qemu.py

# SPDX-License-Identifier: LGPL-2.1+

import asyncio
import base64
import contextlib
import enum
import errno
import fcntl
import hashlib
import json
import logging
import os
import random
import shutil
import socket
import struct
import subprocess
import sys
import tempfile
import uuid
from collections.abc import Iterator
from pathlib import Path
from typing import NamedTuple, Optional

from mkosi.config import (
    Args,
    Config,
    ConfigFeature,
    Network,
    OutputFormat,
    QemuDrive,
    QemuFirmware,
    QemuVsockCID,
    format_bytes,
    systemd_tool_version,
    want_selinux_relabel,
)
from mkosi.log import ARG_DEBUG, die
from mkosi.partition import finalize_root, find_partitions
from mkosi.run import AsyncioThread, find_binary, fork_and_wait, run, spawn
from mkosi.sandbox import Mount
from mkosi.tree import copy_tree, rmtree
from mkosi.types import PathString
from mkosi.user import INVOKING_USER, become_root
from mkosi.util import StrEnum, flatten, flock, flock_or_die
from mkosi.versioncomp import GenericVersion

QEMU_KVM_DEVICE_VERSION = GenericVersion("9.0")
VHOST_VSOCK_SET_GUEST_CID = 0x4008af60


class QemuDeviceNode(StrEnum):
    kvm = enum.auto()
    vhost_vsock = enum.auto()

    def device(self) -> Path:
        return Path("/dev") / str(self)

    def description(self) -> str:
        return {
            QemuDeviceNode.kvm: "KVM acceleration",
            QemuDeviceNode.vhost_vsock: "a VSock device",
        }[self]

    def feature(self, config: Config) -> ConfigFeature:
        return {
            QemuDeviceNode.kvm: config.qemu_kvm,
            QemuDeviceNode.vhost_vsock: config.qemu_vsock,
        }[self]

    def open(self) -> int:
        return os.open(self.device(), os.O_RDWR|os.O_CLOEXEC|os.O_NONBLOCK)

    def available(self, log: bool = False) -> bool:
        try:
            os.close(self.open())
        except OSError as e:
            if e.errno not in (errno.ENOENT, errno.ENODEV, errno.EPERM, errno.EACCES):
                raise e

            if log and e.errno in (errno.ENOENT, errno.ENODEV):
                logging.warning(f"{self.device()} not found. Not adding {self.description()} to the virtual machine.")

            if log and e.errno in (errno.EPERM, errno.EACCES):
                logging.warning(
                    f"Permission denied to access {self.device()}. "
                    f"Not adding {self.description()} to the virtual machine. "
                    "(Maybe a kernel module could not be loaded?)"
                )

            return False

        return True


def hash_output(config: Config) -> "hashlib._Hash":
    p = os.fspath(config.output_dir_or_cwd() / config.output)
    return hashlib.sha256(p.encode())


def hash_to_vsock_cid(hash: "hashlib._Hash") -> int:
    cid = int.from_bytes(hash.digest()[:4], byteorder='little')
    # Make sure we don't return any of the well-known CIDs.
    return max(3, min(cid, 0xFFFFFFFF - 1))


def vsock_cid_in_use(vfd: int, cid: int) -> bool:
    try:
        fcntl.ioctl(vfd, VHOST_VSOCK_SET_GUEST_CID, struct.pack("=Q", cid))
    except OSError as e:
        if e.errno != errno.EADDRINUSE:
            raise

        return True

    return False


def find_unused_vsock_cid(config: Config, vfd: int) -> int:
    hash = hash_output(config)

    for i in range(64):
        cid = hash_to_vsock_cid(hash)

        if not vsock_cid_in_use(vfd, cid):
            return cid

        hash.update(i.to_bytes(length=4, byteorder='little'))

    for i in range(64):
        cid = random.randint(0, 0xFFFFFFFF - 1)

        if not vsock_cid_in_use(vfd, cid):
            return cid

    die("Failed to find an unused VSock connection ID")


class KernelType(StrEnum):
    pe      = enum.auto()
    uki     = enum.auto()
    unknown = enum.auto()

    @classmethod
    def identify(cls, config: Config, path: Path) -> "KernelType":
        if not find_binary("bootctl", root=config.tools()):
            logging.warning("bootctl is not installed, assuming 'unknown' kernel type")
            return KernelType.unknown

        if systemd_tool_version(config, "bootctl") < 253:
            logging.warning("bootctl doesn't know kernel-identify verb, assuming 'unknown' kernel type")
            return KernelType.unknown

        type = run(
            ["bootctl", "kernel-identify", path],
            stdout=subprocess.PIPE,
            sandbox=config.sandbox(mounts=[Mount(path, path, ro=True)]),
        ).stdout.strip()

        try:
            return cls(type)
        except ValueError:
            logging.warning(f"Unknown kernel type '{type}', assuming 'unknown'")
            return KernelType.unknown


