qemu-patch-raspberry4/tests/qemu-iotests/iotests.py

# Common utilities and Python wrappers for qemu-iotests
#
# Copyright (C) 2012 IBM Corp.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#

import os
import re
import subprocess
import unittest
import sys
import struct
import json
import signal
import logging
import atexit
import io
from collections import OrderedDict
import faulthandler

sys.path.append(os.path.join(os.path.dirname(__file__), '..', '..', 'python'))
from qemu import qtest

assert sys.version_info >= (3, 6)

faulthandler.enable()

# This will not work if arguments contain spaces but is necessary if we
# want to support the override options that ./check supports.
qemu_img_args = [os.environ.get('QEMU_IMG_PROG', 'qemu-img')]
if os.environ.get('QEMU_IMG_OPTIONS'):
    qemu_img_args += os.environ['QEMU_IMG_OPTIONS'].strip().split(' ')

qemu_io_args = [os.environ.get('QEMU_IO_PROG', 'qemu-io')]
if os.environ.get('QEMU_IO_OPTIONS'):
    qemu_io_args += os.environ['QEMU_IO_OPTIONS'].strip().split(' ')

qemu_io_args_no_fmt = [os.environ.get('QEMU_IO_PROG', 'qemu-io')]
if os.environ.get('QEMU_IO_OPTIONS_NO_FMT'):
    qemu_io_args_no_fmt += \
        os.environ['QEMU_IO_OPTIONS_NO_FMT'].strip().split(' ')

qemu_nbd_args = [os.environ.get('QEMU_NBD_PROG', 'qemu-nbd')]
if os.environ.get('QEMU_NBD_OPTIONS'):
    qemu_nbd_args += os.environ['QEMU_NBD_OPTIONS'].strip().split(' ')

qemu_prog = os.environ.get('QEMU_PROG', 'qemu')
qemu_opts = os.environ.get('QEMU_OPTIONS', '').strip().split(' ')

imgfmt = os.environ.get('IMGFMT', 'raw')
imgproto = os.environ.get('IMGPROTO', 'file')
test_dir = os.environ.get('TEST_DIR')
sock_dir = os.environ.get('SOCK_DIR')
output_dir = os.environ.get('OUTPUT_DIR', '.')
cachemode = os.environ.get('CACHEMODE')
aiomode = os.environ.get('AIOMODE')
qemu_default_machine = os.environ.get('QEMU_DEFAULT_MACHINE')

socket_scm_helper = os.environ.get('SOCKET_SCM_HELPER', 'socket_scm_helper')

luks_default_secret_object = 'secret,id=keysec0,data=' + \
                             os.environ.get('IMGKEYSECRET', '')
luks_default_key_secret_opt = 'key-secret=keysec0'


def qemu_img(*args):
    '''Run qemu-img and return the exit code'''
    devnull = open('/dev/null', 'r+')
    exitcode = subprocess.call(qemu_img_args + list(args), stdin=devnull, stdout=devnull)
    if exitcode < 0:
        sys.stderr.write('qemu-img received signal %i: %s\n' % (-exitcode, ' '.join(qemu_img_args + list(args))))
    return exitcode

def ordered_qmp(qmsg, conv_keys=True):
    # Dictionaries are not ordered prior to 3.6, therefore:
    if isinstance(qmsg, list):
        return [ordered_qmp(atom) for atom in qmsg]
    if isinstance(qmsg, dict):
        od = OrderedDict()
        for k, v in sorted(qmsg.items()):
            if conv_keys:
                k = k.replace('_', '-')
            od[k] = ordered_qmp(v, conv_keys=False)
        return od
    return qmsg

def qemu_img_create(*args):
    args = list(args)

    # default luks support
    if '-f' in args and args[args.index('-f') + 1] == 'luks':
        if '-o' in args:
            i = args.index('-o')
            if 'key-secret' not in args[i + 1]:
                args[i + 1].append(luks_default_key_secret_opt)
                args.insert(i + 2, '--object')
                args.insert(i + 3, luks_default_secret_object)
        else:
            args = ['-o', luks_default_key_secret_opt,
                    '--object', luks_default_secret_object] + args

    args.insert(0, 'create')

    return qemu_img(*args)

def qemu_img_verbose(*args):
    '''Run qemu-img without suppressing its output and return the exit code'''
    exitcode = subprocess.call(qemu_img_args + list(args))
    if exitcode < 0:
        sys.stderr.write('qemu-img received signal %i: %s\n' % (-exitcode, ' '.join(qemu_img_args + list(args))))
    return exitcode

def qemu_img_pipe(*args):
    '''Run qemu-img and return its output'''
    subp = subprocess.Popen(qemu_img_args + list(args),
                            stdout=subprocess.PIPE,
                            stderr=subprocess.STDOUT,
                            universal_newlines=True)
    exitcode = subp.wait()
    if exitcode < 0:
        sys.stderr.write('qemu-img received signal %i: %s\n' % (-exitcode, ' '.join(qemu_img_args + list(args))))
    return subp.communicate()[0]

