Emulating ARM machines on QEMU hasn’t been straight-forward due to lack of a standardized way to configure the bootloader across different ARM boards. One had to extract the kernel image, and specify the boot options on the command line (-kernel, -initrd), so QEMU knows what to do with its machine-specific boot code.

We can make things easier with the help of UEFI (namely EDK2, with ARM support), so installing and booting Linux just works like on a x86 PC target.

Prerequisites

• QEMU system emulator for ARM.
• EDK2 binaries for ARM. They can be extracted from the debian package qemu-efi-arm or qemu-efi-aarch64, depending on your target arch.
• Official Debian installer iso for ARM.

Booting the installer

NOTE: This example is for arm32

First of all, create a new disk image via qemu-img. Copy EDK2 FW binaries (AAVMF32_CODE.fd and AAVMF32_VARS.fd, the latter is for hosting volatile variables) and the installer image to the same directory.

We will be emulating the virt board, which has support for virtio devices.

1
2
3
4
5
6
7

qemu-system-arm -M virt -m 512M -cpu cortex-a15 -smp 4 \
-device qemu-xhci -device usb-kbd \
-device usb-storage,drive=install -blockdev file,filename=debian-testing-armhf-DVD-1.iso,node-name=install \
-blockdev qcow2,node-name=root,file.driver=file,file.filename=disk0.qcow2 -device virtio-blk-device,drive=root \
-nic user,model=virtio \
-pflash ./AAVMF32_CODE.fd -pflash ./AAVMF32_VARS.fd \
-device ramfb

• The system is given 512M of RAM and 4 cpus (depending on your QEMU version, this could mean either 4 sockets or 4 cores), the CPU capability is set to cortex-a15.
• -device qemu-xhci -device usb-kbd attaches a low-overhead USB XHCI bus, and a USB keyboard. You could add a mouse if needed. Alternatively, on-board USB support that comes with virt is available by passing -usb.
• Next two lines attach the installer iso as a USB storage device, and the rootfs disk as a virtio block device.
• -nic user,model=virtio enables basic user-mode networking, backed by the virtio NIC.
• -device ramfb adds a simple display device, which is just a frambuffer in guest memory. QEMU ARM system emulator does not emulate a display device by default. The standard std VGA won’t work since the installer environment lacks required DRM kmods.

The graphics & input part can be left-out (with -nographic), in which case the installer will be presented on the serial console.

The guest will now boot into the installer iso. Simply follow the installation instructions, the grub-efi bootloader will be installed to the EFI firmware automatically.

Booting the installed system

No additional configuration is required. Don’t forget to attach the UEFI firmware via -pflash.

1
2
3
4
5
6
7

qemu-system-arm -M virt -m 512M -cpu cortex-a15 -smp 4 \
-device qemu-xhci -device usb-kbd \
-blockdev qcow2,node-name=root,file.driver=file,file.filename=disk0.qcow2 -device virtio-blk-device,drive=root \
-nic user,model=virtio,hostfwd=tcp::2345-:22 \
-pflash ./AAVMF32_CODE.fd -pflash ./AAVMF32_VARS.fd \
-device VGA
-virtfs local,path=/host/path/to/shared/,id=share,mount_tag=share,security_model=mapped

There are a few additional configurations:

• Host porting forwarding is enabled for host port 2345, to guest port 22. This way we are able to ssh directly into the guest system.
• Attach a shared folder to the guest, backed by 9pfs. The folder can be mounted in the guest via mount -t 9p -o trans=virtio share /path/to/mount

Voilà! Your new virtual ARM system is ready to go!