VFIO

Virtual Function I/O

Set of technologies that allows to 'push' device(s) to virtual machine.
The device is managed by the VM only, 'typical' use case for Linux hosts: Windows guest VM with GPU access.

Allows writing userspace drivers.

GPU passthrough Debian setup

Ensure:

> egrep -q '^flags.*(svm|vmx)' /proc/cpuinfo && echo virtualization extensions available
virtualization extensions available
> aptitude install qemu-kvm
...

Enable IOMMU (mapping of device address to main memory):

> cat /etc/default/grub.d/vfio.cfg
GRUB_CMDLINE_LINUX_DEFAULT="quiet intel_iommu=on iommu=pt"

Find PCI port, using script that groups devices by their IOMMU groups

#!/bin/bash
shopt -s nullglob
for g in /sys/kernel/iommu_groups/*; do
    echo "IOMMU Group ${g##*/}:"
    for d in $g/devices/*; do
        echo -e "\t$(lspci -nns ${d##*/})"
    done;
done;

It may not be possible to 'push' single device to VM, normally whole IOMMU group is 'pushed'. This means that all devices belonging to such group won't be available on host.

> cat /usr/share/initramfs-tools/modules.d/vfio
vfio_pci ids=10df:1122,10de:1133,10de:1aaa,11de:bbbb
vfio_iommu_type1
> update-initramfs -u -k all

Disable any drivers that may take over device before VFIO (kernel)

> cat /etc/modprobe.d/nvidia.conf
softdep nouveau pre: vfio-pci 
softdep nvidia pre: vfio-pci 
softdep nvidia* pre: vfio-pci

> cat /etc/modprobe.d/blacklist-nvidia-nouveau.conf
blacklist nouveau
options nouveau modeset=0

Reboot, and verify

> lspci -v
01:00.0 VGA compatible controller: NVIDIA ... [GeForce ... Rev. A] (rev ...) (prog-if 00 [VGA controller])
...
        Kernel driver in use: vfio-pci
...

Create VM, attach GPU, configure evdev so that same mouse is shared between host and guest.

References

1. https://www.kernel.org/doc/Documentation/vfio.txt
2. https://passthroughpo.st/gpu-debian/
3. https://passthroughpo.st/using-evdev-passthrough-seamless-vm-input/
4. https://mathiashueber.com/windows-virtual-machine-gpu-passthrough-ubuntu/
5. https://wiki.debian.org/VGAPassthrough