iGPU Passthrough

Description

In this section we will be using GPU Passthrough to give one particular virtual machine exclusive use of the integrated GPU in the machine running our Proxmox server. We will also set up USB passthrough, allowing us to use the VM with physical monitors and USB peripherals as if it were running bare metal.

Criteria for our iGPU Passthrough setup

There are many variants of GPU passthrough. The end goal we want is:

  • Proxmox as the host, and a Windows 10 or 11 guest
  • Passthrough of the entire GPU (no virtualisation i.e. GPU splitting)
  • The GPU being passed through is an Intel iGPU
  • Full display output to a physical monitor

Why another guide?

There is a not-so-obvious catch to getting the above configuration to work. Getting the video output to work requires using an Intel Graphics driver dated 2019 or earlier - newer versions will result in Code 43 errors. Left to its own devices, Windows will automatically update the driver to the latest version, disabling your video output.

After some trial and error with which steps are actually required and what the most efficient order is to perform them, I've finally figured out a procedure that works reliably for myself.

tl;dr?

  1. Install Windows in the VM with network access disabled.
  2. Pre-load the 2019 drivers.
  3. Disable Windows Update from automatically updating drivers.
  4. Shutdown the VM.
  5. Change the VM config to passthrough the iGPU with OpRegion support.
  6. Start up the VM.

Detail Instructions

Preparing the Host

Enabling IOMMU in BIOS

The exact BIOS settings will depend on your specific motherboard, so I won't go through all the options. On my machine, the setting is named VT-d, which stands for "Intel® Virtualization Technology for Directed I/O".

Find the PCI Bus and Slot ID and Device ID

In the Proxmox CLI, run the following command to get the PCI bus, slot ID, and numeric device ID for your iGPU:

lspci -nn | grep VGA

You should see something like this:

00:02.0 VGA compatible controller [0300]: Intel Corporation HD Graphics 530 [8086:1912] (rev 06)

The first set of numbers (00:02.0) is the PCI bus, slot ID, and function ID. The last pair of hexadecimal characters (8086:1912) are the vendor and device ID, with 8086 being the vendor ID for Intel, and 1912 being the device ID for this particular iGPU.

Enable IOMMU in GRUB

Open the file /etc/default/grub, find the line starting with GRUB_CMDLINE_LINUX_DEFAULT, and append the flag intel_iommu=on to the end.

Before (example):

GRUB_CMDLINE_LINUX_DEFAULT="quiet"

After:

GRUB_CMDLINE_LINUX_DEFAULT="quiet intel_iommu=on"

Then apply the change by executing the below:

update-grub2

Update initramfs

Edit the file /etc/modprobe.d/vfio.conf so that it contains the following:

options vfio-pci ids=8086:3912
            softdep drm pre: vfio-pci

Then apply the change by executing the following:

update-initramfs -u -k all

Reboot your Proxmox host for the changes to take effect.

Linux Guest

I recommend first testing GPU Passthrough with a Linux VM as they have better iGPU passthrough support. This will eliminate any issues with your hardware or host configuration.

  • Download your ISO and store it in the local storage of your Proxmox node. I did this test using Pop!_OS by System76 as my distro.
  • Create a normal Linux VM.
    • Machine type i440fx and SeaBIOS bios.
    • Disks: enable Discard and SSD Emulation
    • CPU: Change Type to host, and increase Cores
  • Install the OS. Once you have a working desktop environment, shut down the VM.
  • In the Proxmox web UI, navigate to the VM, select Hardware from the list view, click the Add button, and select PCI Device.
  • Select the radio button Raw Device if it is present, then change the Device dropdown to the entry for your iGPU. The checkboxes can remain on their defaults.
  • Repeat the process for your USB Host Controller (or USB devices if you choose that method).
  • Start up the VM. You should have video output displaying once the VM has reached the User Login screen for your desktop environment.

