qemu/tests/vm/basevm.py

#
# VM testing base class
#
# Copyright 2017-2019 Red Hat Inc.
#
# Authors:
#  Fam Zheng <famz@redhat.com>
#  Gerd Hoffmann <kraxel@redhat.com>
#
# This code is licensed under the GPL version 2 or later.  See
# the COPYING file in the top-level directory.
#

import os
import re
import sys
import socket
import logging
import time
import datetime
import subprocess
import hashlib
import argparse
import atexit
import tempfile
import shutil
import multiprocessing
import traceback
import shlex
import json

from qemu.machine import QEMUMachine
from qemu.utils import get_info_usernet_hostfwd_port, kvm_available

SSH_KEY_FILE = os.path.join(os.path.dirname(__file__),
               "..", "keys", "id_rsa")
SSH_PUB_KEY_FILE = os.path.join(os.path.dirname(__file__),
                   "..", "keys", "id_rsa.pub")

# This is the standard configuration.
# Any or all of these can be overridden by
# passing in a config argument to the VM constructor.
DEFAULT_CONFIG = {
    'cpu'             : "max",
    'machine'         : 'pc',
    'guest_user'      : "qemu",
    'guest_pass'      : "qemupass",
    'root_user'       : "root",
    'root_pass'       : "qemupass",
    'ssh_key_file'    : SSH_KEY_FILE,
    'ssh_pub_key_file': SSH_PUB_KEY_FILE,
    'memory'          : "4G",
    'extra_args'      : [],
    'qemu_args'       : "",
    'dns'             : "",
    'ssh_port'        : 0,
    'install_cmds'    : "",
    'boot_dev_type'   : "block",
    'ssh_timeout'     : 1,
}
BOOT_DEVICE = {
    'block' :  "-drive file={},if=none,id=drive0,cache=writeback "\
               "-device virtio-blk,drive=drive0,bootindex=0",
    'scsi'  :  "-device virtio-scsi-device,id=scsi "\
               "-drive file={},format=raw,if=none,id=hd0 "\
               "-device scsi-hd,drive=hd0,bootindex=0",
}
class BaseVM(object):

    envvars = [
        "https_proxy",
        "http_proxy",
        "ftp_proxy",
        "no_proxy",
    ]

    # The script to run in the guest that builds QEMU
    BUILD_SCRIPT = ""
    # The guest name, to be overridden by subclasses
    name = "#base"
    # The guest architecture, to be overridden by subclasses
    arch = "#arch"
    # command to halt the guest, can be overridden by subclasses
    poweroff = "poweroff"
    # Time to wait for shutdown to finish.
    shutdown_timeout_default = 30
    # enable IPv6 networking
    ipv6 = True
    # This is the timeout on the wait for console bytes.
    socket_timeout = 120
    # Scale up some timeouts under TCG.
    # 4 is arbitrary, but greater than 2,
    # since we found we need to wait more than twice as long.
    tcg_timeout_multiplier = 4
    def __init__(self, args, config=None):
        self._guest = None
        self._genisoimage = args.genisoimage
        self._build_path = args.build_path
        self._efi_aarch64 = args.efi_aarch64
        self._source_path = args.source_path
        # Allow input config to override defaults.
        self._config = DEFAULT_CONFIG.copy()

        # 1GB per core, minimum of 4. This is only a default.
        mem = max(4, args.jobs)
        self._config['memory'] = f"{mem}G"

        if config != None:
            self._config.update(config)
        self.validate_ssh_keys()
        self._tmpdir = os.path.realpath(tempfile.mkdtemp(prefix="vm-test-",
                                                         suffix=".tmp",
                                                         dir="."))
        atexit.register(shutil.rmtree, self._tmpdir)
        # Copy the key files to a temporary directory.
        # Also chmod the key file to agree with ssh requirements.
        self._config['ssh_key'] = \
            open(self._config['ssh_key_file']).read().rstrip()
        self._config['ssh_pub_key'] = \
            open(self._config['ssh_pub_key_file']).read().rstrip()
        self._ssh_tmp_key_file = os.path.join(self._tmpdir, "id_rsa")
        open(self._ssh_tmp_key_file, "w").write(self._config['ssh_key'])
        subprocess.check_call(["chmod", "600", self._ssh_tmp_key_file])

