machine.py

"""
QEMU machine module:

The machine module primarily provides the QEMUMachine class,
which provides facilities for managing the lifetime of a QEMU VM.
"""

# Copyright (C) 2015-2016 Red Hat Inc.
# Copyright (C) 2012 IBM Corp.
#
# Authors:
#  Fam Zheng <famz@redhat.com>
#
# This work is licensed under the terms of the GNU GPL, version 2.  See
# the COPYING file in the top-level directory.
#
# Based on qmp.py.
#

import errno
import logging
import os
import subprocess
import shutil
import socket
import tempfile

from . import qmp

LOG = logging.getLogger(__name__)

class QEMUMachineError(Exception):
    """
    Exception called when an error in QEMUMachine happens.
    """


class QEMUMachineAddDeviceError(QEMUMachineError):
    """
    Exception raised when a request to add a device can not be fulfilled

    The failures are caused by limitations, lack of information or conflicting
    requests on the QEMUMachine methods.  This exception does not represent
    failures reported by the QEMU binary itself.
    """


class MonitorResponseError(qmp.QMPError):
    """
    Represents erroneous QMP monitor reply
    """
    def __init__(self, reply):
        try:
            desc = reply["error"]["desc"]
        except KeyError:
            desc = reply
        super(MonitorResponseError, self).__init__(desc)
        self.reply = reply


class QEMUMachine(object):
    """
    A QEMU VM

    Use this object as a context manager to ensure the QEMU process terminates::

        with VM(binary) as vm:
            ...
        # vm is guaranteed to be shut down here
    """

    def __init__(self, binary, args=None, wrapper=None, name=None,
                 test_dir="/var/tmp", monitor_address=None,
                 socket_scm_helper=None, sock_dir=None):
        '''
        Initialize a QEMUMachine

        @param binary: path to the qemu binary
        @param args: list of extra arguments
        @param wrapper: list of arguments used as prefix to qemu binary
        @param name: prefix for socket and log file names (default: qemu-PID)
        @param test_dir: where to create socket and log file
        @param monitor_address: address for QMP monitor
        @param socket_scm_helper: helper program, required for send_fd_scm()
        @note: Qemu process is not started until launch() is used.
        '''
        if args is None:
            args = []
        if wrapper is None:
            wrapper = []
        if name is None:
            name = "qemu-%d" % os.getpid()
        if sock_dir is None:
            sock_dir = test_dir
        self._name = name
        self._monitor_address = monitor_address
        self._vm_monitor = None
        self._qemu_log_path = None
        self._qemu_log_file = None
        self._popen = None
        self._binary = binary
        self._args = list(args)     # Force copy args in case we modify them
        self._wrapper = wrapper
        self._events = []
        self._iolog = None
        self._socket_scm_helper = socket_scm_helper
        self._qmp = None
        self._qemu_full_args = None
        self._test_dir = test_dir
        self._temp_dir = None
        self._sock_dir = sock_dir
        self._launched = False
        self._machine = None
        self._console_set = False
        self._console_device_type = None
        self._console_address = None
        self._console_socket = None
        self._remove_files = []

        # just in case logging wasn't configured by the main script:
        logging.basicConfig()

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.shutdown()
        return False

    def add_monitor_null(self):
        """
        This can be used to add an unused monitor instance.
        """
        self._args.append('-monitor')
        self._args.append('null')

    def add_fd(self, fd, fdset, opaque, opts=''):
        """
        Pass a file descriptor to the VM
        """
        options = ['fd=%d' % fd,
                   'set=%d' % fdset,
                   'opaque=%s' % opaque]
        if opts:
            options.append(opts)

        # This did not exist before 3.4, but since then it is
        # mandatory for our purpose
        if hasattr(os, 'set_inheritable'):
            os.set_inheritable(fd, True)

        self._args.append('-add-fd')
        self._args.append(','.join(options))
        return self

    def send_fd_scm(self, fd=None, file_path=None):
        """
        Send an fd or file_path to socket_scm_helper.

        Exactly one of fd and file_path must be given.
        If it is file_path, the helper will open that file and pass its own fd.
        """
        # In iotest.py, the qmp should always use unix socket.
        assert self._qmp.is_scm_available()
        if self._socket_scm_helper is None:
            raise QEMUMachineError("No path to socket_scm_helper set")
        if not os.path.exists(self._socket_scm_helper):
            raise QEMUMachineError("%s does not exist" %
                                   self._socket_scm_helper)