def find_qemu_binary(config: Config) -> str:
    binaries = [f"qemu-system-{config.architecture.to_qemu()}"]
    binaries += ["qemu", "qemu-kvm"] if config.architecture.is_native() else []
    for binary in binaries:
        if find_binary(binary, root=config.tools()) is not None:
            return binary

    die("Couldn't find QEMU/KVM binary")


class OvmfConfig(NamedTuple):
    description: Path
    firmware: Path
    format: str
    vars: Path
    vars_format: str


def find_ovmf_firmware(config: Config, firmware: QemuFirmware) -> Optional[OvmfConfig]:
    if not firmware.is_uefi():
        return None

    desc = flatten(
        p.glob("*")
        for p in (
            config.tools() / "etc/qemu/firmware",
            config.tools() / "usr/share/qemu/firmware",
        )
    )

    arch = config.architecture.to_qemu()
    machine = config.architecture.default_qemu_machine()

    for p in sorted(desc):
        if p.is_dir():
            continue

        j = json.loads(p.read_text())

        if "uefi" not in j["interface-types"]:
            logging.debug(f"{p.name} firmware description does not target UEFI, skipping")
            continue

        for target in j["targets"]:
            if target["architecture"] != arch:
                continue

            # We cannot use fnmatch as for example our default machine for x86-64 is q35 and the firmware description
            # lists "pc-q35-*" so we use a substring check instead.
            if any(machine in glob for glob in target["machines"]):
                break
        else:
            logging.debug(
                f"{p.name} firmware description does not target architecture {arch} or machine {machine}, skipping"
            )
            continue

        if firmware == QemuFirmware.uefi_secure_boot and "secure-boot" not in j["features"]:
            logging.debug(f"{p.name} firmware description does not include secure boot, skipping")
            continue

        if firmware != QemuFirmware.uefi_secure_boot and "secure-boot" in j["features"]:
            logging.debug(f"{p.name} firmware description includes secure boot, skipping")
            continue

        if config.qemu_firmware_variables == Path("microsoft") and "enrolled-keys" not in j["features"]:
            logging.debug(f"{p.name} firmware description does not have enrolled Microsoft keys, skipping")
            continue

        if config.qemu_firmware_variables != Path("microsoft") and "enrolled-keys" in j["features"]:
            logging.debug(f"{p.name} firmware description has enrolled Microsoft keys, skipping")
            continue

        logging.debug(f"Using {p.name} firmware description")

        return OvmfConfig(
            description=Path("/") / p.relative_to(config.tools()),
            firmware=Path(j["mapping"]["executable"]["filename"]),
            format=j["mapping"]["executable"]["format"],
            vars=Path(j["mapping"]["nvram-template"]["filename"]),
            vars_format=j["mapping"]["nvram-template"]["format"],
        )

    die("Couldn't find matching OVMF UEFI firmware description")


@contextlib.contextmanager
def start_swtpm(config: Config) -> Iterator[Path]:
    with tempfile.TemporaryDirectory(prefix="mkosi-swtpm") as state:
        # swtpm_setup is noisy and doesn't have a --quiet option so we pipe it's stdout to /dev/null.
        run(["swtpm_setup", "--tpm-state", state, "--tpm2", "--pcr-banks", "sha256", "--config", "/dev/null"],
            sandbox=config.sandbox(mounts=[Mount(state, state)]),
            stdout=None if ARG_DEBUG.get() else subprocess.DEVNULL)

        cmdline = ["swtpm", "socket", "--tpm2", "--tpmstate", f"dir={state}"]

        # We create the socket ourselves and pass the fd to swtpm to avoid race conditions where we start qemu before
        # swtpm has had the chance to create the socket (or where we try to chown it first).
        with socket.socket(socket.AF_UNIX, socket.SOCK_STREAM) as sock:
            path = Path(state) / Path("sock")
            sock.bind(os.fspath(path))
            sock.listen()

            cmdline += ["--ctrl", f"type=unixio,fd={sock.fileno()}"]

            with spawn(
                cmdline,
                pass_fds=(sock.fileno(),),
                sandbox=config.sandbox(mounts=[Mount(state, state)]),
            ) as proc:
                yield path
                proc.terminate()


def find_virtiofsd(*, tools: Path = Path("/")) -> Optional[Path]:
    if p := find_binary("virtiofsd", root=tools):
        return p

    if (p := tools / "usr/libexec/virtiofsd").exists():
        return Path("/") / p.relative_to(tools)

    if (p := tools / "usr/lib/virtiofsd").exists():
        return Path("/") / p.relative_to(tools)

    return None


@contextlib.contextmanager
def start_virtiofsd(config: Config, directory: Path, *, uidmap: bool) -> Iterator[Path]:
    virtiofsd = find_virtiofsd(tools=config.tools())
    if virtiofsd is None:
        die("virtiofsd must be installed to boot directory images or use RuntimeTrees= with mkosi qemu")

    cmdline: list[PathString] = [
        virtiofsd,
        "--shared-dir", directory,
        "--xattr",
        # qemu's client doesn't seem to support announcing submounts so disable the feature to avoid the warning.
        "--no-announce-submounts",
        "--sandbox=chroot",
        "--cache=always",
        f"--inode-file-handles={'prefer' if os.getuid() == 0 and not uidmap else 'never'}",
    ]

    if not uidmap and want_selinux_relabel(config, directory, fatal=False):
        cmdline += ["--security-label"]

