_options

    def _graphic(self):
        """
        Adds the correct graphic options depending of the OS
        """

        if sys.platform.startswith("win"):
            return []
        if len(os.environ.get("DISPLAY", "")) > 0:
            return []
        return ["-nographic"]

    def _run_with_kvm(self, qemu_path, options):
        """
        Check if we could run qemu with KVM

        :param qemu_path: Path to qemu
        :param options: String of qemu user options
        :returns: Boolean True if we need to enable KVM
        """

        if sys.platform.startswith("linux") and self.manager.config.get_section_config("Qemu").getboolean("enable_kvm", True) \
                and "-no-kvm" not in options:

            # Turn OFF kvm for non x86 architectures
            if os.path.basename(qemu_path) not in ["qemu-system-x86_64", "qemu-system-i386", "qemu-kvm"]:
                return False

            if not os.path.exists("/dev/kvm"):
                raise QemuError("KVM acceleration cannot be used (/dev/kvm doesn't exist). You can turn off KVM support in the gns3_server.conf by adding enable_kvm = false to the [Qemu] section.")
            return True
        return False

    @asyncio.coroutine
    def _build_command(self):
        """
        Command to start the QEMU process.
        (to be passed to subprocess.Popen())
        """

        additional_options = self._options.strip()
        command = [self.qemu_path]
        command.extend(["-name", self._name])
        command.extend(["-m", "{}M".format(self._ram)])
        command.extend(["-smp", "cpus={}".format(self._cpus)])
        if self._run_with_kvm(self.qemu_path, self._options):
            command.extend(["-enable-kvm"])
            version = yield from self.manager.get_qemu_version(self.qemu_path)
            # Issue on some combo Intel CPU + KVM + Qemu 2.4.0
            # https://github.com/GNS3/gns3-server/issues/685
            if version and parse_version(version) >= parse_version("2.4.0") and self.platform == "x86_64":
                command.extend(["-machine", "smm=off"])
        command.extend(["-boot", "order={}".format(self._boot_priority)])
        command.extend(self._bios_option())
        command.extend(self._cdrom_option())
        command.extend((yield from self._disk_options()))
        command.extend(self._linux_boot_options())
        if "-uuid" not in additional_options:
            command.extend(["-uuid", self._id])
        if self._console_type == "telnet":
            command.extend(self._serial_options())
        elif self._console_type == "vnc":
            command.extend(self._vnc_options())
        elif self._console_type == "spice":
            command.extend(self._spice_options())
        else:
            raise QemuError("Console type {} is unknown".format(self._console_type))
        command.extend(self._monitor_options())
        command.extend((yield from self._network_options()))
        command.extend(self._graphic())
        if additional_options:
            try:
                command.extend(shlex.split(additional_options))
            except ValueError as e:
                raise QemuError("Invalid additional options: {} error {}".format(additional_options, e))
        return command

    def __json__(self):
        answer = {
            "project_id": self.project.id,
            "node_id": self.id,
            "node_directory": self.working_dir
        }
        # Qemu has a long list of options. The JSON schema is the single source of information
        for field in QEMU_OBJECT_SCHEMA["required"]:
            if field not in answer:
                try:
                    answer[field] = getattr(self, field)
                except AttributeError:
                    pass
        answer["hda_disk_image"] = self.manager.get_relative_image_path(self._hda_disk_image)
        answer["hda_disk_image_md5sum"] = md5sum(self._hda_disk_image)
        answer["hdb_disk_image"] = self.manager.get_relative_image_path(self._hdb_disk_image)
        answer["hdb_disk_image_md5sum"] = md5sum(self._hdb_disk_image)
        answer["hdc_disk_image"] = self.manager.get_relative_image_path(self._hdc_disk_image)
        answer["hdc_disk_image_md5sum"] = md5sum(self._hdc_disk_image)
        answer["hdd_disk_image"] = self.manager.get_relative_image_path(self._hdd_disk_image)
        answer["hdd_disk_image_md5sum"] = md5sum(self._hdd_disk_image)
        answer["cdrom_image"] = self.manager.get_relative_image_path(self._cdrom_image)
        answer["cdrom_image_md5sum"] = md5sum(self._cdrom_image)
        answer["bios_image"] = self.manager.get_relative_image_path(self._bios_image)
        answer["bios_image_md5sum"] = md5sum(self._bios_image)
        answer["initrd"] = self.manager.get_relative_image_path(self._initrd)
        answer["initrd_md5sum"] = md5sum(self._initrd)

        answer["kernel_image"] = self.manager.get_relative_image_path(self._kernel_image)
        answer["kernel_image_md5sum"] = md5sum(self._kernel_image)

        return answer