diff --git a/osbase/test/qemu/launch.go b/osbase/test/qemu/launch.go
new file mode 100644
index 0000000..52a1492
--- /dev/null
+++ b/osbase/test/qemu/launch.go
@@ -0,0 +1,316 @@
+// Copyright The Monogon Project Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+// Package qemu implements test harnesses for running qemu VMs from tests.
+package qemu
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"os"
+	"os/exec"
+	"strconv"
+	"strings"
+	"syscall"
+
+	"golang.org/x/sys/unix"
+
+	"source.monogon.dev/osbase/freeport"
+)
+
+type QemuValue map[string][]string
+
+// ToOption encodes structured data into a QEMU option. Example: "test", {"key1":
+// {"val1"}, "key2": {"val2", "val3"}} returns "test,key1=val1,key2=val2,key2=val3"
+func (value QemuValue) ToOption(name string) string {
+	var optionValues []string
+	if name != "" {
+		optionValues = append(optionValues, name)
+	}
+	for name, values := range value {
+		if len(values) == 0 {
+			optionValues = append(optionValues, name)
+		}
+		for _, val := range values {
+			optionValues = append(optionValues, fmt.Sprintf("%v=%v", name, val))
+		}
+	}
+	return strings.Join(optionValues, ",")
+}
+
+// PrettyPrintQemuArgs prints the given QEMU arguments to stderr.
+func PrettyPrintQemuArgs(name string, args []string) {
+	var argsFmt string
+	for _, arg := range args {
+		argsFmt += arg
+		if !strings.HasPrefix(arg, "-") {
+			argsFmt += "\n  "
+		} else {
+			argsFmt += " "
+		}
+	}
+	fmt.Fprintf(os.Stderr, "Running %s:\n  %s\n", name, argsFmt)
+}
+
+// PortMap represents where VM ports are mapped to on the host. It maps from the VM
+// port number to the host port number.
+type PortMap map[uint16]uint16
+
+// ToQemuForwards generates QEMU hostfwd values (https://qemu.weilnetz.de/doc/qemu-
+// doc.html#:~:text=hostfwd=) for all mapped ports.
+func (p PortMap) ToQemuForwards() []string {
+	var hostfwdOptions []string
+	for vmPort, hostPort := range p {
+		hostfwdOptions = append(hostfwdOptions, fmt.Sprintf("tcp::%d-:%d", hostPort, vmPort))
+	}
+	return hostfwdOptions
+}
+
+// IdentityPortMap returns a port map where each given port is mapped onto itself
+// on the host. This is mainly useful for development against Metropolis. The dbg
+// command requires this mapping.
+func IdentityPortMap(ports []uint16) PortMap {
+	portMap := make(PortMap)
+	for _, port := range ports {
+		portMap[port] = port
+	}
+	return portMap
+}
+
+// ConflictFreePortMap returns a port map where each given port is mapped onto a
+// random free port on the host. This is intended for automated testing where
+// multiple instances of Metropolis nodes might be running. Please call this
+// function for each Launch command separately and as close to it as possible since
+// it cannot guarantee that the ports will remain free.
+func ConflictFreePortMap(ports []uint16) (PortMap, error) {
+	portMap := make(PortMap)
+	for _, port := range ports {
+		mappedPort, listenCloser, err := freeport.AllocateTCPPort()
+		if err != nil {
+			return portMap, fmt.Errorf("failed to get free host port: %w", err)
+		}
+		// Defer closing of the listening port until the function is done and all ports are
+		// allocated
+		defer listenCloser.Close()
+		portMap[port] = mappedPort
+	}
+	return portMap, nil
+}
+
+// GuestServiceMap maps an IP/port combination inside the virtual guest network
+// to a TCPAddr reachable by the host. If the guest connects to the virtual
+// address/port, this connection gets forwarded to the host.
+type GuestServiceMap map[*net.TCPAddr]net.TCPAddr
+
+// ToQemuForwards generates QEMU guestfwd values (https://qemu.weilnetz.de/doc/qemu-
+// doc.html#:~:text=guestfwd=) for all mapped addresses.
+func (p GuestServiceMap) ToQemuForwards() []string {
+	var guestfwdOptions []string
+	for guestAddr, hostAddr := range p {
+		guestfwdOptions = append(guestfwdOptions, fmt.Sprintf("tcp:%s-tcp:%s", guestAddr.String(), hostAddr.String()))
+	}
+	return guestfwdOptions
+}
+
+// NewSocketPair creates a new socket pair. By connecting both ends to different
+// instances you can connect them with a virtual "network cable". The ends can be
+// passed into the ConnectToSocket option.