    # We create the socket ourselves and pass the fd to virtiofsd to avoid race conditions where we start qemu
    # before virtiofsd has had the chance to create the socket (or where we try to chown it first).
    with (
        tempfile.TemporaryDirectory(prefix="mkosi-virtiofsd") as context,
        socket.socket(socket.AF_UNIX, socket.SOCK_STREAM) as sock,
    ):
        # Make sure virtiofsd can access the socket in this directory.
        os.chown(context, INVOKING_USER.uid, INVOKING_USER.gid)

        # Make sure we can use the socket name as a unique identifier for the fs as well but make sure it's not too
        # long as virtiofs tag names are limited to 36 bytes.
        path = Path(context) / f"sock-{uuid.uuid4().hex}"[:35]
        sock.bind(os.fspath(path))
        sock.listen()

        # Make sure virtiofsd can connect to the socket.
        os.chown(path, INVOKING_USER.uid, INVOKING_USER.gid)

        cmdline += ["--fd", str(sock.fileno())]

        with spawn(
            cmdline,
            pass_fds=(sock.fileno(),),
            # When not invoked as root, bubblewrap will automatically map the current uid/gid to the requested uid/gid
            # in the user namespace it spawns, so by specifying --uid 0 --gid 0 we'll get a userns with the current
            # uid/gid mapped to root in the userns. --cap-add=all is required to make virtiofsd work. Since it drops
            # capabilities itself, we don't bother figuring out the exact set of capabilities it needs.
            user=INVOKING_USER.uid if uidmap else None,
            group=INVOKING_USER.gid if uidmap else None,
            preexec_fn=become_root if not uidmap else None,
            sandbox=config.sandbox(
                mounts=[Mount(directory, directory)],
                options=["--uid", "0", "--gid", "0", "--cap-add", "all"],
            ),
        ) as proc:
            yield path
            proc.terminate()


@contextlib.contextmanager
def vsock_notify_handler() -> Iterator[tuple[str, dict[str, str]]]:
    """
    This yields a vsock address and a dict that will be filled in with the notifications from the VM. The
    dict should only be accessed after the context manager has been finalized.
    """
    with socket.socket(socket.AF_VSOCK, socket.SOCK_STREAM) as vsock:
        vsock.bind((socket.VMADDR_CID_ANY, socket.VMADDR_PORT_ANY))
        vsock.listen()
        vsock.setblocking(False)

        num_messages = 0
        num_bytes = 0
        messages = {}

        async def notify() -> None:
            nonlocal num_messages
            nonlocal num_bytes
            loop = asyncio.get_running_loop()

            while True:
                s, _ = await loop.sock_accept(vsock)

                num_messages += 1

                with s:
                    data = []
                    try:
                        while (buf := await loop.sock_recv(s, 4096)):
                            data.append(buf)
                    except ConnectionResetError:
                        logging.debug("vsock notify listener connection reset by peer")

                for msg in b"".join(data).decode().split("\n"):
                    if not msg:
                        continue

                    num_bytes += len(msg)
                    k, _, v = msg.partition("=")
                    messages[k] = v

        with AsyncioThread(notify()):
            yield f"vsock-stream:{socket.VMADDR_CID_HOST}:{vsock.getsockname()[1]}", messages

        logging.debug(f"Received {num_messages} notify messages totalling {format_bytes(num_bytes)} bytes")
        for k, v in messages.items():
            logging.debug(f"- {k}={v}")


@contextlib.contextmanager
def copy_ephemeral(config: Config, src: Path) -> Iterator[Path]:
    if not config.ephemeral or config.output_format in (OutputFormat.cpio, OutputFormat.uki):
        with flock_or_die(src):
            yield src

        return

    src = src.resolve()
    # tempfile doesn't provide an API to get a random filename in an arbitrary directory so we do this
    # instead. Limit the size to 16 characters as the output name might be used in a unix socket path by vmspawn and
    # needs to fit in 108 characters.
    tmp = src.parent / f"{src.name}-{uuid.uuid4().hex[:16]}"

    try:
        def copy() -> None:
            if config.output_format == OutputFormat.directory:
                become_root()

            copy_tree(
                src, tmp,
                preserve=config.output_format == OutputFormat.directory,
                use_subvolumes=config.use_subvolumes,
                tools=config.tools(),
                sandbox=config.sandbox,
            )

