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GPU passthrough to a Windows VM: what it can and cannot measure

Verified 2 min read

Plan a PVE GPU passthrough Windows VM, understand IOMMU/vfio/vBIOS issues, and separate VM results from bare-metal performance.

Tested onPro (26H2) · Build 26300.9457 · x64
E1
Build
26300.9457
Edition
Pro (26H2)
Architecture
x64
Support
Documentation (E1)
Evidence
E1Official documentation
Verified
2026-10-28
Page type
Lab

The short answer

Section titled “The short answer”

GPU passthrough gives a VM a real GPU via VFIO. It is excellent for testing drivers, UI, tuning and many games. It is not a bare-metal benchmark machine:

  • CPU overhead and VM exits remain;
  • display path/capture can add latency;
  • some anti-cheat and DRM refuse a VM;
  • vendor drivers may detect/limit virtualisation;
  • single-GPU hosts need special handling.

Use VM results as M-V, not as an absolute FPS claim.

What you need

Section titled “What you need”
Requirement Why
IOMMU enabled (VT-d/AMD-Vi) Isolates the GPU
ACS / clean IOMMU groups The GPU must be isolated from the host
vfio-pci binding Host must not claim the GPU
GPU vBIOS / reset support Some cards need a ROM or reset workaround
Second GPU or iGPU Host needs a display if the GPU is passed through
PVE hostpci config Attach the device to the VM
Windows VM (q35/OVMF) Matching the GPU driver stack

Outline

Section titled “Outline”
  1. Enable IOMMU in firmware and the kernel command line.
  2. Confirm IOMMU groups: find /sys/kernel/iommu_groups/ -type l.
  3. Blacklist the host driver and bind vfio-pci to the GPU/audio function.
  4. Add the PCI device to the VM (hostpci0), with PCIe/ROM options as needed.
  5. Install the vendor driver in Windows.
  6. Verify with Device Manager and nvidia-smi/Adrenalin/Arc Control.
  7. Test a known workload and record the VM configuration.

Do not copy a hostpci line from a forum without checking your IOMMU group and device IDs. Passing the GPU without its audio function or with the wrong ROM can produce a black screen.

What can be measured

Section titled “What can be measured”
Question VM result useful? Caveat
Does the driver install? Yes Driver may behave differently in a VM
Does the game launch? Yes Anti-cheat may block
Relative driver/setting changes Yes, with M-V label Same VM, same host
Absolute FPS vs bare metal No, not directly CPU/VM overhead, display path
Latency Careful Capture/display adds error
Battery/thermal No Not representative

Anti-cheat and licensing

Section titled “Anti-cheat and licensing”

Some anti-cheat systems treat a VM as an untrusted environment. Some NVIDIA/AMD driver features or licensing terms restrict virtualisation. Check the vendor and game terms; do not try to hide the VM from anti-cheat.

Safer test design

Section titled “Safer test design”
  • Use a second GPU for the host, or a headless host with IPMI/serial.
  • Keep a known-good snapshot before changing vfio/hostpci.
  • Record the exact host GPU, vBIOS, PVE version and VM config.
  • Compare only runs on the same VM and host.
  • If a result matters for a buying decision, validate on physical hardware.

Sources