xref: /openbmc/qemu/python/qemu/machine/machine.py (revision de799beb)
1"""
2QEMU machine module:
3
4The machine module primarily provides the QEMUMachine class,
5which provides facilities for managing the lifetime of a QEMU VM.
6"""
7
8# Copyright (C) 2015-2016 Red Hat Inc.
9# Copyright (C) 2012 IBM Corp.
10#
11# Authors:
12#  Fam Zheng <famz@redhat.com>
13#
14# This work is licensed under the terms of the GNU GPL, version 2.  See
15# the COPYING file in the top-level directory.
16#
17# Based on qmp.py.
18#
19
20import errno
21from itertools import chain
22import locale
23import logging
24import os
25import shutil
26import signal
27import socket
28import subprocess
29import tempfile
30from types import TracebackType
31from typing import (
32    Any,
33    BinaryIO,
34    Dict,
35    List,
36    Optional,
37    Sequence,
38    Tuple,
39    Type,
40    TypeVar,
41)
42
43from qemu.qmp import SocketAddrT
44from qemu.qmp.legacy import (
45    QEMUMonitorProtocol,
46    QMPMessage,
47    QMPReturnValue,
48)
49
50from . import console_socket
51
52
53LOG = logging.getLogger(__name__)
54
55
56class QEMUMachineError(Exception):
57    """
58    Exception called when an error in QEMUMachine happens.
59    """
60
61
62class QEMUMachineAddDeviceError(QEMUMachineError):
63    """
64    Exception raised when a request to add a device can not be fulfilled
65
66    The failures are caused by limitations, lack of information or conflicting
67    requests on the QEMUMachine methods.  This exception does not represent
68    failures reported by the QEMU binary itself.
69    """
70
71
72class VMLaunchFailure(QEMUMachineError):
73    """
74    Exception raised when a VM launch was attempted, but failed.
75    """
76    def __init__(self, exitcode: Optional[int],
77                 command: str, output: Optional[str]):
78        super().__init__(exitcode, command, output)
79        self.exitcode = exitcode
80        self.command = command
81        self.output = output
82
83    def __str__(self) -> str:
84        ret = ''
85        if self.__cause__ is not None:
86            name = type(self.__cause__).__name__
87            reason = str(self.__cause__)
88            if reason:
89                ret += f"{name}: {reason}"
90            else:
91                ret += f"{name}"
92        ret += '\n'
93
94        if self.exitcode is not None:
95            ret += f"\tExit code: {self.exitcode}\n"
96        ret += f"\tCommand: {self.command}\n"
97        ret += f"\tOutput: {self.output}\n"
98        return ret
99
100
101class AbnormalShutdown(QEMUMachineError):
102    """
103    Exception raised when a graceful shutdown was requested, but not performed.
104    """
105
106
107_T = TypeVar('_T', bound='QEMUMachine')
108
109
110class QEMUMachine:
111    """
112    A QEMU VM.
113
114    Use this object as a context manager to ensure
115    the QEMU process terminates::
116
117        with VM(binary) as vm:
118            ...
119        # vm is guaranteed to be shut down here
120    """
121    # pylint: disable=too-many-instance-attributes, too-many-public-methods
122
123    def __init__(self,
124                 binary: str,
125                 args: Sequence[str] = (),
126                 wrapper: Sequence[str] = (),
127                 name: Optional[str] = None,
128                 base_temp_dir: str = "/var/tmp",
129                 monitor_address: Optional[SocketAddrT] = None,
130                 sock_dir: Optional[str] = None,
131                 drain_console: bool = False,
132                 console_log: Optional[str] = None,
133                 log_dir: Optional[str] = None,
134                 qmp_timer: Optional[float] = None):
135        '''
136        Initialize a QEMUMachine
137
138        @param binary: path to the qemu binary
139        @param args: list of extra arguments
140        @param wrapper: list of arguments used as prefix to qemu binary
141        @param name: prefix for socket and log file names (default: qemu-PID)
142        @param base_temp_dir: default location where temp files are created
143        @param monitor_address: address for QMP monitor
144        @param sock_dir: where to create socket (defaults to base_temp_dir)
145        @param drain_console: (optional) True to drain console socket to buffer
146        @param console_log: (optional) path to console log file
147        @param log_dir: where to create and keep log files
148        @param qmp_timer: (optional) default QMP socket timeout
149        @note: Qemu process is not started until launch() is used.