        with flock(src):
            fork_and_wait(copy)
        yield tmp
    finally:
        def rm() -> None:
            if config.output_format == OutputFormat.directory:
                become_root()

            rmtree(tmp, tools=config.tools(), sandbox=config.sandbox)

        fork_and_wait(rm)


def qemu_version(config: Config) -> GenericVersion:
    return GenericVersion(run([find_qemu_binary(config), "--version"],
                              stdout=subprocess.PIPE, sandbox=config.sandbox()).stdout.split()[3])


def want_scratch(config: Config) -> bool:
    return config.runtime_scratch == ConfigFeature.enabled or (
        config.runtime_scratch == ConfigFeature.auto and
        find_binary(f"mkfs.{config.distribution.filesystem()}", root=config.tools()) is not None
    )


@contextlib.contextmanager
def generate_scratch_fs(config: Config) -> Iterator[Path]:
    with tempfile.NamedTemporaryFile(dir="/var/tmp", prefix="mkosi-scratch") as scratch:
        scratch.truncate(1024**4)
        fs = config.distribution.filesystem()
        extra = config.environment.get(f"SYSTEMD_REPART_MKFS_OPTIONS_{fs.upper()}", "")
        run(
            [f"mkfs.{fs}", "-L", "scratch", *extra.split(), scratch.name],
            stdout=subprocess.DEVNULL,
            sandbox=config.sandbox(mounts=[Mount(scratch.name, scratch.name)]),
        )
        yield Path(scratch.name)


def finalize_qemu_firmware(config: Config, kernel: Optional[Path]) -> QemuFirmware:
    if config.qemu_firmware == QemuFirmware.auto:
        if kernel:
            return (
                QemuFirmware.uefi_secure_boot
                if KernelType.identify(config, kernel) != KernelType.unknown
                else QemuFirmware.linux
            )
        elif (
            config.output_format in (OutputFormat.cpio, OutputFormat.directory) or
            config.architecture.to_efi() is None
        ):
            return QemuFirmware.linux
        else:
            return QemuFirmware.uefi_secure_boot
    else:
        return config.qemu_firmware


def finalize_firmware_variables(config: Config, ovmf: OvmfConfig, stack: contextlib.ExitStack) -> tuple[Path, str]:
    ovmf_vars = stack.enter_context(tempfile.NamedTemporaryFile(prefix="mkosi-ovmf-vars"))
    if config.qemu_firmware_variables in (None, Path("custom"), Path("microsoft")):
        ovmf_vars_format = ovmf.vars_format
    else:
        ovmf_vars_format = "raw"

    if config.qemu_firmware_variables == Path("custom"):
        assert config.secure_boot_certificate
        run(
            [
                "virt-fw-vars",
                "--input", ovmf.vars,
                "--output", ovmf_vars.name,
                "--enroll-cert", config.secure_boot_certificate,
                "--add-db", "OvmfEnrollDefaultKeys", config.secure_boot_certificate,
                "--no-microsoft",
                "--secure-boot",
                "--loglevel", "WARNING",
            ],
            sandbox=config.sandbox(
                mounts=[
                    Mount(ovmf_vars.name, ovmf_vars.name),
                    Mount(config.secure_boot_certificate, config.secure_boot_certificate, ro=True),
                ],
            ),
        )
    else:
        vars = (
            config.tools() / ovmf.vars.relative_to("/")
            if config.qemu_firmware_variables == Path("microsoft") or not config.qemu_firmware_variables
            else config.qemu_firmware_variables
        )
        shutil.copy2(vars, Path(ovmf_vars.name))

    return Path(ovmf_vars.name), ovmf_vars_format


def apply_runtime_size(config: Config, image: Path) -> None:
    if config.output_format != OutputFormat.disk or not config.runtime_size:
        return

    run(
        [
            "systemd-repart",
            "--definitions", "",
            "--no-pager",
            f"--size={config.runtime_size}",
            "--pretty=no",
            "--offline=yes",
            image,
        ],
        sandbox=config.sandbox(mounts=[Mount(image, image)]),
    )


@contextlib.contextmanager
def finalize_drive(drive: QemuDrive) -> Iterator[Path]:
    with tempfile.NamedTemporaryFile(dir=drive.directory or "/var/tmp", prefix=f"mkosi-drive-{drive.id}") as file:
        file.truncate(drive.size)
        yield Path(file.name)


