Requirements

Mirrored from the FEMU repository

This page is hw/femu/docs/getting-started/requirements.md at FEMU 39a55eeb6 (2026-10-02), licensed GPL-2.0-or-later. Send corrections to the FEMU repository.

What the host and the guest need before you build and run FEMU. The quick start assumes everything on this page.

Host

Operating system and CPU

FEMU runs on an x86_64 Linux host with hardware virtualization (Intel VT-x or AMD-V). Run it on a physical machine. Nested virtualization works but distorts the emulated latency, and WSL is not supported.

FEMU is based on QEMU 10.1, which needs Python 3.9 or newer and GLib 2.66 or newer. Check yours:

python3 --version
pkg-config --modversion glib-2.0

Distribution	Python	GLib	Status
Ubuntu 24.04 LTS	3.12	2.80	Built in CI
Ubuntu 22.04 LTS	3.10	2.72	Built in CI
Ubuntu 20.04 and older	3.8	2.64	Cannot build with stock packages

Other distributions with new enough Python and GLib should build FEMU, but CI does not test them. pkgdep.sh installs dependencies on Debian and Ubuntu only; on other distributions install the equivalents of the packages listed in build.md.

CI builds FEMU with femu-compile.sh on Ubuntu 22.04 and 24.04 (.github/workflows/ci.yml). It runs the unit tests and qtests and starts every mode without a guest. It does not boot a guest. The guest-level quick start was last run end to end on a Pop!_OS 24.04 host (Ubuntu 24.04 base) with Linux 6.18.

KVM access

The run scripts start QEMU with -enable-kvm. Check that KVM is loaded and that you can open it:

ls -l /dev/kvm
id -nG | grep -w kvm

If /dev/kvm is missing, enable virtualization in the BIOS and load the module (sudo modprobe kvm_intel or sudo modprobe kvm_amd). If you are not in the kvm group, add yourself and log in again:

sudo usermod -aG kvm "$USER"

The run-*.sh launchers run QEMU with sudo, so they work without the group. make-guest-image.sh runs without root and needs the group.

Memory

The emulated SSD lives in host DRAM. Nothing is stored in a file, and nothing written to it survives a shutdown. Plan host memory as:

host RAM needed = devsz_mb (the emulated SSD) + guest RAM (-m) + about 1 GiB for QEMU

Launcher	devsz_mb	Guest -m	Free host RAM needed
run-blackbox.sh (BBSSD)	12288	4G	about 17 GiB
run-nossd.sh, run-zns.sh, run-whitebox.sh, run-csd.sh	4096	4G	about 9 GiB

To fit a smaller host, lower ssd_size in run-blackbox.sh and the geometry with it (see the property reference).

FEMU locks the device memory (mlock) so page faults do not distort latency. Under sudo the limit does not apply. If you run QEMU as a normal user, raise the limit with ulimit -l unlimited (or /etc/security/limits.conf). Without it the device still starts and prints a warning, and latency is less precise.

Hugepages

The standard run-*.sh launchers do not need hugepages. femu-cxl-ssd with der=cylon needs a shared, preallocated hugetlb memory backend and a modified host kernel (see cxlssd.md).

Disk

The source tree and one build take about 3 GiB. The guest image built by make-guest-image.sh uses about 2.5 GiB on disk (32 GiB virtual), plus a 0.6 GiB download cache.

CPU cores

The launchers give the guest 4 vCPUs (-smp 4). FEMU adds its own polling threads. 8 host cores is a comfortable minimum.

Guest

Kernel per mode

Mode	femu_mode	Guest kernel	Notes
NoSSD	2 (default)	any with NVMe
BlackBox SSD (BBSSD)	1	any with NVMe
OpenChannel SSD 1.2 / 2.0	0	4.16 to 5.14 (2.0 needs 4.17 or newer)	LightNVM was removed in Linux 5.15. On newer kernels use SPDK.
Zoned Namespace (ZNS)	3	5.9 or newer, CONFIG_BLK_DEV_ZONED=y
Key-value (KV)	5	6.0 or newer	No block device. The namespace appears as the generic character device /dev/ngXnY. Linux 5.9 to 5.19 do not attach the namespace at all.
Computational storage (CSD)	4	any with NVMe	Guest tools in hw/femu/tests/csd/.
Flexible Data Placement (FDP)	1, with femu-subsys,fdp=on	any with NVMe	Use passthrough commands or io_uring to send placement hints.
CXL SSD (femu-cxl-ssd)	not a femu_mode	CXL region support: CONFIG_CXL_BUS, CXL_PCI, CXL_ACPI, CXL_MEM, CXL_PORT, CXL_REGION, DEV_DAX, DEV_DAX_KMEM	Needs cxl-cli and daxctl in the guest.

The image from make-guest-image.sh runs Ubuntu 24.04 with Linux 6.8. It covers every mode except OCSSD.

Guest tools

• nvme-cli and fio for every NVMe mode. make-guest-image.sh installs both.
• ZNS needs nvme-cli 1.12 or newer for nvme zns.
• nvme-cli 2.8, the version in Ubuntu 24.04, double-frees and crashes after every successful Persistent Event Log read (nvme persistent-event-log). Build nvme-cli 3.x from source in the guest if you need that log. Other commands work.
• CXL: cxl-cli, daxctl and ndctl (make-guest-image.sh --cxl).