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Looking Glass B7 — GPU Passthrough Attempt

Looking Glass B7 — GPU Passthrough Attempt

Prerequisite: This guide assumes you already have a working Windows 11 VM set up with virt-manager. If not, follow the VM Setup Guide first.

TL;DR: Looking Glass does not work on the ASUS ROG Zephyrus G16 GA605WV. The fundamental limitation is that the RTX 4060 has no display outputs — all physical ports (HDMI, USB-C) are routed through the AMD iGPU. Windows therefore cannot find a “valid output device” for frame capture. This document describes all steps performed and why it failed, as a reference for others.

What is Looking Glass?

Looking Glass is an open-source project that allows you to use a GPU-passthrough Windows VM without a physical monitor attached to the dGPU. The Windows VM gets the real GPU assigned and the rendered image is streamed to the Linux host via shared memory (IVSHMEM). The result is near-native GPU performance in a VM, visible in a window on your Linux desktop.

Requirements for operation:

  • dGPU with direct display output (DisplayPort, HDMI) — or a virtual display dongle
  • IOMMU isolation of the dGPU from the rest of the system
  • KVMFR kernel module on the host
  • Looking Glass host application in the Windows VM

System Configuration:

  • Model: ASUS ROG Zephyrus G16 GA605WV (2024)
  • CPU: AMD Ryzen AI 9 HX 370
  • iGPU: AMD Radeon 890M — card0, renderD128
  • dGPU: NVIDIA GeForce RTX 4060 Mobile — card1, renderD129
  • OS: Fedora 43, kernel 6.18.9
  • Secure Boot: Enabled
  • VM: Windows 11 (AtlasOS 0.5.0)

Phase 1 — Setting up IOMMU and VFIO

Checking IOMMU groups 

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 -E "NVIDIA|AMD|10de|1002" | head -20

The RTX 4060 was in a clean separate group:

IOMMU Group 20: 65:00.0 VGA [10de:28e0] NVIDIA GeForce RTX 4060 Max-Q
IOMMU Group 20: 65:00.1 Audio [10de:22be] NVIDIA HD Audio
IOMMU Group 21: 66:00.0 Display [1002:150e] AMD Radeon 890M

Setting VFIO kernel parameters 

sudo grubby --update-kernel=ALL \
  --args="vfio-pci.ids=10de:28e0,10de:22be \
          rd.driver.pre=vfio-pci \
          iommu=1 \
          rd.driver.blacklist=nouveau,nova_core \
          modprobe.blacklist=nouveau,nova_core \
          amdgpu.dcdebugmask=0x600"

Creating VFIO configuration files

/etc/modprobe.d/vfio.conf:

options vfio-pci ids=10de:28e0,10de:22be
softdep nvidia pre: vfio-pci
softdep nvidia_drm pre: vfio-pci
softdep nvidia_modeset pre: vfio-pci
softdep nouveau pre: vfio-pci

/etc/dracut.conf.d/vfio.conf:

add_drivers+=" vfio vfio_iommu_type1 vfio_pci "

Disabling nvidia-fallback.service

With VFIO, vfio-pci claims the GPU before the NVIDIA driver, causing nvidia-fallback.service to produce errors:

sudo systemctl disable nvidia-fallback.service
sudo systemctl mask nvidia-fallback.service

Rebuilding initramfs and rebooting 

sudo dracut --force
sudo reboot

Verification after reboot 

lspci -nnk -d 10de:28e0
# Expected: Kernel driver in use: vfio-pci

lspci -nnk -d 1002:150e
# Expected: Kernel driver in use: amdgpu

nvidia-smi
# Expected: NVIDIA-SMI has failed because... (normal with VFIO)

Phase 2 — Installing KVMFR kernel module

The KVMFR module provides the /dev/kvmfr0 interface for the IVSHMEM shared memory buffer.

Building and installing the module via DKMS 

cd ~/source/looking-glass-B7/module
sudo dkms install .