        # This did not exist before 3.4, but since then it is
        # mandatory for our purpose
        if hasattr(os, 'set_inheritable'):
            os.set_inheritable(self._qmp.get_sock_fd(), True)
            if fd is not None:
                os.set_inheritable(fd, True)

        fd_param = ["%s" % self._socket_scm_helper,
                    "%d" % self._qmp.get_sock_fd()]

        if file_path is not None:
            assert fd is None
            fd_param.append(file_path)
        else:
            assert fd is not None
            fd_param.append(str(fd))

        devnull = open(os.path.devnull, 'rb')
        proc = subprocess.Popen(fd_param, stdin=devnull, stdout=subprocess.PIPE,
                                stderr=subprocess.STDOUT, close_fds=False)
        output = proc.communicate()[0]
        if output:
            LOG.debug(output)

        return proc.returncode

    @staticmethod
    def _remove_if_exists(path):
        """
        Remove file object at path if it exists
        """
        try:
            os.remove(path)
        except OSError as exception:
            if exception.errno == errno.ENOENT:
                return
            raise

    def is_running(self):
        """Returns true if the VM is running."""
        return self._popen is not None and self._popen.poll() is None

    def exitcode(self):
        """Returns the exit code if possible, or None."""
        if self._popen is None:
            return None
        return self._popen.poll()

    def get_pid(self):
        """Returns the PID of the running process, or None."""
        if not self.is_running():
            return None
        return self._popen.pid

    def _load_io_log(self):
        if self._qemu_log_path is not None:
            with open(self._qemu_log_path, "r") as iolog:
                self._iolog = iolog.read()

    def _base_args(self):
        if isinstance(self._monitor_address, tuple):
            moncdev = "socket,id=mon,host=%s,port=%s" % (
                self._monitor_address[0],
                self._monitor_address[1])
        else:
            moncdev = 'socket,id=mon,path=%s' % self._vm_monitor
        args = ['-chardev', moncdev,
                '-mon', 'chardev=mon,mode=control',
                '-display', 'none', '-vga', 'none']
        if self._machine is not None:
            args.extend(['-machine', self._machine])
        if self._console_set:
            self._console_address = os.path.join(self._sock_dir,
                                                 self._name + "-console.sock")
            self._remove_files.append(self._console_address)
            chardev = ('socket,id=console,path=%s,server,nowait' %
                       self._console_address)
            args.extend(['-chardev', chardev])
            if self._console_device_type is None:
                args.extend(['-serial', 'chardev:console'])
            else:
                device = '%s,chardev=console' % self._console_device_type
                args.extend(['-device', device])
        return args

    def _pre_launch(self):
        self._temp_dir = tempfile.mkdtemp(dir=self._test_dir)
        if self._monitor_address is not None:
            self._vm_monitor = self._monitor_address
        else:
            self._vm_monitor = os.path.join(self._sock_dir,
                                            self._name + "-monitor.sock")
            self._remove_files.append(self._vm_monitor)
        self._qemu_log_path = os.path.join(self._temp_dir, self._name + ".log")
        self._qemu_log_file = open(self._qemu_log_path, 'wb')

        self._qmp = qmp.QEMUMonitorProtocol(self._vm_monitor,
                                            server=True)

    def _post_launch(self):
        self._qmp.accept()

    def _post_shutdown(self):
        if self._qemu_log_file is not None:
            self._qemu_log_file.close()
            self._qemu_log_file = None

        self._qemu_log_path = None

        if self._temp_dir is not None:
            shutil.rmtree(self._temp_dir)
            self._temp_dir = None

        while len(self._remove_files) > 0:
            self._remove_if_exists(self._remove_files.pop())

    def launch(self):
        """
        Launch the VM and make sure we cleanup and expose the
        command line/output in case of exception
        """

        if self._launched:
            raise QEMUMachineError('VM already launched')

        self._iolog = None
        self._qemu_full_args = None
        try:
            self._launch()
            self._launched = True
        except:
            self.shutdown()

            LOG.debug('Error launching VM')
            if self._qemu_full_args:
                LOG.debug('Command: %r', ' '.join(self._qemu_full_args))
            if self._iolog:
                LOG.debug('Output: %r', self._iolog)
            raise

    def _launch(self):
        """
        Launch the VM and establish a QMP connection
        """
        devnull = open(os.path.devnull, 'rb')
        self._pre_launch()
        self._qemu_full_args = (self._wrapper + [self._binary] +
                                self._base_args() + self._args)
        LOG.debug('VM launch command: %r', ' '.join(self._qemu_full_args))
        self._popen = subprocess.Popen(self._qemu_full_args,
                                       stdin=devnull,
                                       stdout=self._qemu_log_file,
                                       stderr=subprocess.STDOUT,
                                       shell=False,
                                       close_fds=False)
        self._post_launch()

    def wait(self):
        """
        Wait for the VM to power off
        """
        self._popen.wait()
        self._qmp.close()
        self._load_io_log()
        self._post_shutdown()

    def shutdown(self, has_quit=False):
        """
        Terminate the VM and clean up
        """
        # If we keep the console socket open, we may deadlock waiting
        # for QEMU to exit, while QEMU is waiting for the socket to
        # become writeable.
        if self._console_socket is not None:
            self._console_socket.close()
            self._console_socket = None

        if self.is_running():
            try:
                if not has_quit:
                    self._qmp.cmd('quit')
                self._qmp.close()
            except:
                self._popen.kill()
            self._popen.wait()

