Troubleshooting – Known issues, bugs and common quirks of KVM QEMU virtual machines with gpu passthrough

Hardware

Error “Unknown PCI header type ‘127’ “

Attention! The ASUS Prime x370/x470/x570 pro BIOS versions for AMD RYZEN 3000-series support (version 4602 – version 5220), will break a PCI passthrough setup. Error “Unknown PCI header type ‘127’“.

BIOS versions up to (and including) 4406, 2019/03/11 are working.

BIOS versions from (and including) 5406, 2019/11/25 are working.

Host OS

Kernel versions

Attention! A kernel version of 4.15 or higher is recommended for an AMD Ryzen passthrough setup. Kernel versions before 4.15 have a bug in NPT support, which results in bad performance.

Attention! Kernel version 5.1 and 5.2 (including all subversions) should not be used for a passthrough setup. Using these Kernel version results in massive program/game instability and crashes.

Guest OS 

Windows 10

Attention! Windows releases >=1803 require the Host to havekvm ignore_msrs=1 enabled, otherwise BSOD occur.

Windows 10 1903

Attention! Do not use 6ch/9ch audio devices in the virtual machine. It creates awful stuttering and performance loss. Use ac97 audio devices instead.

Error code 43 for passed Nvidia GPUs

The Nvidia driver throws Error Code 43, if it recognizes the GPU is being passed through to a virtual machine. I wrote an separate article on that matter.

Sound errors

After some sleepless nights I wrote an separate article on that matter.

KVM / QEMU

QEMU 4.0 with Q35

Attention! Starting with QEMU version 4.0, virtual machines with q35 chip will require <ioapic driver='kvm'/> under <features> tag in the libvirt configuration (respectively kernel_irqchip=on as QEMU-machine arg).