def qemu_img_log(*args):
    result = qemu_img_pipe(*args)
    log(result, filters=[filter_testfiles])
    return result

def img_info_log(filename, filter_path=None, imgopts=False, extra_args=[]):
    args = ['info']
    if imgopts:
        args.append('--image-opts')
    else:
        args += ['-f', imgfmt]
    args += extra_args
    args.append(filename)

    output = qemu_img_pipe(*args)
    if not filter_path:
        filter_path = filename
    log(filter_img_info(output, filter_path))

def qemu_io(*args):
    '''Run qemu-io and return the stdout data'''
    args = qemu_io_args + list(args)
    subp = subprocess.Popen(args, stdout=subprocess.PIPE,
                            stderr=subprocess.STDOUT,
                            universal_newlines=True)
    exitcode = subp.wait()
    if exitcode < 0:
        sys.stderr.write('qemu-io received signal %i: %s\n' % (-exitcode, ' '.join(args)))
    return subp.communicate()[0]

def qemu_io_log(*args):
    result = qemu_io(*args)
    log(result, filters=[filter_testfiles, filter_qemu_io])
    return result

def qemu_io_silent(*args):
    '''Run qemu-io and return the exit code, suppressing stdout'''
    args = qemu_io_args + list(args)
    exitcode = subprocess.call(args, stdout=open('/dev/null', 'w'))
    if exitcode < 0:
        sys.stderr.write('qemu-io received signal %i: %s\n' %
                         (-exitcode, ' '.join(args)))
    return exitcode

def qemu_io_silent_check(*args):
    '''Run qemu-io and return the true if subprocess returned 0'''
    args = qemu_io_args + list(args)
    exitcode = subprocess.call(args, stdout=open('/dev/null', 'w'),
                               stderr=subprocess.STDOUT)
    return exitcode == 0

def get_virtio_scsi_device():
    if qemu_default_machine == 's390-ccw-virtio':
        return 'virtio-scsi-ccw'
    return 'virtio-scsi-pci'

class QemuIoInteractive:
    def __init__(self, *args):
        self.args = qemu_io_args + list(args)
        self._p = subprocess.Popen(self.args, stdin=subprocess.PIPE,
                                   stdout=subprocess.PIPE,
                                   stderr=subprocess.STDOUT,
                                   universal_newlines=True)
        assert self._p.stdout.read(9) == 'qemu-io> '

    def close(self):
        self._p.communicate('q\n')

    def _read_output(self):
        pattern = 'qemu-io> '
        n = len(pattern)
        pos = 0
        s = []
        while pos != n:
            c = self._p.stdout.read(1)
            # check unexpected EOF
            assert c != ''
            s.append(c)
            if c == pattern[pos]:
                pos += 1
            else:
                pos = 0

        return ''.join(s[:-n])

    def cmd(self, cmd):
        # quit command is in close(), '\n' is added automatically
        assert '\n' not in cmd
        cmd = cmd.strip()
        assert cmd not in ('q', 'quit')
        self._p.stdin.write(cmd + '\n')
        self._p.stdin.flush()
        return self._read_output()


def qemu_nbd(*args):
    '''Run qemu-nbd in daemon mode and return the parent's exit code'''
    return subprocess.call(qemu_nbd_args + ['--fork'] + list(args))

def qemu_nbd_early_pipe(*args):
    '''Run qemu-nbd in daemon mode and return both the parent's exit code
       and its output in case of an error'''
    subp = subprocess.Popen(qemu_nbd_args + ['--fork'] + list(args),
                            stdout=subprocess.PIPE,
                            stderr=subprocess.STDOUT,
                            universal_newlines=True)
    exitcode = subp.wait()
    if exitcode < 0:
        sys.stderr.write('qemu-nbd received signal %i: %s\n' %
                         (-exitcode,
                          ' '.join(qemu_nbd_args + ['--fork'] + list(args))))

    return exitcode, subp.communicate()[0] if exitcode else ''

def qemu_nbd_popen(*args):
    '''Run qemu-nbd in daemon mode and return the parent's exit code'''
    return subprocess.Popen(qemu_nbd_args + ['--persistent'] + list(args))

def compare_images(img1, img2, fmt1=imgfmt, fmt2=imgfmt):
    '''Return True if two image files are identical'''
    return qemu_img('compare', '-f', fmt1,
                    '-F', fmt2, img1, img2) == 0

def create_image(name, size):
    '''Create a fully-allocated raw image with sector markers'''
    file = open(name, 'wb')
    i = 0
    while i < size:
        sector = struct.pack('>l504xl', i // 512, i // 512)
        file.write(sector)
        i = i + 512
    file.close()

def image_size(img):
    '''Return image's virtual size'''
    r = qemu_img_pipe('info', '--output=json', '-f', imgfmt, img)
    return json.loads(r)['virtual-size']