150        '''
151        # pylint: disable=too-many-arguments
152
153        # Direct user configuration
154
155        self._binary = binary
156        self._args = list(args)
157        self._wrapper = wrapper
158        self._qmp_timer = qmp_timer
159
160        self._name = name or f"qemu-{os.getpid()}-{id(self):02x}"
161        self._temp_dir: Optional[str] = None
162        self._base_temp_dir = base_temp_dir
163        self._sock_dir = sock_dir
164        self._log_dir = log_dir
165
166        if monitor_address is not None:
167            self._monitor_address = monitor_address
168        else:
169            self._monitor_address = os.path.join(
170                self.sock_dir, f"{self._name}-monitor.sock"
171            )
172
173        self._console_log_path = console_log
174        if self._console_log_path:
175            # In order to log the console, buffering needs to be enabled.
176            self._drain_console = True
177        else:
178            self._drain_console = drain_console
179
180        # Runstate
181        self._qemu_log_path: Optional[str] = None
182        self._qemu_log_file: Optional[BinaryIO] = None
183        self._popen: Optional['subprocess.Popen[bytes]'] = None
184        self._events: List[QMPMessage] = []
185        self._iolog: Optional[str] = None
186        self._qmp_set = True   # Enable QMP monitor by default.
187        self._qmp_connection: Optional[QEMUMonitorProtocol] = None
188        self._qemu_full_args: Tuple[str, ...] = ()
189        self._launched = False
190        self._machine: Optional[str] = None
191        self._console_index = 0
192        self._console_set = False
193        self._console_device_type: Optional[str] = None
194        self._console_address = os.path.join(
195            self.sock_dir, f"{self._name}-console.sock"
196        )
197        self._console_socket: Optional[socket.socket] = None
198        self._remove_files: List[str] = []
199        self._user_killed = False
200        self._quit_issued = False
201
202    def __enter__(self: _T) -> _T:
203        return self
204
205    def __exit__(self,
206                 exc_type: Optional[Type[BaseException]],
207                 exc_val: Optional[BaseException],
208                 exc_tb: Optional[TracebackType]) -> None:
209        self.shutdown()
210
211    def add_monitor_null(self) -> None:
212        """
213        This can be used to add an unused monitor instance.
214        """
215        self._args.append('-monitor')
216        self._args.append('null')
217
218    def add_fd(self: _T, fd: int, fdset: int,
219               opaque: str, opts: str = '') -> _T:
220        """
221        Pass a file descriptor to the VM
222        """
223        options = ['fd=%d' % fd,
224                   'set=%d' % fdset,
225                   'opaque=%s' % opaque]
226        if opts:
227            options.append(opts)
228
229        # This did not exist before 3.4, but since then it is
230        # mandatory for our purpose
231        if hasattr(os, 'set_inheritable'):
232            os.set_inheritable(fd, True)
233
234        self._args.append('-add-fd')
235        self._args.append(','.join(options))
236        return self
237
238    def send_fd_scm(self, fd: Optional[int] = None,
239                    file_path: Optional[str] = None) -> int:
240        """
241        Send an fd or file_path to the remote via SCM_RIGHTS.
242
243        Exactly one of fd and file_path must be given.  If it is
244        file_path, the file will be opened read-only and the new file
245        descriptor will be sent to the remote.