        self._load_io_log()
        self._post_shutdown()

        exitcode = self.exitcode()
        if exitcode is not None and exitcode < 0:
            msg = 'qemu received signal %i: %s'
            if self._qemu_full_args:
                command = ' '.join(self._qemu_full_args)
            else:
                command = ''
            LOG.warning(msg, -exitcode, command)

        self._launched = False

    def qmp(self, cmd, conv_keys=True, **args):
        """
        Invoke a QMP command and return the response dict
        """
        qmp_args = dict()
        for key, value in args.items():
            if conv_keys:
                qmp_args[key.replace('_', '-')] = value
            else:
                qmp_args[key] = value

        return self._qmp.cmd(cmd, args=qmp_args)

    def command(self, cmd, conv_keys=True, **args):
        """
        Invoke a QMP command.
        On success return the response dict.
        On failure raise an exception.
        """
        reply = self.qmp(cmd, conv_keys, **args)
        if reply is None:
            raise qmp.QMPError("Monitor is closed")
        if "error" in reply:
            raise MonitorResponseError(reply)
        return reply["return"]

    def get_qmp_event(self, wait=False):
        """
        Poll for one queued QMP events and return it
        """
        if self._events:
            return self._events.pop(0)
        return self._qmp.pull_event(wait=wait)

    def get_qmp_events(self, wait=False):
        """
        Poll for queued QMP events and return a list of dicts
        """
        events = self._qmp.get_events(wait=wait)
        events.extend(self._events)
        del self._events[:]
        self._qmp.clear_events()
        return events

    @staticmethod
    def event_match(event, match=None):
        """
        Check if an event matches optional match criteria.

        The match criteria takes the form of a matching subdict. The event is
        checked to be a superset of the subdict, recursively, with matching
        values whenever the subdict values are not None.

        This has a limitation that you cannot explicitly check for None values.

        Examples, with the subdict queries on the left:
         - None matches any object.
         - {"foo": None} matches {"foo": {"bar": 1}}
         - {"foo": None} matches {"foo": 5}
         - {"foo": {"abc": None}} does not match {"foo": {"bar": 1}}
         - {"foo": {"rab": 2}} matches {"foo": {"bar": 1, "rab": 2}}
        """
        if match is None:
            return True

        try:
            for key in match:
                if key in event:
                    if not QEMUMachine.event_match(event[key], match[key]):
                        return False
                else:
                    return False
            return True
        except TypeError:
            # either match or event wasn't iterable (not a dict)
            return match == event

    def event_wait(self, name, timeout=60.0, match=None):
        """
        event_wait waits for and returns a named event from QMP with a timeout.

        name: The event to wait for.
        timeout: QEMUMonitorProtocol.pull_event timeout parameter.
        match: Optional match criteria. See event_match for details.
        """
        return self.events_wait([(name, match)], timeout)

    def events_wait(self, events, timeout=60.0):
        """
        events_wait waits for and returns a named event from QMP with a timeout.

        events: a sequence of (name, match_criteria) tuples.
                The match criteria are optional and may be None.
                See event_match for details.
        timeout: QEMUMonitorProtocol.pull_event timeout parameter.
        """
        def _match(event):
            for name, match in events:
                if event['event'] == name and self.event_match(event, match):
                    return True
            return False

        # Search cached events
        for event in self._events:
            if _match(event):
                self._events.remove(event)
                return event

        # Poll for new events
        while True:
            event = self._qmp.pull_event(wait=timeout)
            if _match(event):
                return event
            self._events.append(event)

        return None

    def get_log(self):
        """
        After self.shutdown or failed qemu execution, this returns the output
        of the qemu process.
        """
        return self._iolog

    def add_args(self, *args):
        """
        Adds to the list of extra arguments to be given to the QEMU binary
        """
        self._args.extend(args)

    def set_machine(self, machine_type):
        """
        Sets the machine type

        If set, the machine type will be added to the base arguments
        of the resulting QEMU command line.
        """
        self._machine = machine_type

    def set_console(self, device_type=None):
        """
        Sets the device type for a console device

        If set, the console device and a backing character device will
        be added to the base arguments of the resulting QEMU command
        line.

        This is a convenience method that will either use the provided
        device type, or default to a "-serial chardev:console" command
        line argument.

        The actual setting of command line arguments will be be done at
        machine launch time, as it depends on the temporary directory
        to be created.

        @param device_type: the device type, such as "isa-serial".  If
                            None is given (the default value) a "-serial
                            chardev:console" command line argument will
                            be used instead, resorting to the machine's
                            default device type.
        """
        self._console_set = True
        self._console_device_type = device_type

    @property
    def console_socket(self):
        """
        Returns a socket connected to the console
        """
        if self._console_socket is None:
            self._console_socket = socket.socket(socket.AF_UNIX,
                                                 socket.SOCK_STREAM)
            self._console_socket.connect(self._console_address)
        return self._console_socket