Windows 10 Guest

Preparation

Before you start, you will need:

  • A Windows 10 ISO saved in local storage.
  • The Windows VirtIO drivers ISO saved in local storage.
  • Intel Graphics Drivers from 2019.
    • I've successfully used igfx_win10_100.7158 dated 2019/09/09.
    • You will need to get this inside the VM. You can passthrough a USB Flash Drive or USB External HDD, host it on a SMB/CIFS network share, or create an ISO image with the contents of the driver zip file.

VM Creation

  • Create a Windows 10 VM.
  • Set Machine type to i440fx and BIOS to SeaBios.
  • Network: enable the Disconnect checkbox to disable network access.
  • Start the VM and follow the setup wizard until you arrive on the desktop.

Desktop Configuration

  • Next, navigate to the Intel Graphics driver folder, and into the Graphics subfolder.. Then run the pnp-util command. This will take a while.
cd ~\Desktop\igfx\Graphics
            pnp-util -a iigd_dch.inf
  • Open an elevated command prompt and run the following command:
reg add "HKLM\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate" /f /v ExcludeWUDriversInQualityUpdate /t REG_DWORD /d 1
  • Shutdown the VM.

Adding iGPU Passthrough to the VM

  • In your Proxmox CLI, navigate to the folder storing your VM configuration files and open the .conf file for your VM, e.g. /etc/pve/nodes/comet/qemu-server/101.conf
  • Add the three following lines:
args: -device vfio-pci,host=00:02.0,x-igd-opregion=on,x-igd-gms=1
vga: none
  • The first line tells Proxmox to passthrough the iGPU device at ID 00:02.0. The opregion setting enable OpRegion support which enables physical video out. The gms setting allocates a small amount of RAM which seems to be necessary for OpRegion to work.
  • The second line disables the Proxmox standard virtualised display as it would occupy the same address in the VM as the iGPU, preventing the VM from starting.
  • Save and close the file.

Testing video output

  • Start up the VM. It should take a bit longer than usual as it will detect the presence of a new device and install the drivers. Once Windows gets to the User Login stage, you should have video output on your monitor.

Windows 11 Guest

VM Creation

  • The steps are similar to Windows 10. The main difference is that by default, Proxmox will default to the q35 machine type and a OVMFUEFI instead of i440fx and SeaBIOS. Windows 11 can work without UEFI and TPM, we just need to bypass it.
  • During VM creation, change the machine type to i440fx, the BIOS to SeaBIOS and disable TPM.
  • Start the VM

Windows Setup

  • During the first phase of the setup process, when it asks you which version of Windows you'd like to install, press Shift+F10 to open a command prompt.
  • Open regedit. Navigate to HKEY_LOCAL_MACHINE\SYSTEM\Setup and create a key (i.e. folder) named LabConfig.
  • Create two DWORD (32-bit) entries, one named BypassSecureBootCheck and the second named BypassTPMCheck. Set their values to 1.
  • Close regedit and the command prompt, and continue the installation.
  • The setup wizard should continue.
  • The rest of the steps are the same as for the Windows 10 VM.

Troubleshooting Tips

If you're having difficulty, here are some tips:

  • Enable Remote Desktop access (Win > Remote Desktop Settings) and note the IP address of the VM (Win > cmd > ipconfig).
  • If you enable Qemu Agent in the VM and install the guest client tools on the Windows VirtIO drivers CD (D:\virtio-win-guest-tools.exe) you'll be able to see the IP address of the Windows VM from Proxmox web UI and gracefully reboot/shutdown the VM.
  • You can enable local network access by setting the network card to use a valid static IP with an incorrect gateway. e.g.:
    • IP: 192.168.8.100
    • Mask: 255.255.255.0
    • Gateway: 192.168.8.199 (where there is no device using .199)
    • You can then disable the Disconnect checkbox in Proxmox which simulates the network cable being disconnected.
  • Make sure your C:\ drive is at least 48GB. Windows will use up over 32GB halfway through running Windows Updates.
  • Consider using Proxmox to take a snapshot of the VM once you've reached the desktop. If something goes wrong you can just restore the snapshot instead of going through Windows Setup again.
  • There are several settings you can change to improve the performance, such as using SCSI instead of IDE and playing with the Cache settings. These are general to VM creation and I have not covered them in here.