246        """
247        if file_path is not None:
248            assert fd is None
249            with open(file_path, "rb") as passfile:
250                fd = passfile.fileno()
251                self._qmp.send_fd_scm(fd)
252        else:
253            assert fd is not None
254            self._qmp.send_fd_scm(fd)
255
256        return 0
257
258    @staticmethod
259    def _remove_if_exists(path: str) -> None:
260        """
261        Remove file object at path if it exists
262        """
263        try:
264            os.remove(path)
265        except OSError as exception:
266            if exception.errno == errno.ENOENT:
267                return
268            raise
269
270    def is_running(self) -> bool:
271        """Returns true if the VM is running."""
272        return self._popen is not None and self._popen.poll() is None
273
274    @property
275    def _subp(self) -> 'subprocess.Popen[bytes]':
276        if self._popen is None:
277            raise QEMUMachineError('Subprocess pipe not present')
278        return self._popen
279
280    def exitcode(self) -> Optional[int]:
281        """Returns the exit code if possible, or None."""
282        if self._popen is None:
283            return None
284        return self._popen.poll()
285
286    def get_pid(self) -> Optional[int]:
287        """Returns the PID of the running process, or None."""
288        if not self.is_running():
289            return None
290        return self._subp.pid
291
292    def _load_io_log(self) -> None:
293        # Assume that the output encoding of QEMU's terminal output is
294        # defined by our locale. If indeterminate, allow open() to fall
295        # back to the platform default.
296        _, encoding = locale.getlocale()
297        if self._qemu_log_path is not None:
298            with open(self._qemu_log_path, "r", encoding=encoding) as iolog:
299                self._iolog = iolog.read()
300
301    @property
302    def _base_args(self) -> List[str]:
303        args = ['-display', 'none', '-vga', 'none']
304
305        if self._qmp_set:
306            if isinstance(self._monitor_address, tuple):
307                moncdev = "socket,id=mon,host={},port={}".format(
308                    *self._monitor_address
309                )
310            else:
311                moncdev = f"socket,id=mon,path={self._monitor_address}"
312            args.extend(['-chardev', moncdev, '-mon',
313                         'chardev=mon,mode=control'])
314
315        if self._machine is not None:
316            args.extend(['-machine', self._machine])
317        for _ in range(self._console_index):
318            args.extend(['-serial', 'null'])
319        if self._console_set:
320            chardev = ('socket,id=console,path=%s,server=on,wait=off' %
321                       self._console_address)
322            args.extend(['-chardev', chardev])
323            if self._console_device_type is None:
324                args.extend(['-serial', 'chardev:console'])
325            else:
326                device = '%s,chardev=console' % self._console_device_type
327                args.extend(['-device', device])
328        return args
329
330    @property
331    def args(self) -> List[str]:
332        """Returns the list of arguments given to the QEMU binary."""
333        return self._args
334
335    def _pre_launch(self) -> None:
336        if self._console_set:
337            self._remove_files.append(self._console_address)
338
339        if self._qmp_set:
340            if isinstance(self._monitor_address, str):
341                self._remove_files.append(self._monitor_address)
342            self._qmp_connection = QEMUMonitorProtocol(
343                self._monitor_address,
344                server=True,
345                nickname=self._name
346            )
347
348        # NOTE: Make sure any opened resources are *definitely* freed in
349        # _post_shutdown()!
350        # pylint: disable=consider-using-with
351        self._qemu_log_path = os.path.join(self.log_dir, self._name + ".log")
352        self._qemu_log_file = open(self._qemu_log_path, 'wb')
353
354        self._iolog = None
355        self._qemu_full_args = tuple(chain(
356            self._wrapper,
357            [self._binary],
358            self._base_args,
359            self._args
360        ))
361
362    def _post_launch(self) -> None:
363        if self._qmp_connection:
364            self._qmp.accept(self._qmp_timer)
365
366    def _close_qemu_log_file(self) -> None:
367        if self._qemu_log_file is not None:
368            self._qemu_log_file.close()
369            self._qemu_log_file = None
370
371    def _post_shutdown(self) -> None:
372        """