def is_str(val):
    return isinstance(val, str)

test_dir_re = re.compile(r"%s" % test_dir)
def filter_test_dir(msg):
    return test_dir_re.sub("TEST_DIR", msg)

win32_re = re.compile(r"\r")
def filter_win32(msg):
    return win32_re.sub("", msg)

qemu_io_re = re.compile(r"[0-9]* ops; [0-9\/:. sec]* \([0-9\/.inf]* [EPTGMKiBbytes]*\/sec and [0-9\/.inf]* ops\/sec\)")
def filter_qemu_io(msg):
    msg = filter_win32(msg)
    return qemu_io_re.sub("X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)", msg)

chown_re = re.compile(r"chown [0-9]+:[0-9]+")
def filter_chown(msg):
    return chown_re.sub("chown UID:GID", msg)

def filter_qmp_event(event):
    '''Filter a QMP event dict'''
    event = dict(event)
    if 'timestamp' in event:
        event['timestamp']['seconds'] = 'SECS'
        event['timestamp']['microseconds'] = 'USECS'
    return event

def filter_qmp(qmsg, filter_fn):
    '''Given a string filter, filter a QMP object's values.
    filter_fn takes a (key, value) pair.'''
    # Iterate through either lists or dicts;
    if isinstance(qmsg, list):
        items = enumerate(qmsg)
    else:
        items = qmsg.items()

    for k, v in items:
        if isinstance(v, (dict, list)):
            qmsg[k] = filter_qmp(v, filter_fn)
        else:
            qmsg[k] = filter_fn(k, v)
    return qmsg

def filter_testfiles(msg):
    prefix = os.path.join(test_dir, "%s-" % (os.getpid()))
    return msg.replace(prefix, 'TEST_DIR/PID-')

def filter_qmp_testfiles(qmsg):
    def _filter(_key, value):
        if is_str(value):
            return filter_testfiles(value)
        return value
    return filter_qmp(qmsg, _filter)

def filter_generated_node_ids(msg):
    return re.sub("#block[0-9]+", "NODE_NAME", msg)

def filter_img_info(output, filename):
    lines = []
    for line in output.split('\n'):
        if 'disk size' in line or 'actual-size' in line:
            continue
        line = line.replace(filename, 'TEST_IMG')
        line = filter_testfiles(line)
        line = line.replace(imgfmt, 'IMGFMT')
        line = re.sub('iters: [0-9]+', 'iters: XXX', line)
        line = re.sub('uuid: [-a-f0-9]+', 'uuid: XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX', line)
        line = re.sub('cid: [0-9]+', 'cid: XXXXXXXXXX', line)
        lines.append(line)
    return '\n'.join(lines)

def filter_imgfmt(msg):
    return msg.replace(imgfmt, 'IMGFMT')

def filter_qmp_imgfmt(qmsg):
    def _filter(_key, value):
        if is_str(value):
            return filter_imgfmt(value)
        return value
    return filter_qmp(qmsg, _filter)

def log(msg, filters=[], indent=None):
    '''Logs either a string message or a JSON serializable message (like QMP).
    If indent is provided, JSON serializable messages are pretty-printed.'''
    for flt in filters:
        msg = flt(msg)
    if isinstance(msg, (dict, list)):
        # Python < 3.4 needs to know not to add whitespace when pretty-printing:
        separators = (', ', ': ') if indent is None else (',', ': ')
        # Don't sort if it's already sorted
        do_sort = not isinstance(msg, OrderedDict)
        print(json.dumps(msg, sort_keys=do_sort,
                         indent=indent, separators=separators))
    else:
        print(msg)

class Timeout:
    def __init__(self, seconds, errmsg="Timeout"):
        self.seconds = seconds
        self.errmsg = errmsg
    def __enter__(self):
        signal.signal(signal.SIGALRM, self.timeout)
        signal.setitimer(signal.ITIMER_REAL, self.seconds)
        return self
    def __exit__(self, exc_type, value, traceback):
        signal.setitimer(signal.ITIMER_REAL, 0)
        return False
    def timeout(self, signum, frame):
        raise Exception(self.errmsg)

def file_pattern(name):
    return "{0}-{1}".format(os.getpid(), name)

class FilePaths:
    """
    FilePaths is an auto-generated filename that cleans itself up.

    Use this context manager to generate filenames and ensure that the file
    gets deleted::

        with FilePaths(['test.img']) as img_path:
            qemu_img('create', img_path, '1G')
        # migration_sock_path is automatically deleted
    """
    def __init__(self, names, base_dir=test_dir):
        self.paths = []
        for name in names:
            self.paths.append(os.path.join(base_dir, file_pattern(name)))

    def __enter__(self):
        return self.paths

    def __exit__(self, exc_type, exc_val, exc_tb):
        try:
            for path in self.paths:
                os.remove(path)
        except OSError:
            pass
        return False

class FilePath(FilePaths):
    """
    FilePath is a specialization of FilePaths that takes a single filename.
    """
    def __init__(self, name, base_dir=test_dir):
        super(FilePath, self).__init__([name], base_dir)

    def __enter__(self):
        return self.paths[0]

def file_path_remover():
    for path in reversed(file_path_remover.paths):
        try:
            os.remove(path)
        except OSError:
            pass


def file_path(*names, base_dir=test_dir):
    ''' Another way to get auto-generated filename that cleans itself up.