MOK enrollment for Secure Boot 

sudo mokutil --import /var/lib/dkms/mok.pub
# Set a temporary password
sudo reboot
# At reboot: Enroll MOK → Continue → Yes → password → reboot

Automatically loading and configuring the module 

echo "kvmfr" | sudo tee /etc/modules-load.d/kvmfr.conf

echo "options kvmfr static_size_mb=128" | sudo tee /etc/modprobe.d/kvmfr.conf

Setting udev permissions 

echo 'SUBSYSTEM=="kvmfr", OWNER="sten", GROUP="kvm", MODE="0660"' | \
  sudo tee /etc/udev/rules.d/99-kvmfr.rules

sudo udevadm control --reload-rules
sudo udevadm trigger

Manually loading and testing the module 

sudo modprobe -r kvmfr
sudo modprobe kvmfr

ls -la /dev/kvmfr0
# Expected: crw-rw---- 1 sten kvm 508, 0 ...

# If permissions are still incorrect after udev:
sudo chown sten:kvm /dev/kvmfr0
sudo chmod 660 /dev/kvmfr0

Phase 3 — Building the Looking Glass client

Downloading the source 

mkdir -p ~/source
cd ~/source
git clone https://github.com/gnif/LookingGlass.git looking-glass-B7
cd looking-glass-B7
git submodule update --init --recursive

Installing dependencies

The dependencies had to be discovered one by one. The complete list for Fedora 43:

sudo dnf install cmake gcc gcc-c++ libglvnd-devel fontconfig-devel \
  spice-protocol wayland-devel wayland-protocols-devel pipewire-devel \
  libxkbcommon-devel libsamplerate-devel libudev-devel nettle-devel \
  desktop-file-utils libXi-devel libXfixes-devel libXScrnSaver-devel \
  libXinerama-devel libXcursor-devel libXpresent-devel libXrandr-devel \
  libdecor-devel pulseaudio-libs-devel binutils-devel

Missing packages per build error:

ErrorMissing package
wayland-client.h: No such filewayland-devel
xkbcommon.h: No such filelibxkbcommon-devel
samplerate.h: No such filelibsamplerate-devel
Xi.h: No such filelibXi-devel
Xfixes.h: No such filelibXfixes-devel
bfd.h: No such filebinutils-devel
Xrandr.h: No such filelibXrandr-devel

Building and installing 

cd ~/source/looking-glass-B7/client
mkdir build && cd build
cmake ../
make -j$(nproc)
sudo make install
# Installs to /usr/local/bin/looking-glass-client

Verification 

which looking-glass-client
looking-glass-client --version
# Output: Looking Glass (B7), CPU: AMD Ryzen AI 9 HX 370 w/ Radeon 890M

Phase 4 — Modifying the VM XML

Changes via sudo virsh edit win11:

SPICE — Disable GL (input/clipboard only):

<graphics type="spice">
  <listen type="none"/>
  <image compression="off"/>
  <streaming mode="filter"/>
  <gl enable="no"/>
</graphics>

Video — Looking Glass replaces the display:

<video>
  <model type="none"/>
</video>

Note: With type="none", virt-manager shows a blank screen. This is expected. Temporarily switch back to type="vga" if you need Windows access during setup.

RTX 4060 PCI passthrough:

<hostdev mode="subsystem" type="pci" managed="yes">
  <source>
    <address domain="0x0000" bus="0x65" slot="0x00" function="0x0"/>
  </source>
</hostdev>
<hostdev mode="subsystem" type="pci" managed="yes">
  <source>
    <address domain="0x0000" bus="0x65" slot="0x00" function="0x1"/>
  </source>
</hostdev>

IVSHMEM buffer:

<shmem name="looking-glass">
  <model type="ivshmem-plain"/>
  <size unit="M">128</size>
</shmem>

Phase 5 — Installing the Looking Glass host in Windows

Temporarily restoring VGA access 

sudo virsh edit win11
# Change: <model type="none"/> to <model type="vga"/>
sudo virsh destroy win11
sudo virsh start win11

Host installer in Windows

This automatically installs the IVSHMEM driver and the Looking Glass Host service.

Installing the NVIDIA driver in Windows

The RTX 4060 showed up as “Microsoft Basic Display Adapter”. Download the driver from https://www.nvidia.com/drivers and install it.

Setting video back to none 

sudo virsh edit win11
# Change: <model type="vga"/> back to <model type="none"/>
sudo virsh destroy win11
sudo virsh start win11

Phase 6 — Connecting the client

Checking shared memory permissions 

ls -la /dev/kvmfr0

# QEMU fallback:
ls -la /dev/shm/looking-glass
sudo chown sten:kvm /dev/shm/looking-glass  # if permissions are incorrect

Starting the client 

looking-glass-client -s

Result: “Host Application Not Running” — shared memory works, but the host is not sending frames.