373        Called to cleanup the VM instance after the process has exited.
374        May also be called after a failed launch.
375        """
376        try:
377            self._close_qmp_connection()
378        except Exception as err:  # pylint: disable=broad-except
379            LOG.warning(
380                "Exception closing QMP connection: %s",
381                str(err) if str(err) else type(err).__name__
382            )
383        finally:
384            assert self._qmp_connection is None
385
386        self._close_qemu_log_file()
387
388        self._load_io_log()
389
390        self._qemu_log_path = None
391
392        if self._temp_dir is not None:
393            shutil.rmtree(self._temp_dir)
394            self._temp_dir = None
395
396        while len(self._remove_files) > 0:
397            self._remove_if_exists(self._remove_files.pop())
398
399        exitcode = self.exitcode()
400        if (exitcode is not None and exitcode < 0
401                and not (self._user_killed and exitcode == -signal.SIGKILL)):
402            msg = 'qemu received signal %i; command: "%s"'
403            if self._qemu_full_args:
404                command = ' '.join(self._qemu_full_args)
405            else:
406                command = ''
407            LOG.warning(msg, -int(exitcode), command)
408
409        self._quit_issued = False
410        self._user_killed = False
411        self._launched = False
412
413    def launch(self) -> None:
414        """
415        Launch the VM and make sure we cleanup and expose the
416        command line/output in case of exception
417        """
418
419        if self._launched:
420            raise QEMUMachineError('VM already launched')
421
422        try:
423            self._launch()
424        except BaseException as exc:
425            # We may have launched the process but it may
426            # have exited before we could connect via QMP.
427            # Assume the VM didn't launch or is exiting.
428            # If we don't wait for the process, exitcode() may still be
429            # 'None' by the time control is ceded back to the caller.
430            if self._launched:
431                self.wait()
432            else:
433                self._post_shutdown()
434
435            if isinstance(exc, Exception):
436                raise VMLaunchFailure(
437                    exitcode=self.exitcode(),
438                    command=' '.join(self._qemu_full_args),
439                    output=self._iolog
440                ) from exc
441
442            # Don't wrap 'BaseException'; doing so would downgrade
443            # that exception. However, we still want to clean up.
444            raise
445
446    def _launch(self) -> None:
447        """
448        Launch the VM and establish a QMP connection
449        """
450        self._pre_launch()
451        LOG.debug('VM launch command: %r', ' '.join(self._qemu_full_args))
452
453        # Cleaning up of this subprocess is guaranteed by _do_shutdown.
454        # pylint: disable=consider-using-with
455        self._popen = subprocess.Popen(self._qemu_full_args,
456                                       stdin=subprocess.DEVNULL,
457                                       stdout=self._qemu_log_file,
458                                       stderr=subprocess.STDOUT,
459                                       shell=False,
460                                       close_fds=False)
461        self._launched = True
462        self._post_launch()
463
464    def _close_qmp_connection(self) -> None:
465        """
466        Close the underlying QMP connection, if any.
467
468        Dutifully report errors that occurred while closing, but assume
469        that any error encountered indicates an abnormal termination
470        process and not a failure to close.
471        """
472        if self._qmp_connection is None:
473            return
474
475        try:
476            self._qmp.close()
477        except EOFError:
478            # EOF can occur as an Exception here when using the Async
479            # QMP backend. It indicates that the server closed the
480            # stream. If we successfully issued 'quit' at any point,
481            # then this was expected. If the remote went away without
482            # our permission, it's worth reporting that as an abnormal
483            # shutdown case.
484            if not (self._user_killed or self._quit_issued):
485                raise
486        finally:
487            self._qmp_connection = None
488
489    def _early_cleanup(self) -> None:
490        """
491        Perform any cleanup that needs to happen before the VM exits.
492
493        This method may be called twice upon shutdown, once each by soft
494        and hard shutdown in failover scenarios.