    Use is as simple as:

    img_a, img_b = file_path('a.img', 'b.img')
    sock = file_path('socket')
    '''

    if not hasattr(file_path_remover, 'paths'):
        file_path_remover.paths = []
        atexit.register(file_path_remover)

    paths = []
    for name in names:
        filename = file_pattern(name)
        path = os.path.join(base_dir, filename)
        file_path_remover.paths.append(path)
        paths.append(path)

    return paths[0] if len(paths) == 1 else paths

def remote_filename(path):
    if imgproto == 'file':
        return path
    elif imgproto == 'ssh':
        return "ssh://%s@127.0.0.1:22%s" % (os.environ.get('USER'), path)
    else:
        raise Exception("Protocol %s not supported" % (imgproto))

class VM(qtest.QEMUQtestMachine):
    '''A QEMU VM'''

    def __init__(self, path_suffix=''):
        name = "qemu%s-%d" % (path_suffix, os.getpid())
        super(VM, self).__init__(qemu_prog, qemu_opts, name=name,
                                 test_dir=test_dir,
                                 socket_scm_helper=socket_scm_helper,
                                 sock_dir=sock_dir)
        self._num_drives = 0

    def add_object(self, opts):
        self._args.append('-object')
        self._args.append(opts)
        return self

    def add_device(self, opts):
        self._args.append('-device')
        self._args.append(opts)
        return self

    def add_drive_raw(self, opts):
        self._args.append('-drive')
        self._args.append(opts)
        return self

    def add_drive(self, path, opts='', interface='virtio', format=imgfmt):
        '''Add a virtio-blk drive to the VM'''
        options = ['if=%s' % interface,
                   'id=drive%d' % self._num_drives]

        if path is not None:
            options.append('file=%s' % path)
            options.append('format=%s' % format)
            options.append('cache=%s' % cachemode)
            options.append('aio=%s' % aiomode)

        if opts:
            options.append(opts)

        if format == 'luks' and 'key-secret' not in opts:
            # default luks support
            if luks_default_secret_object not in self._args:
                self.add_object(luks_default_secret_object)

            options.append(luks_default_key_secret_opt)

        self._args.append('-drive')
        self._args.append(','.join(options))
        self._num_drives += 1
        return self

    def add_blockdev(self, opts):
        self._args.append('-blockdev')
        if isinstance(opts, str):
            self._args.append(opts)
        else:
            self._args.append(','.join(opts))
        return self

    def add_incoming(self, addr):
        self._args.append('-incoming')
        self._args.append(addr)
        return self

    def pause_drive(self, drive, event=None):
        '''Pause drive r/w operations'''
        if not event:
            self.pause_drive(drive, "read_aio")
            self.pause_drive(drive, "write_aio")
            return
        self.qmp('human-monitor-command',
                 command_line='qemu-io %s "break %s bp_%s"' % (drive, event, drive))

    def resume_drive(self, drive):
        self.qmp('human-monitor-command',
                 command_line='qemu-io %s "remove_break bp_%s"' % (drive, drive))

    def hmp_qemu_io(self, drive, cmd):
        '''Write to a given drive using an HMP command'''
        return self.qmp('human-monitor-command',
                        command_line='qemu-io %s "%s"' % (drive, cmd))

    def flatten_qmp_object(self, obj, output=None, basestr=''):
        if output is None:
            output = dict()
        if isinstance(obj, list):
            for i, item in enumerate(obj):
                self.flatten_qmp_object(item, output, basestr + str(i) + '.')
        elif isinstance(obj, dict):
            for key in obj:
                self.flatten_qmp_object(obj[key], output, basestr + key + '.')
        else:
            output[basestr[:-1]] = obj # Strip trailing '.'
        return output

    def qmp_to_opts(self, obj):
        obj = self.flatten_qmp_object(obj)
        output_list = list()
        for key in obj:
            output_list += [key + '=' + obj[key]]
        return ','.join(output_list)

    def get_qmp_events_filtered(self, wait=60.0):
        result = []
        for ev in self.get_qmp_events(wait=wait):
            result.append(filter_qmp_event(ev))
        return result

    def qmp_log(self, cmd, filters=[], indent=None, **kwargs):
        full_cmd = OrderedDict((
            ("execute", cmd),
            ("arguments", ordered_qmp(kwargs))
        ))
        log(full_cmd, filters, indent=indent)
        result = self.qmp(cmd, **kwargs)
        log(result, filters, indent=indent)
        return result

    # Returns None on success, and an error string on failure
    def run_job(self, job, auto_finalize=True, auto_dismiss=False,
                pre_finalize=None, cancel=False, use_log=True, wait=60.0):
        """
        run_job moves a job from creation through to dismissal.

