Virtio-Venus 3D Acceleration

Part of CachyOS Wiki Notes. From the official CachyOS wiki (last updated 2025-11-24).

Virtio-Venus (near-native 3D acceleration)

URL note: /virtualization/virtio_venus/ (underscore) 404s — the live page is the hyphenated slug /virtualization/virtio-venus/.

For guests that use libvulkan — Linux, BSDs, Android — you can get near-native performance by translating calls from the VM to Vulkan, then directly to the GPU and back, without passing the GPU through to the VM.

Limitation: Virtio-Venus is not exposed in VMM, so it requires qemu-cli. You need to know the VM’s name and where it lives.

Example invocation

qemu-system-x86_64                                                                             \
    -enable-kvm                                                                                \
    -M q35                                                                                     \
    -smp 6                                                                                     \
    -m 12G                                                                                     \
    -cpu host                                                                                  \
    -net nic,model=virtio                                                                      \
    -net user,hostfwd=tcp::2222-:22                                                            \
    -device virtio-sound-pci,audiodev=my_audiodev -audiodev pipewire,id=my_audiodev            \
    -device virtio-vga-gl,hostmem=4G,blob=true,venus=true                                      \
    -vga none                                                                                  \
    -display gtk,gl=on,show-cursor=on                                                          \
    -usb -device usb-tablet                                                                    \
    -object memory-backend-memfd,id=mem1,size=12G                                              \
    -machine memory-backend=mem1                                                               \
    -drive if=pflash,format=raw,readonly=on,file=/usr/share/edk2/x64/OVMF_CODE.secboot.4m.fd   \
    -drive if=pflash,format=raw,file=.config/libvirt/qemu/nvram/archlinux_VARS.fd              \
    -drive file=.local/share/libvirt/images/archlinux.qcow2

Flags explained

• -smp 6 — 6 CPU cores.

• -m 12G — 12 GB RAM.

• -net user,hostfwd=tcp::2222-:22 — forwards guest port 22 to host port 2222:

  ssh -p 2222 vmusername@vmipaddress

• -device virtio-vga-gl,hostmem=4G,blob=true,venus=true — the Venus driver, not yet in virt-manager; once it is, everything here except user mode is superseded. hostmem=4G lets the VM use up to 4 GB of your VRAM.

• -object memory-backend-memfd,id=mem1,size=12G — size must match the RAM you gave the VM.

• -drive if=pflash,...OVMF_CODE.secboot.4m.fd — the firmware file path.

• -drive if=pflash,format=raw,file=.config/libvirt/qemu/nvram/archlinux_VARS.fd — the VM’s nvram; without it (or if read-only) the VM won’t run.

• -drive file=.local/share/libvirt/images/archlinux.qcow2 — the VM’s storage.

• Audio uses pipewire instead of ich9 in the example; the page says that detail is irrelevant.