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GPU Pass-through Manjaro Walk-through

Today I would like to quickly talk about how to setup a GPU pass-through for a decidated GPU on a qemu/kvm windows 10 guest. For this to work you need two video cards.

First we need to enable IOMMU via AMD-Vi or Intel Vt-d in the BIOS. Now lets quickly open and edit the /etc/default/grub and append the following to the GRUB_CMDLINE_LINUX_DEFAULT line:

GRUB_CMDLINE_LINUX_DEFAULT=" ... intel_iommu=on iommu=pt pcie_acs_override=downstream hugepages=2048"

You do not remove other kernel commands such as quiet and resume=UUID if you have them. Another important note, you only need pcie_acs_override=downstream if you are using an ACS override patch.

After modifying the grub file you need to update grub with update-grub and reboot.

Using lspci -nn we can find the device IDs of the GPU that we want to use. In my case, i want to use my GTX 750ti as the GPU to pass-through.

02:00.0 VGA compatible controller [0300]: NVIDIA Corporation GM107 [GeForce GTX 750 Ti] [10de:1380] (rev a2)
02:00.1 Audio device [0403]: NVIDIA Corporation Device [10de:0fbc] (rev a1)

Here i will copy 10de:1380 and 10de:0fbc into /etc/modprobe.d/vfio.conf like so options vfio-pci ids=10de:1380,10de:0fbc. Next, add/modify the following line in /etc/mkinitcpio.conf with MODULES=" ... vfio vfio_iommu_type1 vfio_pci vfio_virqfd nvidia ... ". You may need to use nouveau or some other driver depending on your video card. In my case, i am using non-free nvidia drivers. Also, add/modify the line with HOOKS=" ... modconf ... "; however, more than likely you already have it somewhere in the HOOKS line anyhow. Now rebuild initramfs by calling mkinitcpio -g /boot/linux-custom.img and reboot.

Validate that your GPU, lspci -nnk, is using the vfio-pci as the kernel driver loader otherwise something was not done correctly.

02:00.0 VGA compatible controller [0300]: NVIDIA Corporation GM107 [GeForce GTX 750 Ti] [10de:1380] (rev a2)
    Subsystem: Gigabyte Technology Co., Ltd GM107 [GeForce GTX 750 Ti] [1458:362d]
    Kernel driver in use: vfio-pci
    Kernel modules: nouveau, nvidia_drm, nvidia
02:00.1 Audio device [0403]: NVIDIA Corporation Device [10de:0fbc] (rev a1)
    Subsystem: Gigabyte Technology Co., Ltd Device [1458:362d]
    Kernel driver in use: vfio-pci
    Kernel modules: snd_hda_intel

If the vfio-pci kernel driver is loaded for the GPU you can proceed by installing the following:

sudo pacman -S libvirt virt-manager qemu

I also prefer to install ovmf-git from the AUR repository instead of ovmf from extra. You may use

sudo pacman -S yay

and with yay install

yay ovmf-git

Now edit the ```/etc/libvirt/qemu.conf` file and add the path of OVMF firmware:

nvram = ["/usr/share/ovmf/ovmf_code_x64.bin:/usr/share/ovmf/ovmf_vars_x64.bin"]

in my case. We also need to start several services:

sudo systemctl start libvirtd.service 
sudo systemctl start virtlogd.socket
sudo systemctl enable libvirtd.service
sudo systemctl enable virtlogd.socket

Now install

sudo pacman -S virt-manager

and add yourself to the group

sudo usermod -a -G libvirt username

and finally launch virt-manager. I recommend launching virt-manager from your GUI interface rather than terminal as if you have python3 installed you will run into errors otherwise you can simply run virt-manager & in the background from the terminal.

Within virt-manager you may initiate the installation process for Windows or some other operating system.

For settings in virt-manager here are my suggestions for a i7:

  • CPUs
    • Current allocation: 8
    • Copy host CPU configuration
    • Manually set CPU topology
      • Sockets: 1
      • Cores: 4
      • Threads: 2
  • PCI devices for GPU/GPU-audio (via add hardware button)
  • Any dedicated USB devices (via add hardware button)
  • Memory (minimum 8192 miB)
  • SCSI (requires virtio-win drivers otherwise use SATA for your HDD)
  • add SATA CDROM with virt-io and windows iso file

Hopefully your virtual machine will boot windows and install flawlessly. With SCSI you need to install the virtio-win drivers at the start of the windows installation through the windows driver select option.