        :param job: String. ID of recently-launched job
        :param auto_finalize: Bool. True if the job was launched with
                              auto_finalize. Defaults to True.
        :param auto_dismiss: Bool. True if the job was launched with
                             auto_dismiss=True. Defaults to False.
        :param pre_finalize: Callback. A callable that takes no arguments to be
                             invoked prior to issuing job-finalize, if any.
        :param cancel: Bool. When true, cancels the job after the pre_finalize
                       callback.
        :param use_log: Bool. When false, does not log QMP messages.
        :param wait: Float. Timeout value specifying how long to wait for any
                     event, in seconds. Defaults to 60.0.
        """
        match_device = {'data': {'device': job}}
        match_id = {'data': {'id': job}}
        events = [
            ('BLOCK_JOB_COMPLETED', match_device),
            ('BLOCK_JOB_CANCELLED', match_device),
            ('BLOCK_JOB_ERROR', match_device),
            ('BLOCK_JOB_READY', match_device),
            ('BLOCK_JOB_PENDING', match_id),
            ('JOB_STATUS_CHANGE', match_id)
        ]
        error = None
        while True:
            ev = filter_qmp_event(self.events_wait(events, timeout=wait))
            if ev['event'] != 'JOB_STATUS_CHANGE':
                if use_log:
                    log(ev)
                continue
            status = ev['data']['status']
            if status == 'aborting':
                result = self.qmp('query-jobs')
                for j in result['return']:
                    if j['id'] == job:
                        error = j['error']
                        if use_log:
                            log('Job failed: %s' % (j['error']))
            elif status == 'ready':
                if use_log:
                    self.qmp_log('job-complete', id=job)
                else:
                    self.qmp('job-complete', id=job)
            elif status == 'pending' and not auto_finalize:
                if pre_finalize:
                    pre_finalize()
                if cancel and use_log:
                    self.qmp_log('job-cancel', id=job)
                elif cancel:
                    self.qmp('job-cancel', id=job)
                elif use_log:
                    self.qmp_log('job-finalize', id=job)
                else:
                    self.qmp('job-finalize', id=job)
            elif status == 'concluded' and not auto_dismiss:
                if use_log:
                    self.qmp_log('job-dismiss', id=job)
                else:
                    self.qmp('job-dismiss', id=job)
            elif status == 'null':
                return error

    # Returns None on success, and an error string on failure
    def blockdev_create(self, options, job_id='job0', filters=None):
        if filters is None:
            filters = [filter_qmp_testfiles]
        result = self.qmp_log('blockdev-create', filters=filters,
                              job_id=job_id, options=options)

        if 'return' in result:
            assert result['return'] == {}
            job_result = self.run_job(job_id)
        else:
            job_result = result['error']

        log("")
        return job_result

    def enable_migration_events(self, name):
        log('Enabling migration QMP events on %s...' % name)
        log(self.qmp('migrate-set-capabilities', capabilities=[
            {
                'capability': 'events',
                'state': True
            }
        ]))

    def wait_migration(self, expect_runstate):
        while True:
            event = self.event_wait('MIGRATION')
            log(event, filters=[filter_qmp_event])
            if event['data']['status'] == 'completed':
                break
        # The event may occur in finish-migrate, so wait for the expected
        # post-migration runstate
        while self.qmp('query-status')['return']['status'] != expect_runstate:
            pass

    def node_info(self, node_name):
        nodes = self.qmp('query-named-block-nodes')
        for x in nodes['return']:
            if x['node-name'] == node_name:
                return x
        return None

    def query_bitmaps(self):
        res = self.qmp("query-named-block-nodes")
        return {device['node-name']: device['dirty-bitmaps']
                for device in res['return'] if 'dirty-bitmaps' in device}

    def get_bitmap(self, node_name, bitmap_name, recording=None, bitmaps=None):
        """
        get a specific bitmap from the object returned by query_bitmaps.
        :param recording: If specified, filter results by the specified value.
        :param bitmaps: If specified, use it instead of call query_bitmaps()
        """
        if bitmaps is None:
            bitmaps = self.query_bitmaps()

        for bitmap in bitmaps[node_name]:
            if bitmap.get('name', '') == bitmap_name:
                if recording is None or bitmap.get('recording') == recording:
                    return bitmap
        return None

    def check_bitmap_status(self, node_name, bitmap_name, fields):
        ret = self.get_bitmap(node_name, bitmap_name)

        return fields.items() <= ret.items()

    def assert_block_path(self, root, path, expected_node, graph=None):
        """
        Check whether the node under the given path in the block graph
        is @expected_node.

        @root is the node name of the node where the @path is rooted.