        self._ssh_tmp_pub_key_file = os.path.join(self._tmpdir, "id_rsa.pub")
        open(self._ssh_tmp_pub_key_file,
             "w").write(self._config['ssh_pub_key'])

        self.debug = args.debug
        self._console_log_path = None
        if args.log_console:
                self._console_log_path = \
                         os.path.join(os.path.expanduser("~/.cache/qemu-vm"),
                                      "{}.install.log".format(self.name))
        self._stderr = sys.stderr
        self._devnull = open(os.devnull, "w")
        if self.debug:
            self._stdout = sys.stdout
        else:
            self._stdout = self._devnull
        netdev = "user,id=vnet,hostfwd=:127.0.0.1:{}-:22"
        self._args = [ \
            "-nodefaults", "-m", self._config['memory'],
            "-cpu", self._config['cpu'],
            "-netdev",
            netdev.format(self._config['ssh_port']) +
            (",ipv6=no" if not self.ipv6 else "") +
            (",dns=" + self._config['dns'] if self._config['dns'] else ""),
            "-device", "virtio-net-pci,netdev=vnet",
            "-vnc", "127.0.0.1:0,to=20"]
        if args.jobs and args.jobs > 1:
            self._args += ["-smp", "%d" % args.jobs]
        if kvm_available(self.arch):
            self._shutdown_timeout = self.shutdown_timeout_default
            self._args += ["-enable-kvm"]
        else:
            logging.info("KVM not available, not using -enable-kvm")
            self._shutdown_timeout = \
                self.shutdown_timeout_default * self.tcg_timeout_multiplier
        self._data_args = []

        if self._config['qemu_args'] != None:
            qemu_args = self._config['qemu_args']
            qemu_args = qemu_args.replace('\n',' ').replace('\r','')
            # shlex groups quoted arguments together
            # we need this to keep the quoted args together for when
            # the QEMU command is issued later.
            args = shlex.split(qemu_args)
            self._config['extra_args'] = []
            for arg in args:
                if arg:
                    # Preserve quotes around arguments.
                    # shlex above takes them out, so add them in.
                    if " " in arg:
                        arg = '"{}"'.format(arg)
                    self._config['extra_args'].append(arg)

    def validate_ssh_keys(self):
        """Check to see if the ssh key files exist."""
        if 'ssh_key_file' not in self._config or\
           not os.path.exists(self._config['ssh_key_file']):
            raise Exception("ssh key file not found.")
        if 'ssh_pub_key_file' not in self._config or\
           not os.path.exists(self._config['ssh_pub_key_file']):
               raise Exception("ssh pub key file not found.")

    def wait_boot(self, wait_string=None):
        """Wait for the standard string we expect
           on completion of a normal boot.
           The user can also choose to override with an
           alternate string to wait for."""
        if wait_string is None:
            if self.login_prompt is None:
                raise Exception("self.login_prompt not defined")
            wait_string = self.login_prompt
        # Intentionally bump up the default timeout under TCG,
        # since the console wait below takes longer.
        timeout = self.socket_timeout
        if not kvm_available(self.arch):
            timeout *= 8
        self.console_init(timeout=timeout)
        self.console_wait(wait_string)

    def _download_with_cache(self, url, sha256sum=None, sha512sum=None):
        def check_sha256sum(fname):
            if not sha256sum:
                return True
            checksum = subprocess.check_output(["sha256sum", fname]).split()[0]
            return sha256sum == checksum.decode("utf-8")

        def check_sha512sum(fname):
            if not sha512sum:
                return True
            checksum = subprocess.check_output(["sha512sum", fname]).split()[0]
            return sha512sum == checksum.decode("utf-8")

        cache_dir = os.path.expanduser("~/.cache/qemu-vm/download")
        if not os.path.exists(cache_dir):
            os.makedirs(cache_dir)
        fname = os.path.join(cache_dir,
                             hashlib.sha1(url.encode("utf-8")).hexdigest())
        if os.path.exists(fname) and check_sha256sum(fname) and check_sha512sum(fname):
            return fname
        logging.debug("Downloading %s to %s...", url, fname)
        subprocess.check_call(["wget", "-c", url, "-O", fname + ".download"],
                              stdout=self._stdout, stderr=self._stderr)
        os.rename(fname + ".download", fname)
        return fname

