GPU Passthrough¶

Overview¶

Pass the AMD GPU directly to a VM for native graphics performance.

Display Model

The GPU will be owned by the VM. The host is managed over SSH.

Prerequisites¶

IOMMU enabled in BIOS (AMD-Vi)
GPU in its own IOMMU group
No host drivers attached to GPU

Enable IOMMU¶

Edit /etc/default/grub:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash amd_iommu=on iommu=pt"

Update GRUB:

sudo update-grub
sudo reboot

Verify IOMMU¶

dmesg | grep -i iommu

Look for "AMD-Vi" or "IOMMU enabled".

Find GPU IOMMU Group¶

#!/bin/bash
for d in /sys/kernel/iommu_groups/*/devices/*; do
    n=${d#*/iommu_groups/*}; n=${n%%/*}
    printf 'IOMMU Group %s ' "$n"
    lspci -nns "${d##*/}"
done | grep -i "vga\|audio"

Note the GPU and its audio device IDs (e.g., 1002:xxxx).

Bind GPU to VFIO¶

Create VFIO Configuration¶

# /etc/modprobe.d/vfio.conf
options vfio-pci ids=1002:xxxx,1002:yyyy

Replace with your GPU and audio device IDs.

Load VFIO Early¶

# /etc/modules-load.d/vfio.conf
vfio-pci
vfio
vfio_iommu_type1

Blacklist AMD Drivers¶

# /etc/modprobe.d/blacklist-amd.conf
blacklist amdgpu
blacklist radeon

Update Initramfs¶

sudo update-initramfs -u
sudo reboot

Verify VFIO Binding¶

lspci -nnk | grep -A3 "VGA"

Should show Kernel driver in use: vfio-pci.

Attach GPU to VM¶

In virt-manager or virsh:

Add PCI Host Device (GPU)
Add PCI Host Device (GPU Audio)
Remove virtual display (Spice/VNC)
Connect monitor to GPU HDMI

Troubleshooting¶

IOMMU Group Issues¶

If GPU shares a group with other devices:

Try different PCIe slots
Use ACS override patch (last resort)

Reset Issues¶

Some GPUs don't reset properly:

# /etc/modprobe.d/vfio.conf
options vfio-pci ids=1002:xxxx disable_vga=1

No Display After VM Start¶

Verify monitor connected to GPU
Check VM is using UEFI
Ensure Q35 chipset selected