scripts/qemu.py

# QEMU library
#
# 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 qmp.qmp
import shutil
import tempfile


LOG = logging.getLogger(__name__)


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


class MonitorResponseError(qmp.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):
        '''
        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()
        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

        # 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

    # This can be used to add an unused monitor instance.
    def add_monitor_telnet(self, ip, port):
        args = 'tcp:%s:%d,server,nowait,telnet' % (ip, port)
        self._args.append('-monitor')
        self._args.append(args)

    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)

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

    def send_fd_scm(self, fd_file_path):
        # 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)
        fd_param = ["%s" % self._socket_scm_helper,
                    "%d" % self._qmp.get_sock_fd(),
                    "%s" % fd_file_path]
        devnull = open(os.path.devnull, 'rb')
        proc = subprocess.Popen(fd_param, stdin=devnull, stdout=subprocess.PIPE,
                                stderr=subprocess.STDOUT)
        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):
        return self._popen is not None and self._popen.poll() is None

    def exitcode(self):
        if self._popen is None:
            return None
        return self._popen.poll()

    def get_pid(self):
        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
        return ['-chardev', moncdev,
                '-mon', 'chardev=mon,mode=control',
                '-display', 'none', '-vga', 'none']

    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._temp_dir,
                                            self._name + "-monitor.sock")
        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.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

    def launch(self):
        """
        Launch the VM and make sure we cleanup and expose the
        command line/output in case of exception
        """
        self._iolog = None
        self._qemu_full_args = None
        try:
            self._launch()
        except:
            if self.is_running():
                self._popen.kill()
                self._popen.wait()
            self._load_io_log()
            self._post_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)
        self._popen = subprocess.Popen(self._qemu_full_args,
                                       stdin=devnull,
                                       stdout=self._qemu_log_file,
                                       stderr=subprocess.STDOUT,
                                       shell=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):
        '''Terminate the VM and clean up'''
        if self.is_running():
            try:
                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.warn(msg, exitcode, command)

    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.iteritems():
            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.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 len(self._events) > 0:
            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

    def event_wait(self, name, timeout=60.0, match=None):
        '''
        Wait for specified timeout on named event in QMP; optionally filter
        results by match.

        The 'match' is checked to be a recursive subset of the 'event'; skips
        branch processing on match's value None
           {"foo": {"bar": 1}} matches {"foo": None}
           {"foo": {"bar": 1}} does not matches {"foo": {"baz": None}}
        '''
        def event_match(event, match=None):
            if match is None:
                return True

            for key in match:
                if key in event:
                    if isinstance(event[key], dict):
                        if not event_match(event[key], match[key]):
                            return False
                    elif event[key] != match[key]:
                        return False
                else:
                    return False

            return True

        # Search cached events
        for event in self._events:
            if (event['event'] == name) and event_match(event, match):
                self._events.remove(event)
                return event

        # Poll for new events
        while True:
            event = self._qmp.pull_event(wait=timeout)
            if (event['event'] == name) and event_match(event, match):
                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