495        """
496        # If we keep the console socket open, we may deadlock waiting
497        # for QEMU to exit, while QEMU is waiting for the socket to
498        # become writable.
499        if self._console_socket is not None:
500            self._console_socket.close()
501            self._console_socket = None
502
503    def _hard_shutdown(self) -> None:
504        """
505        Perform early cleanup, kill the VM, and wait for it to terminate.
506
507        :raise subprocess.Timeout: When timeout is exceeds 60 seconds
508            waiting for the QEMU process to terminate.
509        """
510        self._early_cleanup()
511        self._subp.kill()
512        self._subp.wait(timeout=60)
513
514    def _soft_shutdown(self, timeout: Optional[int]) -> None:
515        """
516        Perform early cleanup, attempt to gracefully shut down the VM, and wait
517        for it to terminate.
518
519        :param timeout: Timeout in seconds for graceful shutdown.
520                        A value of None is an infinite wait.
521
522        :raise ConnectionReset: On QMP communication errors
523        :raise subprocess.TimeoutExpired: When timeout is exceeded waiting for
524            the QEMU process to terminate.
525        """
526        self._early_cleanup()
527
528        if self._qmp_connection:
529            try:
530                if not self._quit_issued:
531                    # May raise ExecInterruptedError or StateError if the
532                    # connection dies or has *already* died.
533                    self.qmp('quit')
534            finally:
535                # Regardless, we want to quiesce the connection.
536                self._close_qmp_connection()
537
538        # May raise subprocess.TimeoutExpired
539        self._subp.wait(timeout=timeout)
540
541    def _do_shutdown(self, timeout: Optional[int]) -> None:
542        """
543        Attempt to shutdown the VM gracefully; fallback to a hard shutdown.
544
545        :param timeout: Timeout in seconds for graceful shutdown.
546                        A value of None is an infinite wait.
547
548        :raise AbnormalShutdown: When the VM could not be shut down gracefully.
549            The inner exception will likely be ConnectionReset or
550            subprocess.TimeoutExpired. In rare cases, non-graceful termination
551            may result in its own exceptions, likely subprocess.TimeoutExpired.
552        """
553        try:
554            self._soft_shutdown(timeout)
555        except Exception as exc:
556            self._hard_shutdown()
557            raise AbnormalShutdown("Could not perform graceful shutdown") \
558                from exc
559
560    def shutdown(self,
561                 hard: bool = False,
562                 timeout: Optional[int] = 30) -> None:
563        """
564        Terminate the VM (gracefully if possible) and perform cleanup.
565        Cleanup will always be performed.
566
567        If the VM has not yet been launched, or shutdown(), wait(), or kill()
568        have already been called, this method does nothing.
569
570        :param hard: When true, do not attempt graceful shutdown, and
571                     suppress the SIGKILL warning log message.
572        :param timeout: Optional timeout in seconds for graceful shutdown.
573                        Default 30 seconds, A `None` value is an infinite wait.
574        """
575        if not self._launched:
576            return
577
578        try:
579            if hard:
580                self._user_killed = True
581                self._hard_shutdown()
582            else:
583                self._do_shutdown(timeout)
584        finally:
585            self._post_shutdown()
586
587    def kill(self) -> None:
588        """
589        Terminate the VM forcefully, wait for it to exit, and perform cleanup.
590        """
591        self.shutdown(hard=True)
592
593    def wait(self, timeout: Optional[int] = 30) -> None:
594        """
595        Wait for the VM to power off and perform post-shutdown cleanup.
596
597        :param timeout: Optional timeout in seconds. Default 30 seconds.
598                        A value of `None` is an infinite wait.
599        """
600        self._quit_issued = True
601        self.shutdown(timeout=timeout)
602
603    def set_qmp_monitor(self, enabled: bool = True) -> None:
604        """
605        Set the QMP monitor.
606
607        @param enabled: if False, qmp monitor options will be removed from
608                        the base arguments of the resulting QEMU command
609                        line. Default is True.