Why it failed

Host application log

C:\ProgramData\Looking Glass (host)\looking-glass-host.txt:

[I] d12.c | Not using unsupported adapter: Microsoft Basic Render Driver
[E] d12.c | Failed to locate a valid output device
[I] dxgi.c | Not using unsupported adapter: Microsoft Basic Render Driver
[E] dxgi.c | Failed to locate a valid output device
[E] app.c | Failed to find a supported capture interface

Diagnosis via PowerShell in Windows 

Get-PnpDevice | Where-Object {
    $_.FriendlyName -like "*NVIDIA*" -or $_.FriendlyName -like "*display*"
} | Format-Table FriendlyName, Status, Class

# Result:
# NVIDIA GeForce RTX 4060 Laptop GPU  OK  Display
# Microsoft Basic Display Adapter     OK  Display

The RTX 4060 was recognized and the driver was installed — but the host could not use it because there is no display output.

The fundamental hardware limitation

Confirmed via ls /sys/class/drm/:

card0-HDMI-A-1      ← HDMI is on AMD iGPU (card0)
card0-eDP-2         ← internal display via AMD (Dynamic MUX mode)
card1-DP-1 to DP-8  ← NVIDIA virtual outputs (no physical connectors)
card1-eDP-1         ← internal display via NVIDIA (dGPU MUX mode)

All physical ports on this laptop are on the AMD iGPU. The RTX 4060 has no physical display connectors whatsoever. DirectX 12 and DXGI require an active display output for frame capture — this is physically impossible on this laptop.

Additional findings

nvidia-fallback.service

Produces errors when VFIO is active. Solution: mask it (see Phase 1). When reverting, restore it:

sudo systemctl unmask nvidia-fallback.service
sudo systemctl enable nvidia-fallback.service

Samsung S24U monitor USB hub errors

Repeated dmesg errors when using the Samsung S24U via USB-C:

usb 5-1: device not accepting address, error -71

Not related to VM or GPU passthrough — built-in USB hub of the monitor.

QEMU shared memory fallback

If /dev/kvmfr0 is not available, QEMU uses /dev/shm/looking-glass (128MB, owned by qemu:qemu). The client falls back to this automatically.

Reverting everything 

# Restore kernel parameters
sudo grubby --update-kernel=ALL \
  --remove-args="vfio-pci.ids=10de:28e0,10de:22be rd.driver.pre=vfio-pci \
                 rd.driver.blacklist=nouveau,nova_core modprobe.blacklist=nouveau,nova_core" \
  --args="nvidia-drm.modeset=1 nvidia-drm.fbdev=1 \
          nvidia.NVreg_PreserveVideoMemoryAllocations=1 iommu=pt"

# Remove VFIO config
sudo rm /etc/modprobe.d/vfio.conf
sudo rm /etc/dracut.conf.d/vfio.conf
sudo rm /etc/modules-load.d/kvmfr.conf
sudo rm /etc/udev/rules.d/99-kvmfr.rules
sudo rm /etc/modprobe.d/kvmfr.conf

# Restore nvidia-fallback
sudo systemctl unmask nvidia-fallback.service
sudo systemctl enable nvidia-fallback.service

# Remove KVMFR DKMS module
sudo dkms remove kvmfr/0.0.12 --all

# Remove DKMS MOK key (optional)
sudo mokutil --delete /var/lib/dkms/mok.pub
# Set password for the MOK prompt at reboot

# Rebuild initramfs
sudo akmods --force
sudo dracut --force

sudo reboot
# At reboot: blue MOK screen → Delete MOK → password → reboot

Restore VM XML via sudo virsh edit win11: remove the two <hostdev> blocks and the <shmem> block, set video back to type="virtio" with accel3d="yes", and set SPICE back to gl enable="yes" rendernode="/dev/dri/by-path/pci-0000:66:00.0-render".

Conclusion

Looking Glass is an impressive project but requires hardware that is simply not present on the Zephyrus G16. For Windows applications on this laptop, the best options are:

References

YubiKey 5C NFCasusctl & ROG Control Center