@contextlib.contextmanager
def finalize_state(config: Config, cid: int) -> Iterator[None]:
    (INVOKING_USER.runtime_dir() / "machine").mkdir(parents=True, exist_ok=True)

    if INVOKING_USER.is_regular_user():
        os.chown(INVOKING_USER.runtime_dir(), INVOKING_USER.uid, INVOKING_USER.gid)
        os.chown(INVOKING_USER.runtime_dir() / "machine", INVOKING_USER.uid, INVOKING_USER.gid)

    with flock(INVOKING_USER.runtime_dir() / "machine"):
        if (p := INVOKING_USER.runtime_dir() / "machine" / f"{config.machine_or_name()}.json").exists():
            die(f"Another virtual machine named {config.machine_or_name()} is already running",
                hint="Use --machine to specify a different virtual machine name")

        p.write_text(
            json.dumps(
                {
                    "Machine": config.machine_or_name(),
                    "ProxyCommand": f"socat - VSOCK-CONNECT:{cid}:%p",
                    "SshKey": os.fspath(config.ssh_key) if config.ssh_key else None,
                },
                sort_keys=True,
                indent=4,
            )
        )

        if INVOKING_USER.is_regular_user():
            os.chown(p, INVOKING_USER.uid, INVOKING_USER.gid)

    try:
        yield
    finally:
        with flock(INVOKING_USER.runtime_dir() / "machine"):
            p.unlink(missing_ok=True)


def allocate_scope(config: Config, pid: int) -> None:
    if os.getuid() != 0 and "DBUS_SESSION_BUS_ADDRESS" not in os.environ:
        return

    if (
        os.getuid() == 0 and
        "DBUS_SYSTEM_ADDRESS" not in os.environ and
        not Path("/run/dbus/system_bus_socket").exists()
    ):
        return

    name = config.machine_or_name().replace("_", "-")

    scope = run(
        ["systemd-escape", "--mangle", f"{name}.scope"],
        stdout=subprocess.PIPE,
        foreground=False,
    ).stdout.strip()

    run(
        [
            "busctl",
            "call",
            "--system" if os.getuid() == 0 else "--user",
            "--quiet",
            "org.freedesktop.systemd1",
            "/org/freedesktop/systemd1",
            "org.freedesktop.systemd1.Manager",
            "StartTransientUnit",
            "ssa(sv)a(sa(sv))",
            scope,
            "fail",
            "4",
            "Description", "s", f"mkosi Virtual Machine {name}",
            "CollectMode", "s", "inactive-or-failed",
            "PIDs", "au", "1", str(pid),
            "AddRef", "b", "1",
            "0",
        ],
        foreground=False,
        env=os.environ | config.environment,
        sandbox=config.sandbox(relaxed=True),
    )


def register_machine(config: Config, pid: int, fname: Path) -> None:
    if (
        os.getuid() != 0 or
        ("DBUS_SYSTEM_ADDRESS" not in os.environ and not Path("/run/dbus/system_bus_socket").exists())
    ):
        return

    run(
        [
            "busctl",
            "call",
            "--quiet",
            "org.freedesktop.machine1",
            "/org/freedesktop/machine1",
            "org.freedesktop.machine1.Manager",
            "RegisterMachine",
            "sayssus",
            config.machine_or_name().replace("_", "-"),
            "0",
            "mkosi",
            "vm",
            str(pid),
            fname if fname.is_dir() else "",
        ],
        foreground=False,
        env=os.environ | config.environment,
        sandbox=config.sandbox(relaxed=True),
    )


def run_qemu(args: Args, config: Config) -> None:
    if config.output_format not in (
        OutputFormat.disk,
        OutputFormat.cpio,
        OutputFormat.uki,
        OutputFormat.esp,
        OutputFormat.directory,
    ):
        die(f"{config.output_format} images cannot be booted in qemu")

    if (
        config.output_format in (OutputFormat.cpio, OutputFormat.uki, OutputFormat.esp) and
        config.qemu_firmware not in (QemuFirmware.auto, QemuFirmware.linux) and
        not config.qemu_firmware.is_uefi()
    ):
        die(f"{config.output_format} images cannot be booted with the '{config.qemu_firmware}' firmware")

    if config.runtime_trees and config.qemu_firmware == QemuFirmware.bios:
        die("RuntimeTrees= cannot be used when booting in BIOS firmware")

    if config.qemu_kvm == ConfigFeature.enabled and not config.architecture.is_native():
        die(f"KVM acceleration requested but {config.architecture} does not match the native host architecture")

    if config.qemu_firmware_variables == Path("custom") and not config.secure_boot_certificate:
        die("SecureBootCertificate= must be configured to use QemuFirmwareVariables=custom")