610
611        .. note:: Call this function before launch().
612        """
613        self._qmp_set = enabled
614
615    @property
616    def _qmp(self) -> QEMUMonitorProtocol:
617        if self._qmp_connection is None:
618            raise QEMUMachineError("Attempt to access QMP with no connection")
619        return self._qmp_connection
620
621    @classmethod
622    def _qmp_args(cls, conv_keys: bool,
623                  args: Dict[str, Any]) -> Dict[str, object]:
624        if conv_keys:
625            return {k.replace('_', '-'): v for k, v in args.items()}
626
627        return args
628
629    def qmp(self, cmd: str,
630            args_dict: Optional[Dict[str, object]] = None,
631            conv_keys: Optional[bool] = None,
632            **args: Any) -> QMPMessage:
633        """
634        Invoke a QMP command and return the response dict
635        """
636        if args_dict is not None:
637            assert not args
638            assert conv_keys is None
639            args = args_dict
640            conv_keys = False
641
642        if conv_keys is None:
643            conv_keys = True
644
645        qmp_args = self._qmp_args(conv_keys, args)
646        ret = self._qmp.cmd(cmd, args=qmp_args)
647        if cmd == 'quit' and 'error' not in ret and 'return' in ret:
648            self._quit_issued = True
649        return ret
650
651    def command(self, cmd: str,
652                conv_keys: bool = True,
653                **args: Any) -> QMPReturnValue:
654        """
655        Invoke a QMP command.
656        On success return the response dict.
657        On failure raise an exception.
658        """
659        qmp_args = self._qmp_args(conv_keys, args)
660        ret = self._qmp.command(cmd, **qmp_args)
661        if cmd == 'quit':
662            self._quit_issued = True
663        return ret
664
665    def get_qmp_event(self, wait: bool = False) -> Optional[QMPMessage]:
666        """
667        Poll for one queued QMP events and return it
668        """
669        if self._events:
670            return self._events.pop(0)
671        return self._qmp.pull_event(wait=wait)
672
673    def get_qmp_events(self, wait: bool = False) -> List[QMPMessage]:
674        """
675        Poll for queued QMP events and return a list of dicts
676        """
677        events = self._qmp.get_events(wait=wait)
678        events.extend(self._events)
679        del self._events[:]
680        return events
681
682    @staticmethod
683    def event_match(event: Any, match: Optional[Any]) -> bool:
684        """
685        Check if an event matches optional match criteria.
686
687        The match criteria takes the form of a matching subdict. The event is
688        checked to be a superset of the subdict, recursively, with matching
689        values whenever the subdict values are not None.
690
691        This has a limitation that you cannot explicitly check for None values.
692
693        Examples, with the subdict queries on the left:
694         - None matches any object.
695         - {"foo": None} matches {"foo": {"bar": 1}}
696         - {"foo": None} matches {"foo": 5}
697         - {"foo": {"abc": None}} does not match {"foo": {"bar": 1}}
698         - {"foo": {"rab": 2}} matches {"foo": {"bar": 1, "rab": 2}}
699        """
700        if match is None:
701            return True
702
703        try:
704            for key in match:
705                if key in event:
706                    if not QEMUMachine.event_match(event[key], match[key]):
707                        return False
708                else:
709                    return False
710            return True
711        except TypeError:
712            # either match or event wasn't iterable (not a dict)
713            return bool(match == event)
714
715    def event_wait(self, name: str,
716                   timeout: float = 60.0,
717                   match: Optional[QMPMessage] = None) -> Optional[QMPMessage]:
718        """
719        event_wait waits for and returns a named event from QMP with a timeout.
720
721        name: The event to wait for.
722        timeout: QEMUMonitorProtocol.pull_event timeout parameter.
723        match: Optional match criteria. See event_match for details.
724        """
725        return self.events_wait([(name, match)], timeout)
726
727    def events_wait(self,
728                    events: Sequence[Tuple[str, Any]],
729                    timeout: float = 60.0) -> Optional[QMPMessage]:
730        """
731        events_wait waits for and returns a single named event from QMP.