    def _ssh_do(self, user, cmd, check):
        ssh_cmd = ["ssh",
                   "-t",
                   "-o", "StrictHostKeyChecking=no",
                   "-o", "UserKnownHostsFile=" + os.devnull,
                   "-o",
                   "ConnectTimeout={}".format(self._config["ssh_timeout"]),
                   "-p", str(self.ssh_port), "-i", self._ssh_tmp_key_file,
                   "-o", "IdentitiesOnly=yes"]
        # If not in debug mode, set ssh to quiet mode to
        # avoid printing the results of commands.
        if not self.debug:
            ssh_cmd.append("-q")
        for var in self.envvars:
            ssh_cmd += ['-o', "SendEnv=%s" % var ]
        assert not isinstance(cmd, str)
        ssh_cmd += ["%s@127.0.0.1" % user] + list(cmd)
        logging.debug("ssh_cmd: %s", " ".join(ssh_cmd))
        r = subprocess.call(ssh_cmd)
        if check and r != 0:
            raise Exception("SSH command failed: %s" % cmd)
        return r

    def ssh(self, *cmd):
        return self._ssh_do(self._config["guest_user"], cmd, False)

    def ssh_root(self, *cmd):
        return self._ssh_do(self._config["root_user"], cmd, False)

    def ssh_check(self, *cmd):
        self._ssh_do(self._config["guest_user"], cmd, True)

    def ssh_root_check(self, *cmd):
        self._ssh_do(self._config["root_user"], cmd, True)

    def build_image(self, img):
        raise NotImplementedError

    def exec_qemu_img(self, *args):
        cmd = [os.environ.get("QEMU_IMG", "qemu-img")]
        cmd.extend(list(args))
        subprocess.check_call(cmd)

    def add_source_dir(self, src_dir):
        name = "data-" + hashlib.sha1(src_dir.encode("utf-8")).hexdigest()[:5]
        tarfile = os.path.join(self._tmpdir, name + ".tar")
        logging.debug("Creating archive %s for src_dir dir: %s", tarfile, src_dir)
        subprocess.check_call(["./scripts/archive-source.sh", tarfile],
                              cwd=src_dir, stdin=self._devnull,
                              stdout=self._stdout, stderr=self._stderr)
        self._data_args += ["-drive",
                            "file=%s,if=none,id=%s,cache=writeback,format=raw" % \
                                    (tarfile, name),
                            "-device",
                            "virtio-blk,drive=%s,serial=%s,bootindex=1" % (name, name)]

    def boot(self, img, extra_args=[]):
        boot_dev = BOOT_DEVICE[self._config['boot_dev_type']]
        boot_params = boot_dev.format(img)
        args = self._args + boot_params.split(' ')
        args += self._data_args + extra_args + self._config['extra_args']
        logging.debug("QEMU args: %s", " ".join(args))
        qemu_path = get_qemu_path(self.arch, self._build_path)

        # Since console_log_path is only set when the user provides the
        # log_console option, we will set drain_console=True so the
        # console is always drained.
        guest = QEMUMachine(binary=qemu_path, args=args,
                            console_log=self._console_log_path,
                            drain_console=True)
        guest.set_machine(self._config['machine'])
        guest.set_console()
        try:
            guest.launch()
        except:
            logging.error("Failed to launch QEMU, command line:")
            logging.error(" ".join([qemu_path] + args))
            logging.error("Log:")
            logging.error(guest.get_log())
            logging.error("QEMU version >= 2.10 is required")
            raise
        atexit.register(self.shutdown)
        self._guest = guest
        # Init console so we can start consuming the chars.
        self.console_init()
        usernet_info = guest.cmd("human-monitor-command",
                                 command_line="info usernet")
        self.ssh_port = get_info_usernet_hostfwd_port(usernet_info)
        if not self.ssh_port:
            raise Exception("Cannot find ssh port from 'info usernet':\n%s" % \
                            usernet_info)

    def console_init(self, timeout = None):
        if timeout == None:
            timeout = self.socket_timeout
        vm = self._guest
        vm.console_socket.settimeout(timeout)
        self.console_raw_path = os.path.join(vm._temp_dir,
                                             vm._name + "-console.raw")
        self.console_raw_file = open(self.console_raw_path, 'wb')