    # After we unshare the user namespace to sandbox qemu, we might not have access to /dev/kvm or related device nodes
    # anymore as access to these might be gated behind the kvm group and we won't be part of the kvm group anymore
    # after unsharing the user namespace. To get around this, open all those device nodes early can pass them as file
    # descriptors to qemu later. Note that we can't pass the kvm file descriptor to qemu until version 9.0.
    qemu_device_fds = {
        d: d.open()
        for d in QemuDeviceNode
        if d.feature(config) != ConfigFeature.disabled and d.available(log=True)
    }

    have_kvm = ((qemu_version(config) < QEMU_KVM_DEVICE_VERSION and QemuDeviceNode.kvm.available()) or
                (qemu_version(config) >= QEMU_KVM_DEVICE_VERSION and QemuDeviceNode.kvm in qemu_device_fds))
    if config.qemu_kvm == ConfigFeature.enabled and not have_kvm:
        die("KVM acceleration requested but cannot access /dev/kvm")

    if config.qemu_vsock == ConfigFeature.enabled and QemuDeviceNode.vhost_vsock not in qemu_device_fds:
        die("VSock requested but cannot access /dev/vhost-vsock")

    if config.qemu_kernel:
        kernel = config.qemu_kernel
    elif "-kernel" in args.cmdline:
        kernel = Path(args.cmdline[args.cmdline.index("-kernel") + 1])
    else:
        kernel = None

    if config.output_format in (OutputFormat.uki, OutputFormat.esp) and kernel:
        logging.warning(
            f"Booting UKI output, kernel {kernel} configured with QemuKernel= or passed with -kernel will not be used"
        )
        kernel = None

    if kernel and not kernel.exists():
        die(f"Kernel not found at {kernel}")

    firmware = finalize_qemu_firmware(config, kernel)

    if (
        not kernel and
        (
            firmware == QemuFirmware.linux or
            config.output_format in (OutputFormat.cpio, OutputFormat.directory, OutputFormat.uki)
        )
    ):
        if firmware.is_uefi():
            name = config.output if config.output_format == OutputFormat.uki else config.output_split_uki
            kernel = config.output_dir_or_cwd() / name
        else:
            kernel = config.output_dir_or_cwd() / config.output_split_kernel
        if not kernel.exists():
            die(
                f"Kernel or UKI not found at {kernel}, please install a kernel in the image "
                "or provide a -kernel argument to mkosi qemu"
            )

    ovmf = find_ovmf_firmware(config, firmware)

    # A shared memory backend might increase ram usage so only add one if actually necessary for virtiofsd.
    shm = []
    if config.runtime_trees or config.output_format == OutputFormat.directory:
        shm = ["-object", f"memory-backend-memfd,id=mem,size={config.qemu_mem // 1024**2}M,share=on"]

    machine = f"type={config.architecture.default_qemu_machine()}"
    if firmware.is_uefi() and config.architecture.supports_smm():
        machine += f",smm={'on' if firmware == QemuFirmware.uefi_secure_boot else 'off'}"
    if shm:
        machine += ",memory-backend=mem"

    cmdline: list[PathString] = [
        find_qemu_binary(config),
        "-machine", machine,
        "-smp", str(config.qemu_smp),
        "-m", f"{config.qemu_mem // 1024**2}M",
        "-object", "rng-random,filename=/dev/urandom,id=rng0",
        "-device", "virtio-rng-pci,rng=rng0,id=rng-device0",
        "-no-user-config",
        *shm,
    ]

    if config.runtime_network == Network.user:
        cmdline += ["-nic", f"user,model={config.architecture.default_qemu_nic_model()}"]
    elif config.runtime_network == Network.interface:
        if os.getuid() != 0:
            die("RuntimeNetwork=interface requires root privileges")

        cmdline += ["-nic", "tap,script=no,model=virtio-net-pci"]
    elif config.runtime_network == Network.none:
        cmdline += ["-nic", "none"]

    if config.qemu_kvm != ConfigFeature.disabled and have_kvm and config.architecture.can_kvm():
        accel = "kvm"
        if qemu_version(config) >= QEMU_KVM_DEVICE_VERSION:
            cmdline += ["--add-fd", f"fd={qemu_device_fds[QemuDeviceNode.kvm]},set=1,opaque=/dev/kvm"]
            accel += ",device=/dev/fdset/1"
    else:
        accel = "tcg"

    cmdline += ["-accel", accel]

    cid: Optional[int] = None
    if QemuDeviceNode.vhost_vsock in qemu_device_fds:
        if config.qemu_vsock_cid == QemuVsockCID.auto:
            cid = find_unused_vsock_cid(config, qemu_device_fds[QemuDeviceNode.vhost_vsock])
        elif config.qemu_vsock_cid == QemuVsockCID.hash:
            cid = hash_to_vsock_cid(hash_output(config))
        else:
            cid = config.qemu_vsock_cid

        if vsock_cid_in_use(qemu_device_fds[QemuDeviceNode.vhost_vsock], cid):
            die(f"VSock connection ID {cid} is already in use by another virtual machine",
                hint="Use QemuVsockConnectionId=auto to have mkosi automatically find a free vsock connection ID")

        cmdline += [
            "-device",
            f"vhost-vsock-pci,guest-cid={cid},vhostfd={qemu_device_fds[QemuDeviceNode.vhost_vsock]}"
        ]

    cmdline += ["-cpu", "max"]

    if config.qemu_gui:
        cmdline += ["-vga", "virtio"]
    else:
        # -nodefaults removes the default CDROM device which avoids an error message during boot
        # -serial mon:stdio adds back the serial device removed by -nodefaults.
        cmdline += [
            "-nographic",
            "-nodefaults",
            "-chardev", "stdio,mux=on,id=console,signal=off",
            "-serial", "chardev:console",
            "-mon", "console",
        ]