        @path is a string that consists of child names separated by
        slashes.  It must begin with a slash.

        Examples for @root + @path:
          - root="qcow2-node", path="/backing/file"
          - root="quorum-node", path="/children.2/file"

        Hypothetically, @path could be empty, in which case it would
        point to @root.  However, in practice this case is not useful
        and hence not allowed.

        @expected_node may be None.  (All elements of the path but the
        leaf must still exist.)

        @graph may be None or the result of an x-debug-query-block-graph
        call that has already been performed.
        """
        if graph is None:
            graph = self.qmp('x-debug-query-block-graph')['return']

        iter_path = iter(path.split('/'))

        # Must start with a /
        assert next(iter_path) == ''

        node = next((node for node in graph['nodes'] if node['name'] == root),
                    None)

        # An empty @path is not allowed, so the root node must be present
        assert node is not None, 'Root node %s not found' % root

        for child_name in iter_path:
            assert node is not None, 'Cannot follow path %s%s' % (root, path)

            try:
                node_id = next(edge['child'] for edge in graph['edges']
                               if (edge['parent'] == node['id'] and
                                   edge['name'] == child_name))

                node = next(node for node in graph['nodes']
                            if node['id'] == node_id)

            except StopIteration:
                node = None

        if node is None:
            assert expected_node is None, \
                   'No node found under %s (but expected %s)' % \
                   (path, expected_node)
        else:
            assert node['name'] == expected_node, \
                   'Found node %s under %s (but expected %s)' % \
                   (node['name'], path, expected_node)

index_re = re.compile(r'([^\[]+)\[([^\]]+)\]')

class QMPTestCase(unittest.TestCase):
    '''Abstract base class for QMP test cases'''

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        # Many users of this class set a VM property we rely on heavily
        # in the methods below.
        self.vm = None

    def dictpath(self, d, path):
        '''Traverse a path in a nested dict'''
        for component in path.split('/'):
            m = index_re.match(component)
            if m:
                component, idx = m.groups()
                idx = int(idx)

            if not isinstance(d, dict) or component not in d:
                self.fail('failed path traversal for "%s" in "%s"' % (path, str(d)))
            d = d[component]

            if m:
                if not isinstance(d, list):
                    self.fail('path component "%s" in "%s" is not a list in "%s"' % (component, path, str(d)))
                try:
                    d = d[idx]
                except IndexError:
                    self.fail('invalid index "%s" in path "%s" in "%s"' % (idx, path, str(d)))
        return d

    def assert_qmp_absent(self, d, path):
        try:
            result = self.dictpath(d, path)
        except AssertionError:
            return
        self.fail('path "%s" has value "%s"' % (path, str(result)))

    def assert_qmp(self, d, path, value):
        '''Assert that the value for a specific path in a QMP dict
           matches.  When given a list of values, assert that any of
           them matches.'''

        result = self.dictpath(d, path)

        # [] makes no sense as a list of valid values, so treat it as
        # an actual single value.
        if isinstance(value, list) and value != []:
            for v in value:
                if result == v:
                    return
            self.fail('no match for "%s" in %s' % (str(result), str(value)))
        else:
            self.assertEqual(result, value,
                             '"%s" is "%s", expected "%s"'
                             % (path, str(result), str(value)))

    def assert_no_active_block_jobs(self):
        result = self.vm.qmp('query-block-jobs')
        self.assert_qmp(result, 'return', [])

    def assert_has_block_node(self, node_name=None, file_name=None):
        """Issue a query-named-block-nodes and assert node_name and/or
        file_name is present in the result"""
        def check_equal_or_none(a, b):
            return a is None or b is None or a == b
        assert node_name or file_name
        result = self.vm.qmp('query-named-block-nodes')
        for x in result["return"]:
            if check_equal_or_none(x.get("node-name"), node_name) and \
                    check_equal_or_none(x.get("file"), file_name):
                return
        self.fail("Cannot find %s %s in result:\n%s" %
                  (node_name, file_name, result))

    def assert_json_filename_equal(self, json_filename, reference):
        '''Asserts that the given filename is a json: filename and that its
           content is equal to the given reference object'''
        self.assertEqual(json_filename[:5], 'json:')
        self.assertEqual(self.vm.flatten_qmp_object(json.loads(json_filename[5:])),
                         self.vm.flatten_qmp_object(reference))

    def cancel_and_wait(self, drive='drive0', force=False, resume=False, wait=60.0):
        '''Cancel a block job and wait for it to finish, returning the event'''
        result = self.vm.qmp('block-job-cancel', device=drive, force=force)
        self.assert_qmp(result, 'return', {})

        if resume:
            self.vm.resume_drive(drive)

        cancelled = False
        result = None
        while not cancelled:
            for event in self.vm.get_qmp_events(wait=wait):
                if event['event'] == 'BLOCK_JOB_COMPLETED' or \
                   event['event'] == 'BLOCK_JOB_CANCELLED':
                    self.assert_qmp(event, 'data/device', drive)
                    result = event
                    cancelled = True
                elif event['event'] == 'JOB_STATUS_CHANGE':
                    self.assert_qmp(event, 'data/id', drive)