    def console_log(self, text):
        for line in re.split("[\r\n]", text):
            # filter out terminal escape sequences
            line = re.sub("\x1b\\[[0-9;?]*[a-zA-Z]", "", line)
            line = re.sub("\x1b\\([0-9;?]*[a-zA-Z]", "", line)
            # replace unprintable chars
            line = re.sub("\x1b", "<esc>", line)
            line = re.sub("[\x00-\x1f]", ".", line)
            line = re.sub("[\x80-\xff]", ".", line)
            if line == "":
                continue
            # log console line
            sys.stderr.write("con recv: %s\n" % line)

    def console_wait(self, expect, expectalt = None):
        vm = self._guest
        output = ""
        while True:
            try:
                chars = vm.console_socket.recv(1)
                if self.console_raw_file:
                    self.console_raw_file.write(chars)
                    self.console_raw_file.flush()
            except socket.timeout:
                sys.stderr.write("console: *** read timeout ***\n")
                sys.stderr.write("console: waiting for: '%s'\n" % expect)
                if not expectalt is None:
                    sys.stderr.write("console: waiting for: '%s' (alt)\n" % expectalt)
                sys.stderr.write("console: line buffer:\n")
                sys.stderr.write("\n")
                self.console_log(output.rstrip())
                sys.stderr.write("\n")
                raise
            output += chars.decode("latin1")
            if expect in output:
                break
            if not expectalt is None and expectalt in output:
                break
            if "\r" in output or "\n" in output:
                lines = re.split("[\r\n]", output)
                output = lines.pop()
                if self.debug:
                    self.console_log("\n".join(lines))
        if self.debug:
            self.console_log(output)
        if not expectalt is None and expectalt in output:
            return False
        return True

    def console_consume(self):
        vm = self._guest
        output = ""
        vm.console_socket.setblocking(0)
        while True:
            try:
                chars = vm.console_socket.recv(1)
            except:
                break
            output += chars.decode("latin1")
            if "\r" in output or "\n" in output:
                lines = re.split("[\r\n]", output)
                output = lines.pop()
                if self.debug:
                    self.console_log("\n".join(lines))
        if self.debug:
            self.console_log(output)
        vm.console_socket.setblocking(1)

    def console_send(self, command):
        vm = self._guest
        if self.debug:
            logline = re.sub("\n", "<enter>", command)
            logline = re.sub("[\x00-\x1f]", ".", logline)
            sys.stderr.write("con send: %s\n" % logline)
        for char in list(command):
            vm.console_socket.send(char.encode("utf-8"))
            time.sleep(0.01)

    def console_wait_send(self, wait, command):
        self.console_wait(wait)
        self.console_send(command)

    def console_ssh_init(self, prompt, user, pw):
        sshkey_cmd = "echo '%s' > .ssh/authorized_keys\n" \
                     % self._config['ssh_pub_key'].rstrip()
        self.console_wait_send("login:",    "%s\n" % user)
        self.console_wait_send("Password:", "%s\n" % pw)
        self.console_wait_send(prompt,      "mkdir .ssh\n")
        self.console_wait_send(prompt,      sshkey_cmd)
        self.console_wait_send(prompt,      "chmod 755 .ssh\n")
        self.console_wait_send(prompt,      "chmod 644 .ssh/authorized_keys\n")

    def console_sshd_config(self, prompt):
        self.console_wait(prompt)
        self.console_send("echo 'PermitRootLogin yes' >> /etc/ssh/sshd_config\n")
        for var in self.envvars:
            self.console_wait(prompt)
            self.console_send("echo 'AcceptEnv %s' >> /etc/ssh/sshd_config\n" % var)

    def print_step(self, text):
        sys.stderr.write("### %s ...\n" % text)

    def wait_ssh(self, wait_root=False, seconds=300, cmd="exit 0"):
        # Allow more time for VM to boot under TCG.
        if not kvm_available(self.arch):
            seconds *= self.tcg_timeout_multiplier
        starttime = datetime.datetime.now()
        endtime = starttime + datetime.timedelta(seconds=seconds)
        cmd_success = False
        while datetime.datetime.now() < endtime:
            if wait_root and self.ssh_root(cmd) == 0:
                cmd_success = True
                break
            elif self.ssh(cmd) == 0:
                cmd_success = True
                break
            seconds = (endtime - datetime.datetime.now()).total_seconds()
            logging.debug("%ds before timeout", seconds)
            time.sleep(1)
        if not cmd_success:
            raise Exception("Timeout while waiting for guest ssh")

    def shutdown(self):
        self._guest.shutdown(timeout=self._shutdown_timeout)