    # QEMU has built-in logic to look for the BIOS firmware so we don't need to do anything special for that.
    if firmware.is_uefi():
        assert ovmf
        cmdline += ["-drive", f"if=pflash,format={ovmf.format},readonly=on,file={ovmf.firmware}"]
    notifications: dict[str, str] = {}

    with contextlib.ExitStack() as stack:
        if firmware.is_uefi():
            assert ovmf
            ovmf_vars, ovmf_vars_format = finalize_firmware_variables(config, ovmf, stack)

            cmdline += ["-drive", f"file={ovmf_vars},if=pflash,format={ovmf_vars_format}"]
            if firmware == QemuFirmware.uefi_secure_boot:
                cmdline += [
                    "-global", "ICH9-LPC.disable_s3=1",
                    "-global", "driver=cfi.pflash01,property=secure,value=on",
                ]

        if config.qemu_cdrom and config.output_format in (OutputFormat.disk, OutputFormat.esp):
            # CD-ROM devices have sector size 2048 so we transform disk images into ones with sector size 2048.
            src = (config.output_dir_or_cwd() / config.output_with_compression).resolve()
            fname = src.parent / f"{src.name}-{uuid.uuid4().hex}"
            run(
                [
                    "systemd-repart",
                    "--definitions", "",
                    "--no-pager",
                    "--pretty=no",
                    "--offline=yes",
                    "--empty=create",
                    "--size=auto",
                    "--sector-size=2048",
                    "--copy-from", src,
                    fname,
                ],
                sandbox=config.sandbox(mounts=[Mount(fname.parent, fname.parent), Mount(src, src, ro=True)]),
            )
            stack.callback(lambda: fname.unlink())
        else:
            fname = stack.enter_context(
                copy_ephemeral(config, config.output_dir_or_cwd() / config.output_with_compression)
            )

        apply_runtime_size(config, fname)

        if (
            kernel and
            (
                KernelType.identify(config, kernel) != KernelType.uki or
                not config.architecture.supports_smbios(firmware)
            )
        ):
            kcl = config.kernel_command_line + config.kernel_command_line_extra
        else:
            kcl = config.kernel_command_line_extra

        if kernel:
            cmdline += ["-kernel", kernel]

            if any(s.startswith("root=") for s in kcl):
                pass
            elif config.output_format == OutputFormat.disk:
                # We can't rely on gpt-auto-generator when direct kernel booting so synthesize a root=
                # kernel argument instead.
                root = finalize_root(find_partitions(fname, sandbox=config.sandbox))
                if not root:
                    die("Cannot perform a direct kernel boot without a root or usr partition")

                kcl += [root]
            elif config.output_format == OutputFormat.directory:
                sock = stack.enter_context(start_virtiofsd(config, fname, uidmap=False))
                cmdline += [
                    "-chardev", f"socket,id={sock.name},path={sock}",
                    "-device", f"vhost-user-fs-pci,queue-size=1024,chardev={sock.name},tag=root",
                ]
                kcl += ["root=root", "rootfstype=virtiofs", "rw"]

        for tree in config.runtime_trees:
            sock = stack.enter_context(start_virtiofsd(config, tree.source, uidmap=True))
            tag = tree.target.name if tree.target else tree.source.name
            cmdline += [
                "-chardev", f"socket,id={sock.name},path={sock}",
                "-device", f"vhost-user-fs-pci,queue-size=1024,chardev={sock.name},tag={tag}",
            ]
            target = Path("/root/src") / (tree.target or tree.source.name)
            kcl += [f"systemd.mount-extra={tag}:{target}:virtiofs"]

        if want_scratch(config) or config.output_format in (OutputFormat.disk, OutputFormat.esp):
            cmdline += ["-device", "virtio-scsi-pci,id=scsi"]

        if want_scratch(config):
            scratch = stack.enter_context(generate_scratch_fs(config))
            cmdline += [
                "-drive", f"if=none,id=scratch,file={scratch},format=raw",
                "-device", "scsi-hd,drive=scratch",
            ]
            kcl += [f"systemd.mount-extra=LABEL=scratch:/var/tmp:{config.distribution.filesystem()}"]

        if config.output_format == OutputFormat.cpio:
            cmdline += ["-initrd", fname]
        elif (
            kernel and KernelType.identify(config, kernel) != KernelType.uki and
            "-initrd" not in args.cmdline and
            (config.output_dir_or_cwd() / config.output_split_initrd).exists()
        ):
            cmdline += ["-initrd", config.output_dir_or_cwd() / config.output_split_initrd]