        self.assert_no_active_block_jobs()
        return result

    def wait_until_completed(self, drive='drive0', check_offset=True, wait=60.0,
                             error=None):
        '''Wait for a block job to finish, returning the event'''
        while True:
            for event in self.vm.get_qmp_events(wait=wait):
                if event['event'] == 'BLOCK_JOB_COMPLETED':
                    self.assert_qmp(event, 'data/device', drive)
                    if error is None:
                        self.assert_qmp_absent(event, 'data/error')
                        if check_offset:
                            self.assert_qmp(event, 'data/offset',
                                            event['data']['len'])
                    else:
                        self.assert_qmp(event, 'data/error', error)
                    self.assert_no_active_block_jobs()
                    return event
                if event['event'] == 'JOB_STATUS_CHANGE':
                    self.assert_qmp(event, 'data/id', drive)

    def wait_ready(self, drive='drive0'):
        """Wait until a BLOCK_JOB_READY event, and return the event."""
        f = {'data': {'type': 'mirror', 'device': drive}}
        return self.vm.event_wait(name='BLOCK_JOB_READY', match=f)

    def wait_ready_and_cancel(self, drive='drive0'):
        self.wait_ready(drive=drive)
        event = self.cancel_and_wait(drive=drive)
        self.assertEqual(event['event'], 'BLOCK_JOB_COMPLETED')
        self.assert_qmp(event, 'data/type', 'mirror')
        self.assert_qmp(event, 'data/offset', event['data']['len'])

    def complete_and_wait(self, drive='drive0', wait_ready=True,
                          completion_error=None):
        '''Complete a block job and wait for it to finish'''
        if wait_ready:
            self.wait_ready(drive=drive)

        result = self.vm.qmp('block-job-complete', device=drive)
        self.assert_qmp(result, 'return', {})

        event = self.wait_until_completed(drive=drive, error=completion_error)
        self.assert_qmp(event, 'data/type', 'mirror')

    def pause_wait(self, job_id='job0'):
        with Timeout(3, "Timeout waiting for job to pause"):
            while True:
                result = self.vm.qmp('query-block-jobs')
                found = False
                for job in result['return']:
                    if job['device'] == job_id:
                        found = True
                        if job['paused'] and not job['busy']:
                            return job
                        break
                assert found

    def pause_job(self, job_id='job0', wait=True):
        result = self.vm.qmp('block-job-pause', device=job_id)
        self.assert_qmp(result, 'return', {})
        if wait:
            return self.pause_wait(job_id)
        return result

    def case_skip(self, reason):
        '''Skip this test case'''
        case_notrun(reason)
        self.skipTest(reason)


def notrun(reason):
    '''Skip this test suite'''
    # Each test in qemu-iotests has a number ("seq")
    seq = os.path.basename(sys.argv[0])

    open('%s/%s.notrun' % (output_dir, seq), 'w').write(reason + '\n')
    print('%s not run: %s' % (seq, reason))
    sys.exit(0)

def case_notrun(reason):
    '''Mark this test case as not having been run (without actually
    skipping it, that is left to the caller).  See
    QMPTestCase.case_skip() for a variant that actually skips the
    current test case.'''

    # Each test in qemu-iotests has a number ("seq")
    seq = os.path.basename(sys.argv[0])

    open('%s/%s.casenotrun' % (output_dir, seq), 'a').write(
        '    [case not run] ' + reason + '\n')

def verify_image_format(supported_fmts=[], unsupported_fmts=[]):
    assert not (supported_fmts and unsupported_fmts)

    if 'generic' in supported_fmts and \
            os.environ.get('IMGFMT_GENERIC', 'true') == 'true':
        # similar to
        #   _supported_fmt generic
        # for bash tests
        return

    not_sup = supported_fmts and (imgfmt not in supported_fmts)
    if not_sup or (imgfmt in unsupported_fmts):
        notrun('not suitable for this image format: %s' % imgfmt)

def verify_protocol(supported=[], unsupported=[]):
    assert not (supported and unsupported)

    if 'generic' in supported:
        return

    not_sup = supported and (imgproto not in supported)
    if not_sup or (imgproto in unsupported):
        notrun('not suitable for this protocol: %s' % imgproto)

def verify_platform(supported=None, unsupported=None):
    if unsupported is not None:
        if any((sys.platform.startswith(x) for x in unsupported)):
            notrun('not suitable for this OS: %s' % sys.platform)

    if supported is not None:
        if not any((sys.platform.startswith(x) for x in supported)):
            notrun('not suitable for this OS: %s' % sys.platform)

def verify_cache_mode(supported_cache_modes=[]):
    if supported_cache_modes and (cachemode not in supported_cache_modes):
        notrun('not suitable for this cache mode: %s' % cachemode)