732        In the case of multiple qualifying events, this function returns the
733        first one.
734
735        :param events: A sequence of (name, match_criteria) tuples.
736                       The match criteria are optional and may be None.
737                       See event_match for details.
738        :param timeout: Optional timeout, in seconds.
739                        See QEMUMonitorProtocol.pull_event.
740
741        :raise asyncio.TimeoutError:
742            If timeout was non-zero and no matching events were found.
743
744        :return: A QMP event matching the filter criteria.
745                 If timeout was 0 and no event matched, None.
746        """
747        def _match(event: QMPMessage) -> bool:
748            for name, match in events:
749                if event['event'] == name and self.event_match(event, match):
750                    return True
751            return False
752
753        event: Optional[QMPMessage]
754
755        # Search cached events
756        for event in self._events:
757            if _match(event):
758                self._events.remove(event)
759                return event
760
761        # Poll for new events
762        while True:
763            event = self._qmp.pull_event(wait=timeout)
764            if event is None:
765                # NB: None is only returned when timeout is false-ish.
766                # Timeouts raise asyncio.TimeoutError instead!
767                break
768            if _match(event):
769                return event
770            self._events.append(event)
771
772        return None
773
774    def get_log(self) -> Optional[str]:
775        """
776        After self.shutdown or failed qemu execution, this returns the output
777        of the qemu process.
778        """
779        return self._iolog
780
781    def add_args(self, *args: str) -> None:
782        """
783        Adds to the list of extra arguments to be given to the QEMU binary
784        """
785        self._args.extend(args)
786
787    def set_machine(self, machine_type: str) -> None:
788        """
789        Sets the machine type
790
791        If set, the machine type will be added to the base arguments
792        of the resulting QEMU command line.
793        """
794        self._machine = machine_type
795
796    def set_console(self,
797                    device_type: Optional[str] = None,
798                    console_index: int = 0) -> None:
799        """
800        Sets the device type for a console device
801
802        If set, the console device and a backing character device will
803        be added to the base arguments of the resulting QEMU command
804        line.
805
806        This is a convenience method that will either use the provided
807        device type, or default to a "-serial chardev:console" command
808        line argument.
809
810        The actual setting of command line arguments will be be done at
811        machine launch time, as it depends on the temporary directory
812        to be created.
813
814        @param device_type: the device type, such as "isa-serial".  If
815                            None is given (the default value) a "-serial
816                            chardev:console" command line argument will
817                            be used instead, resorting to the machine's
818                            default device type.
819        @param console_index: the index of the console device to use.
820                              If not zero, the command line will create
821                              'index - 1' consoles and connect them to
822                              the 'null' backing character device.
823        """
824        self._console_set = True
825        self._console_device_type = device_type
826        self._console_index = console_index
827
828    @property
829    def console_socket(self) -> socket.socket:
830        """
831        Returns a socket connected to the console
832        """
833        if self._console_socket is None:
834            self._console_socket = console_socket.ConsoleSocket(
835                self._console_address,
836                file=self._console_log_path,
837                drain=self._drain_console)
838        return self._console_socket
839
840    @property
841    def temp_dir(self) -> str:
842        """
843        Returns a temporary directory to be used for this machine
844        """
845        if self._temp_dir is None:
846            self._temp_dir = tempfile.mkdtemp(prefix="qemu-machine-",
847                                              dir=self._base_temp_dir)
848        return self._temp_dir
849
850    @property
851    def sock_dir(self) -> str:
852        """
853        Returns the directory used for sockfiles by this machine.
854        """
855        if self._sock_dir:
856            return self._sock_dir
857        return self.temp_dir
858
859    @property
860    def log_dir(self) -> str:
861        """
862        Returns a directory to be used for writing logs
863        """
864        if self._log_dir is None:
865            return self.temp_dir
866        return self._log_dir
867