+func NewSocketPair() (*os.File, *os.File, error) {
+	fds, err := unix.Socketpair(unix.AF_UNIX, syscall.SOCK_STREAM, 0)
+	if err != nil {
+		return nil, nil, fmt.Errorf("failed to call socketpair: %w", err)
+	}
+
+	fd1 := os.NewFile(uintptr(fds[0]), "network0")
+	fd2 := os.NewFile(uintptr(fds[1]), "network1")
+	return fd1, fd2, nil
+}
+
+// HostInterfaceMAC is the MAC address the host SLIRP network interface has if it
+// is not disabled (see DisableHostNetworkInterface in MicroVMOptions)
+var HostInterfaceMAC = net.HardwareAddr{0x02, 0x72, 0x82, 0xbf, 0xc3, 0x56}
+
+// MicroVMOptions contains all options to start a MicroVM
+type MicroVMOptions struct {
+	// Name is a human-readable identifier to be used in debug output.
+	Name string
+
+	// Path to the ELF kernel binary
+	KernelPath string
+
+	// Path to the Initramfs
+	InitramfsPath string
+
+	// Cmdline contains additional kernel commandline options
+	Cmdline string
+
+	// SerialPort is a File(descriptor) over which you can communicate with the serial
+	// port of the machine It can be set to an existing file descriptor (like
+	// os.Stdout/os.Stderr) or you can use NewSocketPair() to get one end to talk to
+	// from Go.
+	SerialPort io.Writer
+
+	// ExtraChardevs can be used similar to SerialPort, but can contain an arbitrary
+	// number of additional serial ports
+	ExtraChardevs []*os.File
+
+	// ExtraNetworkInterfaces can contain an arbitrary number of file descriptors which
+	// are mapped into the VM as virtio network interfaces. The first interface is
+	// always a SLIRP-backed interface for communicating with the host.
+	ExtraNetworkInterfaces []*os.File
+
+	// PortMap contains ports that are mapped to the host through the built-in SLIRP
+	// network interface.
+	PortMap PortMap
+
+	// GuestServiceMap contains TCP services made available in the guest virtual
+	// network which are running on the host.
+	GuestServiceMap GuestServiceMap
+
+	// DisableHostNetworkInterface disables the SLIRP-backed host network interface
+	// that is normally the first network interface. If this is set PortMap is ignored.
+	// Mostly useful for speeding up QEMU's startup time for tests.
+	DisableHostNetworkInterface bool
+
+	// PcapDump can be used to dump all network traffic to a pcap file.
+	// If unset, no dump is created.
+	PcapDump string
+}
+
+// RunMicroVM launches a tiny VM mostly intended for testing. Very quick to boot
+// (<40ms).
+func RunMicroVM(ctx context.Context, opts *MicroVMOptions) error {
+	// Generate options for all the file descriptors we'll be passing as virtio "serial
+	// ports"
+	var extraArgs []string
+	for idx := range opts.ExtraChardevs {
+		idxStr := strconv.Itoa(idx)
+		id := "extra" + idxStr
+		// That this works is pretty much a hack, but upstream QEMU doesn't have a
+		// bidirectional chardev backend not based around files/sockets on the disk which
+		// are a giant pain to work with. We're using QEMU's fdset functionality to make
+		// FDs available as pseudo-files and then "ab"using the pipe backend's fallback
+		// functionality to get a single bidirectional chardev backend backed by a passed-
+		// down RDWR fd. Ref https://lists.gnu.org/archive/html/qemu-devel/2015-
+		// 12/msg01256.html
+		addFdConf := QemuValue{
+			"set": {idxStr},
+			"fd":  {strconv.Itoa(idx + 3)},
+		}
+		chardevConf := QemuValue{
+			"id":   {id},
+			"path": {"/dev/fdset/" + idxStr},
+		}
+		deviceConf := QemuValue{
+			"chardev": {id},
+		}
+		extraArgs = append(extraArgs, "-add-fd", addFdConf.ToOption(""),
+			"-chardev", chardevConf.ToOption("pipe"), "-device", deviceConf.ToOption("virtserialport"))
+	}
+
+	for idx := range opts.ExtraNetworkInterfaces {
+		id := fmt.Sprintf("net%v", idx)
+		netdevConf := QemuValue{
+			"id": {id},
+			"fd": {strconv.Itoa(idx + 3 + len(opts.ExtraChardevs))},
+		}
+		extraArgs = append(extraArgs, "-netdev", netdevConf.ToOption("socket"), "-device", "virtio-net-device,netdev="+id)
+	}
+
+	// This sets up a minimum viable environment for our Linux kernel. It clears all
+	// standard QEMU configuration and sets up a MicroVM machine
+	// (https://github.com/qemu/qemu/blob/master/docs/microvm.rst) with all legacy
+	// emulation turned off. This means the only "hardware" the Linux kernel inside can
+	// communicate with is a single virtio-mmio region. Over that MMIO interface we run
+	// a paravirtualized RNG (since the kernel in there has nothing to gather that from
+	// and it delays booting), a single paravirtualized console and an arbitrary number
+	// of extra serial ports for talking to various things that might run inside. The
+	// kernel, initramfs and command line are mapped into VM memory at boot time and
+	// not loaded from any sort of disk. Booting and shutting off one of these VMs
+	// takes <100ms.
