Complete-Single-GPU-Passthrough/QEMU.md

PLAIN QEMU WITHOUT LIBVIRT

WORK IN PROGRESS

ONLY USE THIS IF YOU KNOW WHAT YOU'RE DOING

I don't use VMs so I didn't test it extensively.
Only tested it for if it actually passes GPU, and it seems to do the job.
You need to figure out missing pieces on your own.

Passthrough can be done with plain qemu without using libvirt.
The general idea of using plain qemu is to avoid managing libvirt configurations and rather use a single portable script.

Stuffs taken from YuriAlek's script.

Create disk image with QEMU.

qemu-img create -f raw Disk.img 256G

The script should be run as superuser.
Run with nohup to make the script run even after terminal closes.

doas nohup ./passthrough.sh > ~/qemu.log 2>&1

Use lspci -nn command to get device ids.

01:00.0 VGA compatible controller [0300]: NVIDIA Corporation GP106 [GeForce GTX 1060 6GB] [10de:1c03] (rev a1)
01:00.1 Audio device [0403]: NVIDIA Corporation GP106 High Definition Audio Controller [10de:10f1] (rev a1)

#!/bin/sh

ULIMIT=$(ulimit -a | grep "max locked memory" | awk '{print $6}')

# Replace 4 with the amount of RAM you supply to the VM (in GB)
ULIMIT_TARGET=$((4 * 1048576 + 100000))

# 

VIDEOID="10de 1c03"
VIDEOBUSID="0000:01:00.0"
AUDIOID="10de 10f1"
AUDIOBUSID="0000:01:00.1"

ulimit -l $ULIMIT_TARGET

# Should be run before VM starts
function init_vm() {
	# Stop display manager (if any exists)
	# rc-service xdm stop
	# systemctl stop display-manager 
	pkill -9 emacs 

	sleep 1
	# Unbind EFI-framebuffer
	echo efi-framebuffer.0 > /sys/bus/platform/drivers/efi-framebuffer/unbind
	
	# Unload GPU modules
	modprobe -r nvidia_drm nvidia_modeset nvidia_uvm nvidia snd_hda_intel
	# modprobe -r amdgpu 
	
	# Load vfio modules
	modprobe vfio-pci

	# Bind drivers to vfio
	echo $VIDEOID > /sys/bus/pci/drivers/vfio-pci/new_id
	echo $VIDEOBUSID > /sys/bus/pci/devices/0000:01:00.0/driver/unbind
	echo $VIDEOBUSID > /sys/bus/pci/drivers/vfio-pci/bind
	echo $VIDEOID > /sys/bus/pci/drivers/vfio-pci/remove_id

	echo $AUDIOID > /sys/bus/pci/drivers/vfio-pci/new_id
	echo $AUDIOBUSID > /sys/bus/pci/devices/0000:01:00.1/driver/unbind
	echo $AUDIOBUSID > /sys/bus/pci/drivers/vfio-pci/bind
	echo $AUDIOID > /sys/bus/pci/drivers/vfio-pci/remove_id
}

# Start VM
function start_vm() {
	qemu-system-x86_64 \
		-runas qaidvoid \
		-nodefaults \
		-enable-kvm \
		-machine kernel_irqchip=on \
		-cpu host,kvm=off,hv_vendor_id=nil \
		-m 4G \
		-name "Guix" \
		-smp cores=2 \
		-drive file=/home/qaidvoid/VM/Disk.img,if=virtio,format=raw \
		-drive file=/home/qaidvoid/Downloads/guix-system-install-1.2.0.x86_64-linux.iso,media=cdrom \
		-serial none \
		-net nic \
		-net user \
		-vga none \
		-nographic \
		-device vfio-pci,host=01:00.0,x-vga=on,multifunction=on \
		-device vfio-pci,host=01:00.1 \
		-object input-linux,id=mouse1,evdev=/dev/input/by-id/usb-PixArt_HP_USB_Optical_Mouse-event-mouse \
		-object input-linux,id=kbd1,evdev=/dev/input/by-id/usb-Chicony_USB_Keyboard-event-kbd,grab_all=on,repeat=on \
		-device virtio-keyboard \
		-device virtio-mouse
}

# Should be run on VM shutdown
function stop_vm() {
	# Unload VFIO modules
	modprobe -r vfio-pci
	ulimit -l $ULIMIT

	# Load GPU modules
	modprobe nvidia_drm
	modprobe nvidia_modeset
	modprobe nvidia_uvm
	modprobe nvidia
	# modprobe amdgpu
	
	# Bind EFI framebuffer to host
	echo "efi-framebuffer.0" > /sys/bus/platform/drivers/efi-framebuffer/bind
	
	# Restart Display Manager - I don't have display manager to test
	# rc-service xdm start
	# systemctl start display-manager

	# Couldn't get display back on host..
	# Rebooting seems to be the best option
	reboot
}

init_vm
start_vm
stop_vm