    def wait(self):
        self._guest.wait(timeout=self._shutdown_timeout)

    def graceful_shutdown(self):
        self.ssh_root(self.poweroff)
        self._guest.wait(timeout=self._shutdown_timeout)

    def qmp(self, *args, **kwargs):
        return self._guest.qmp(*args, **kwargs)

    def gen_cloud_init_iso(self):
        cidir = self._tmpdir
        mdata = open(os.path.join(cidir, "meta-data"), "w")
        name = self.name.replace(".","-")
        mdata.writelines(["instance-id: {}-vm-0\n".format(name),
                          "local-hostname: {}-guest\n".format(name)])
        mdata.close()
        udata = open(os.path.join(cidir, "user-data"), "w")
        print("guest user:pw {}:{}".format(self._config['guest_user'],
                                           self._config['guest_pass']))
        udata.writelines(["#cloud-config\n",
                          "chpasswd:\n",
                          "  list: |\n",
                          "    root:%s\n" % self._config['root_pass'],
                          "    %s:%s\n" % (self._config['guest_user'],
                                           self._config['guest_pass']),
                          "  expire: False\n",
                          "users:\n",
                          "  - name: %s\n" % self._config['guest_user'],
                          "    sudo: ALL=(ALL) NOPASSWD:ALL\n",
                          "    ssh-authorized-keys:\n",
                          "    - %s\n" % self._config['ssh_pub_key'],
                          "  - name: root\n",
                          "    ssh-authorized-keys:\n",
                          "    - %s\n" % self._config['ssh_pub_key'],
                          "locale: en_US.UTF-8\n"])
        proxy = os.environ.get("http_proxy")
        if not proxy is None:
            udata.writelines(["apt:\n",
                              "  proxy: %s" % proxy])
        udata.close()
        subprocess.check_call([self._genisoimage, "-output", "cloud-init.iso",
                               "-volid", "cidata", "-joliet", "-rock",
                               "user-data", "meta-data"],
                              cwd=cidir,
                              stdin=self._devnull, stdout=self._stdout,
                              stderr=self._stdout)
        return os.path.join(cidir, "cloud-init.iso")

    def get_qemu_packages_from_lcitool_json(self, json_path=None):
        """Parse a lcitool variables json file and return the PKGS list."""
        if json_path is None:
            json_path = os.path.join(
                os.path.dirname(__file__), "generated", self.name + ".json"
            )
        with open(json_path, "r") as fh:
            return json.load(fh)["pkgs"]


def get_qemu_path(arch, build_path=None):
    """Fetch the path to the qemu binary."""
    # If QEMU environment variable set, it takes precedence
    if "QEMU" in os.environ:
        qemu_path = os.environ["QEMU"]
    elif build_path:
        qemu_path = os.path.join(build_path, arch + "-softmmu")
        qemu_path = os.path.join(qemu_path, "qemu-system-" + arch)
    else:
        # Default is to use system path for qemu.
        qemu_path = "qemu-system-" + arch
    return qemu_path

def get_qemu_version(qemu_path):
    """Get the version number from the current QEMU,
       and return the major number."""
    output = subprocess.check_output([qemu_path, '--version'])
    version_line = output.decode("utf-8")
    version_num = re.split(r' |\(', version_line)[3].split('.')[0]
    return int(version_num)

def parse_config(config, args):
    """ Parse yaml config and populate our config structure.
        The yaml config allows the user to override the
        defaults for VM parameters.  In many cases these
        defaults can be overridden without rebuilding the VM."""
    if args.config:
        config_file = args.config
    elif 'QEMU_CONFIG' in os.environ:
        config_file = os.environ['QEMU_CONFIG']
    else:
        return config
    if not os.path.exists(config_file):
        raise Exception("config file {} does not exist".format(config_file))
    # We gracefully handle importing the yaml module
    # since it might not be installed.
    # If we are here it means the user supplied a .yml file,
    # so if the yaml module is not installed we will exit with error.
    try:
        import yaml
    except ImportError:
        print("The python3-yaml package is needed "\
              "to support config.yaml files")
        # Instead of raising an exception we exit to avoid
        # a raft of messy (expected) errors to stdout.
        exit(1)
    with open(config_file) as f:
        yaml_dict = yaml.safe_load(f)

    if 'qemu-conf' in yaml_dict:
        config.update(yaml_dict['qemu-conf'])
    else:
        raise Exception("config file {} is not valid"\
                        " missing qemu-conf".format(config_file))
    return config