+	baseArgs := []string{
+		"-nodefaults", "-no-user-config", "-nographic", "-no-reboot",
+		"-accel", "kvm", "-cpu", "host",
+		"-m", "1G",
+		// Needed because QEMU does not boot without specifying the qboot bios
+		// even tho the documentation clearly states that this is the default.
+		"-bios", "/usr/share/qemu/qboot.rom",
+		"-M", "microvm,x-option-roms=off,pic=off,pit=off,rtc=off,isa-serial=off",
+		"-kernel", opts.KernelPath,
+		// We force using a triple-fault reboot strategy since otherwise the kernel first
+		// tries others (like ACPI) which are not available in this very restricted
+		// environment. Similarly we need to override the boot console since there's
+		// nothing on the ISA bus that the kernel could talk to. We also force quiet for
+		// performance reasons.
+		"-append", "reboot=t console=hvc0 quiet " + opts.Cmdline,
+		"-initrd", opts.InitramfsPath,
+		"-device", "virtio-rng-device,max-bytes=1024,period=1000",
+		"-device", "virtio-serial-device,max_ports=16",
+		"-chardev", "stdio,id=con0", "-device", "virtconsole,chardev=con0",
+	}
+
+	if !opts.DisableHostNetworkInterface {
+		qemuNetType := "user"
+		qemuNetConfig := QemuValue{
+			"id":        {"usernet0"},
+			"net":       {"10.42.0.0/24"},
+			"dhcpstart": {"10.42.0.10"},
+		}
+		if opts.PortMap != nil {
+			qemuNetConfig["hostfwd"] = opts.PortMap.ToQemuForwards()
+		}
+		if opts.GuestServiceMap != nil {
+			qemuNetConfig["guestfwd"] = opts.GuestServiceMap.ToQemuForwards()
+		}
+
+		baseArgs = append(baseArgs, "-netdev", qemuNetConfig.ToOption(qemuNetType),
+			"-device", "virtio-net-device,netdev=usernet0,mac="+HostInterfaceMAC.String())
+	}
+
+	if !opts.DisableHostNetworkInterface && opts.PcapDump != "" {
+		qemuNetDump := QemuValue{
+			"id":     {"usernet0"},
+			"netdev": {"usernet0"},
+			"file":   {opts.PcapDump},
+		}
+		extraArgs = append(extraArgs, "-object", qemuNetDump.ToOption("filter-dump"))
+	}
+
+	var stdErrBuf bytes.Buffer
+	cmd := exec.CommandContext(ctx, "/usr/bin/qemu-system-x86_64", append(baseArgs, extraArgs...)...)
+	cmd.Stdout = opts.SerialPort
+	cmd.Stderr = &stdErrBuf
+
+	cmd.ExtraFiles = append(cmd.ExtraFiles, opts.ExtraChardevs...)
+	cmd.ExtraFiles = append(cmd.ExtraFiles, opts.ExtraNetworkInterfaces...)
+
+	PrettyPrintQemuArgs(opts.Name, cmd.Args)
+
+	err := cmd.Run()
+	// If it's a context error, just quit. There's no way to tell a
+	// killed-due-to-context vs killed-due-to-external-reason error returned by Run,
+	// so we approximate by looking at the context's status.
+	if err != nil && ctx.Err() != nil {
+		return ctx.Err()
+	}
+
+	var exerr *exec.ExitError
+	if err != nil && errors.As(err, &exerr) {
+		exerr.Stderr = stdErrBuf.Bytes()
+		newErr := QEMUError(*exerr)
+		return &newErr
+	}
+	return err
+}
+
+// QEMUError is a special type of ExitError used when QEMU fails. In addition to
+// normal ExitError features it prints stderr for debugging.
+type QEMUError exec.ExitError
+
+func (e *QEMUError) Error() string {
+	return fmt.Sprintf("%v: %v", e.String(), string(e.Stderr))
+}