OpenBSD under QEMU

These notes generalise the working cases from obsd.sh, a sysupgrade(8) influenced helper for headless OpenBSD VMs with serial console output. With current QEMU on an amd64 host, emulated systems are fast enough for ports work; riscv64 builds gcc-16.1.0 in 1 to 2 days, close to a real sparc64 machine.

alpha

OpenBSD/alpha is blocked by incomplete SRM emulation. The port expects bootinfo, PTBR, PROM state, and SRM disk callbacks; QEMU’s clipper PALcode is not a complete SRM console.

amd64

OpenBSD/amd64 works with standard qemu-system-x86_64 emulation and virtio networking:

qemu-system-x86_64 \
	-nographic \
	-m 32G \
	-smp 8 \
	-hda amd64.qcow2 \
	-netdev user,id=net0 \
	-device virtio-net-pci,netdev=net0

qemu-system-x86_64 \
	-nographic \
	-m 32G \
	-smp 8 \
	-hda amd64.qcow2 \
	-netdev user,id=net0 \
	-device virtio-net-pci,netdev=net0

Serial console selection remains manual:

stty com0 115200
set tty com0

arm64

OpenBSD/arm64 works on the QEMU virt machine with U-Boot from the OpenBSD u-boot-aarch64 port:

qemu-system-aarch64 \
	-machine virt \
	-cpu cortex-a57 \
	-nographic \
	-bios /usr/local/share/u-boot/qemu_arm64/u-boot.bin \
	-m 32G \
	-smp 8 \
	-drive file=arm64.qcow2,format=qcow2,if=none,id=hd0 \
	-device virtio-blk-pci,drive=hd0,bootindex=1 \
	-netdev user,id=net0 \
	-device virtio-net-device,netdev=net0

qemu-system-aarch64 \
	-machine virt \
	-cpu cortex-a57 \
	-nographic \
	-bios /usr/local/share/u-boot/qemu_arm64/u-boot.bin \
	-m 32G \
	-smp 8 \
	-drive file=arm64.qcow2,format=qcow2,if=none,id=hd0 \
	-device virtio-blk-pci,drive=hd0,bootindex=1 \
	-netdev user,id=net0 \
	-device virtio-net-device,netdev=net0

armv7

OpenBSD/armv7 works on the QEMU virt machine with cortex-a15, U-Boot from the OpenBSD u-boot-arm port, 3G of RAM, and a uniprocessor guest:

qemu-system-arm \
	-machine virt,virtualization=on \
	-cpu cortex-a15 \
	-nographic \
	-bios /usr/local/share/u-boot/qemu_arm/u-boot.bin \
	-m 3G \
	-smp 1 \
	-drive file=armv7.qcow2,format=qcow2,if=none,id=hd0 \
	-device virtio-blk-device,drive=hd0,bootindex=1 \
	-netdev user,id=net0 \
	-device virtio-net-device,netdev=net0

qemu-system-arm \
	-machine virt,virtualization=on \
	-cpu cortex-a15 \
	-nographic \
	-bios /usr/local/share/u-boot/qemu_arm/u-boot.bin \
	-m 3G \
	-smp 1 \
	-drive file=armv7.qcow2,format=qcow2,if=none,id=hd0 \
	-device virtio-blk-device,drive=hd0,bootindex=1 \
	-netdev user,id=net0 \
	-device virtio-net-device,netdev=net0

At 4G of RAM, devices hang; OpenBSD/armv7 does not support SMP.

Virtio networking needs an OpenBSD if_vio.c alignment fix¹. USB networking avoids that path, but the installer and installed system use different interface names, cdce0 and urndis0; other NICs, including em0 and e1000, also hung.

The target disk has an MSDOS boot partition visible as i:, so autopartitioning must fit within 14 OpenBSD partitions.

hppa

OpenBSD/hppa exposes several partial boot paths, but no usable installer. C3700 and A400 load bsd.rd, then stop around SPID setup. B160L prints the OpenBSD copyright, then hangs before cpu_startup(). lif79.img reaches BOOT and can open dk0a:/bsd, but ramdisk loading fails with a bogus heap allocation size.

i386

OpenBSD/i386 follows the same path as OpenBSD/amd64: headless boot, virtio networking, and manual serial console selection².

qemu-system-i386 \
	-nographic \
	-m 32G \
	-smp 8 \
	-hda i386.qcow2 \
	-netdev user,id=net0 \
	-device virtio-net-pci,netdev=net0

qemu-system-i386 \
	-nographic \
	-m 32G \
	-smp 8 \
	-hda i386.qcow2 \
	-netdev user,id=net0 \
	-device virtio-net-pci,netdev=net0

landisk

OpenBSD/landisk has no matching QEMU machine. The port expects IO-DATA LANDISK; QEMU provides only r2d-plus.

loongson

OpenBSD/loongson has no tested QEMU path to a serial installer. Fuloong 2E does not produce usable serial installer output. loongson3-virt reaches UEFI with non-free bios_loongson3.bin from Loongson Community’s firmware repository, but OpenBSD media contain bsd.rd without an EFI loader, so firmware boot stops at the UEFI shell.

luna88k

OpenBSD/luna88k has no matching QEMU m88k system emulator.

macppc

OpenBSD/macppc reaches the ramdisk under qemu-system-ppc, but not a usable installer. The guest hangs after printing the bad clock warning.

octeon

OpenBSD/octeon has no usable QEMU system target. QEMU includes an Octeon CPU model, but not the corresponding machine, firmware, and device set.

powerpc64

OpenBSD/powerpc64 requires a firmware handoff; direct -kernel bsd.rd does not provide it. PowerNV with manually extracted pnor.BOOTKERNEL images from talos-ii-v2.10.pnor gets farther than direct kernel loading and reaches OpenBSD’s early Hello, World!, then hangs while QEMU consumes CPU. pseries is not a supported OpenBSD/powerpc64 platform.

riscv64

OpenBSD/riscv64 works with OpenSBI and U-Boot from the OpenBSD u-boot-riscv64 port:

qemu-system-riscv64 \
	-machine virt \
	-nographic \
	-bios /usr/local/share/opensbi/generic/fw_jump.bin \
	-kernel /usr/local/share/u-boot/qemu-riscv64_smode/u-boot.bin \
	-m 32G \
	-smp 8 \
	-hda riscv64.qcow2 \
	-netdev user,id=net0 \
	-device virtio-net-device,netdev=net0

qemu-system-riscv64 \
	-machine virt \
	-nographic \
	-bios /usr/local/share/opensbi/generic/fw_jump.bin \
	-kernel /usr/local/share/u-boot/qemu-riscv64_smode/u-boot.bin \
	-m 32G \
	-smp 8 \
	-hda riscv64.qcow2 \
	-netdev user,id=net0 \
	-device virtio-net-device,netdev=net0

sparc64

OpenBSD/sparc64 works on the QEMU sun4u machine:

qemu-system-sparc64 \
	-machine sun4u \
	-nographic \
	-m 4G \
	-smp 1 \
	-hda sparc64.qcow2 \
	-net nic,model=sunhme \
	-net user

qemu-system-sparc64 \
	-machine sun4u \
	-nographic \
	-m 4G \
	-smp 1 \
	-hda sparc64.qcow2 \
	-net nic,model=sunhme \
	-net user

QEMU supports only one CPU for the sun4u machine; higher memory also hits OpenBIOS allocation failures:

out of malloc memory (28)!
Unhandled Exception 0x0000000000000030

TFTP through OpenBIOS did not work either:

Trying net...
No valid state has been set by load or init-program