I spent a really long time trying to get this working recently, so I figured I'd document what I did to get GPU passthrough working on my laptop. The steps I went through might be a bit different on other distros given that I am using Proxmox, but the broad strokes should apply. Bear in mind, this is with regards to using a Windows 11 virtual machine. Certain steps may be different or unnecessary for Linux-based virtual machines.
First, why might you want to do this? Well, the most obvious reason is that virtual machines are slooow. So, by passing through a GPU you can improve its speed considerably. Another possibility would be that you want to use the GPU for some task like GPU transcoding for Plex, or to simply use it as a render host, or you may want to use it for something like AI workloads that rely on the GPU. Alternatively, you may just want to use this to have a virtual machine that you can host Steam on or something like that (bear in mind, some games and applications will not run under virtual machines or run if you are using Remote Desktop).
0. Enable Virtualization-specifi
c settings in the BIOS such as Intel VT-x and VT-d or AMD IOMMU and AMD-V, and disable Safe Boot (After installing your OS of choice if it requires UEFI)
1. Create a virtual machine
- BIOS should be OVMF (UEFI)
- Machine type should be q35
- SCSI Controller should be VirtIO SCSI or SCSI Single; others may work these are just what I have tested
- Display should be VirtIO-GPU (virtio); other display emulators will not work for Proxmox's built-in console VNC, or otherwise cause the VM to crash on launch.
- CPU may need to be of type host and hidden from the VM
2. Edit GRUB config line beginning with "GRUB_CMDLINE_LINUX_DEFAULT"
- These settings worked for me: "quiet intel_iommu=on iommu=pt pcie_acs_override=downstream,multifunction nofb nomodeset"
- For AMD CPUs, change 'intel_iommu' to 'amd_iommu'
- Save the changes and then run 'update-grub'
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