def parse_args(vmcls):

    def get_default_jobs():
        if multiprocessing.cpu_count() > 1:
            if kvm_available(vmcls.arch):
                return multiprocessing.cpu_count() // 2
            elif os.uname().machine == "x86_64" and \
                 vmcls.arch in ["aarch64", "x86_64", "i386"]:
                # MTTCG is available on these arches and we can allow
                # more cores. but only up to a reasonable limit. User
                # can always override these limits with --jobs.
                return min(multiprocessing.cpu_count() // 2, 8)
        return 1

    parser = argparse.ArgumentParser(
        formatter_class=argparse.ArgumentDefaultsHelpFormatter,
        description="Utility for provisioning VMs and running builds",
        epilog="""Remaining arguments are passed to the command.
        Exit codes: 0 = success, 1 = command line error,
        2 = environment initialization failed,
        3 = test command failed""")
    parser.add_argument("--debug", "-D", action="store_true",
                        help="enable debug output")
    parser.add_argument("--image", "-i", default="%s.img" % vmcls.name,
                        help="image file name")
    parser.add_argument("--force", "-f", action="store_true",
                        help="force build image even if image exists")
    parser.add_argument("--jobs", type=int, default=get_default_jobs(),
                        help="number of virtual CPUs")
    parser.add_argument("--verbose", "-V", action="store_true",
                        help="Pass V=1 to builds within the guest")
    parser.add_argument("--build-image", "-b", action="store_true",
                        help="build image")
    parser.add_argument("--build-qemu",
                        help="build QEMU from source in guest")
    parser.add_argument("--build-target",
                        help="QEMU build target", default="check")
    parser.add_argument("--build-path", default=None,
                        help="Path of build directory, "\
                        "for using build tree QEMU binary. ")
    parser.add_argument("--source-path", default=None,
                        help="Path of source directory, "\
                        "for finding additional files. ")
    parser.add_argument("--interactive", "-I", action="store_true",
                        help="Interactively run command")
    parser.add_argument("--snapshot", "-s", action="store_true",
                        help="run tests with a snapshot")
    parser.add_argument("--genisoimage", default="genisoimage",
                        help="iso imaging tool")
    parser.add_argument("--config", "-c", default=None,
                        help="Provide config yaml for configuration. "\
                        "See config_example.yaml for example.")
    parser.add_argument("--efi-aarch64",
                        default="/usr/share/qemu-efi-aarch64/QEMU_EFI.fd",
                        help="Path to efi image for aarch64 VMs.")
    parser.add_argument("--log-console", action="store_true",
                        help="Log console to file.")
    parser.add_argument("commands", nargs="*", help="""Remaining
        commands after -- are passed to command inside the VM""")

    return parser.parse_args()

def main(vmcls, config=None):
    try:
        if config == None:
            config = DEFAULT_CONFIG
        args = parse_args(vmcls)
        if not args.commands and not args.build_qemu and not args.build_image:
            print("Nothing to do?")
            return 1
        config = parse_config(config, args)
        logging.basicConfig(level=(logging.DEBUG if args.debug
                                   else logging.WARN))
        vm = vmcls(args, config=config)
        if args.build_image:
            if os.path.exists(args.image) and not args.force:
                sys.stderr.writelines(["Image file exists: %s\n" % args.image,
                                      "Use --force option to overwrite\n"])
                return 1
            return vm.build_image(args.image)
        if args.build_qemu:
            vm.add_source_dir(args.build_qemu)
            cmd = [vm.BUILD_SCRIPT.format(
                   configure_opts = " ".join(args.commands),
                   jobs=int(args.jobs),
                   target=args.build_target,
                   verbose = "V=1" if args.verbose else "")]
        else:
            cmd = args.commands
        img = args.image
        if args.snapshot:
            img += ",snapshot=on"
        vm.boot(img)
        vm.wait_ssh()
    except Exception as e:
        if isinstance(e, SystemExit) and e.code == 0:
            return 0
        sys.stderr.write("Failed to prepare guest environment\n")
        traceback.print_exc()
        return 2

    exitcode = 0
    if vm.ssh(*cmd) != 0:
        exitcode = 3
    if args.interactive:
        vm.ssh()

    if not args.snapshot:
        vm.graceful_shutdown()

    return exitcode