        if config.output_format in (OutputFormat.disk, OutputFormat.esp):
            cmdline += ["-drive", f"if=none,id=mkosi,file={fname},format=raw",
                        "-device", f"scsi-{'cd' if config.qemu_cdrom else 'hd'},drive=mkosi,bootindex=1"]

        if (
            firmware.is_uefi() and
            config.qemu_swtpm != ConfigFeature.disabled and
            find_binary("swtpm", root=config.tools()) is not None
        ):
            sock = stack.enter_context(start_swtpm(config))
            cmdline += ["-chardev", f"socket,id=chrtpm,path={sock}",
                        "-tpmdev", "emulator,id=tpm0,chardev=chrtpm"]

            if config.architecture.is_x86_variant():
                cmdline += ["-device", "tpm-tis,tpmdev=tpm0"]
            elif config.architecture.is_arm_variant():
                cmdline += ["-device", "tpm-tis-device,tpmdev=tpm0"]

        credentials = dict(config.credentials)

        if QemuDeviceNode.vhost_vsock in qemu_device_fds:
            addr, notifications = stack.enter_context(vsock_notify_handler())
            credentials["vmm.notify_socket"] = addr

        for k, v in credentials.items():
            payload = base64.b64encode(v.encode()).decode()
            if config.architecture.supports_smbios(firmware):
                cmdline += ["-smbios", f"type=11,value=io.systemd.credential.binary:{k}={payload}"]
            elif config.architecture.supports_fw_cfg():
                f = stack.enter_context(tempfile.NamedTemporaryFile(prefix="mkosi-fw-cfg", mode="w"))
                f.write(v)
                f.flush()
                cmdline += ["-fw_cfg", f"name=opt/io.systemd.credentials/{k},file={f.name}"]
            elif kernel:
                kcl += [f"systemd.set_credential_binary={k}:{payload}"]

        if (
            kernel and
            (
                KernelType.identify(config, kernel) != KernelType.uki or
                not config.architecture.supports_smbios(firmware)
            )
        ):
            cmdline += ["-append", " ".join(kcl)]
        elif config.architecture.supports_smbios(firmware):
            cmdline += [
                "-smbios",
                f"type=11,value=io.systemd.stub.kernel-cmdline-extra={' '.join(kcl)}",
                "-smbios",
                f"type=11,value=io.systemd.boot.kernel-cmdline-extra={' '.join(kcl)}",
            ]

        for drive in config.qemu_drives:
            file = stack.enter_context(finalize_drive(drive))

            arg = f"if=none,id={drive.id},file={file},format=raw"
            if drive.options:
                arg += f",{drive.options}"

            cmdline += ["-drive", arg]

        cmdline += config.qemu_args
        cmdline += args.cmdline

        if cid is not None:
            stack.enter_context(finalize_state(config, cid))

        with spawn(
            cmdline,
            stdin=sys.stdin,
            stdout=sys.stdout,
            pass_fds=qemu_device_fds.values(),
            env=os.environ | config.environment,
            log=False,
            foreground=True,
            sandbox=config.sandbox(network=True, devices=True, relaxed=True),
        ) as qemu:
            # We have to close these before we wait for qemu otherwise we'll deadlock as qemu will never exit.
            for fd in qemu_device_fds.values():
                os.close(fd)

            allocate_scope(config, qemu.pid)
            register_machine(config, qemu.pid, fname)

    if status := int(notifications.get("EXIT_STATUS", 0)):
        raise subprocess.CalledProcessError(status, cmdline)


def run_ssh(args: Args, config: Config) -> None:
    with flock(INVOKING_USER.runtime_dir() / "machine"):
        if not (p := INVOKING_USER.runtime_dir() / "machine" / f"{config.machine_or_name()}.json").exists():
            die(f"{p} not found, cannot SSH into virtual machine {config.machine_or_name()}",
                hint="Is the machine running and was it built with Ssh=yes and QemuVsock=yes?")

        state = json.loads(p.read_text())

    if not state["SshKey"]:
        die("An SSH key must be configured when booting the image to use 'mkosi ssh'",
            hint="Use 'mkosi genkey' to generate a new SSH key and certificate")

    cmd: list[PathString] = [
        "ssh",
        "-i", state["SshKey"],
        "-F", "none",
        # Silence known hosts file errors/warnings.
        "-o", "UserKnownHostsFile=/dev/null",
        "-o", "StrictHostKeyChecking=no",
        "-o", "LogLevel=ERROR",
        "-o", f"ProxyCommand={state['ProxyCommand']}",
        "root@mkosi",
    ]

    cmd += args.cmdline

    run(
        cmd,
        stdin=sys.stdin,
        stdout=sys.stdout,
        env=os.environ | config.environment,
        log=False,
        sandbox=config.sandbox(network=True, devices=True, relaxed=True),
    )