def verify_aio_mode(supported_aio_modes=[]):
    if supported_aio_modes and (aiomode not in supported_aio_modes):
        notrun('not suitable for this aio mode: %s' % aiomode)

def supports_quorum():
    return 'quorum' in qemu_img_pipe('--help')

def verify_quorum():
    '''Skip test suite if quorum support is not available'''
    if not supports_quorum():
        notrun('quorum support missing')

def qemu_pipe(*args):
    '''Run qemu with an option to print something and exit (e.g. a help option),
    and return its output'''
    args = [qemu_prog] + qemu_opts + list(args)
    subp = subprocess.Popen(args, stdout=subprocess.PIPE,
                            stderr=subprocess.STDOUT,
                            universal_newlines=True)
    exitcode = subp.wait()
    if exitcode < 0:
        sys.stderr.write('qemu received signal %i: %s\n' %
                         (-exitcode, ' '.join(args)))
    return subp.communicate()[0]

def supported_formats(read_only=False):
    '''Set 'read_only' to True to check ro-whitelist
       Otherwise, rw-whitelist is checked'''

    if not hasattr(supported_formats, "formats"):
        supported_formats.formats = {}

    if read_only not in supported_formats.formats:
        format_message = qemu_pipe("-drive", "format=help")
        line = 1 if read_only else 0
        supported_formats.formats[read_only] = \
            format_message.splitlines()[line].split(":")[1].split()

    return supported_formats.formats[read_only]

def skip_if_unsupported(required_formats=[], read_only=False):
    '''Skip Test Decorator
       Runs the test if all the required formats are whitelisted'''
    def skip_test_decorator(func):
        def func_wrapper(test_case: QMPTestCase, *args, **kwargs):
            if callable(required_formats):
                fmts = required_formats(test_case)
            else:
                fmts = required_formats

            usf_list = list(set(fmts) - set(supported_formats(read_only)))
            if usf_list:
                test_case.case_skip('{}: formats {} are not whitelisted'.format(
                    test_case, usf_list))
                return None
            else:
                return func(test_case, *args, **kwargs)
        return func_wrapper
    return skip_test_decorator

def skip_if_user_is_root(func):
    '''Skip Test Decorator
       Runs the test only without root permissions'''
    def func_wrapper(*args, **kwargs):
        if os.getuid() == 0:
            case_notrun('{}: cannot be run as root'.format(args[0]))
            return None
        else:
            return func(*args, **kwargs)
    return func_wrapper

def execute_unittest(output, verbosity, debug):
    runner = unittest.TextTestRunner(stream=output, descriptions=True,
                                     verbosity=verbosity)
    try:
        # unittest.main() will use sys.exit(); so expect a SystemExit
        # exception
        unittest.main(testRunner=runner)
    finally:
        if not debug:
            out = output.getvalue()
            out = re.sub(r'Ran (\d+) tests? in [\d.]+s', r'Ran \1 tests', out)

            # Hide skipped tests from the reference output
            out = re.sub(r'OK \(skipped=\d+\)', 'OK', out)
            out_first_line, out_rest = out.split('\n', 1)
            out = out_first_line.replace('s', '.') + '\n' + out_rest

            sys.stderr.write(out)

def execute_test(test_function=None,
                 supported_fmts=[],
                 supported_platforms=None,
                 supported_cache_modes=[], supported_aio_modes={},
                 unsupported_fmts=[], supported_protocols=[],
                 unsupported_protocols=[]):
    """Run either unittest or script-style tests."""

    # We are using TEST_DIR and QEMU_DEFAULT_MACHINE as proxies to
    # indicate that we're not being run via "check". There may be
    # other things set up by "check" that individual test cases rely
    # on.
    if test_dir is None or qemu_default_machine is None:
        sys.stderr.write('Please run this test via the "check" script\n')
        sys.exit(os.EX_USAGE)

    debug = '-d' in sys.argv
    verbosity = 1
    verify_image_format(supported_fmts, unsupported_fmts)
    verify_protocol(supported_protocols, unsupported_protocols)
    verify_platform(supported=supported_platforms)
    verify_cache_mode(supported_cache_modes)
    verify_aio_mode(supported_aio_modes)

    if debug:
        output = sys.stdout
        verbosity = 2
        sys.argv.remove('-d')
    else:
        # We need to filter out the time taken from the output so that
        # qemu-iotest can reliably diff the results against master output.
        output = io.StringIO()

    logging.basicConfig(level=(logging.DEBUG if debug else logging.WARN))

    if not test_function:
        execute_unittest(output, verbosity, debug)
    else:
        test_function()

def script_main(test_function, *args, **kwargs):
    """Run script-style tests outside of the unittest framework"""
    execute_test(test_function, *args, **kwargs)

def main(*args, **kwargs):
    """Run tests using the unittest framework"""
    execute_test(None, *args, **kwargs)