Virtualization - Bazzite GPU Passthrough & KVM

Overview

Advanced virtualization features for Bazzite including KVM, VFIO GPU passthrough, Looking Glass (kvmfr), and USB hotplug for VMs.

Quick Reference

KVM/Libvirt

Enable Virtualization

# Enable KVM and libvirt
ujust setup-virtualization virt-on

Enables:

• libvirtd service
• User permissions for VMs
• Default network
• QEMU/KVM backend

Disable Virtualization

# Disable KVM and libvirt
ujust setup-virtualization virt-off

VFIO GPU Passthrough

Enable VFIO

# Enable VFIO for GPU passthrough
ujust setup-virtualization vfio-on

What VFIO does:

• Isolates GPU from host
• Passes GPU directly to VM
• Near-native GPU performance in VM

Requirements:

• Two GPUs (or iGPU + dGPU)
• IOMMU support (VT-d or AMD-Vi)
• Supported GPU

Disable VFIO

# Disable VFIO passthrough
ujust setup-virtualization vfio-off

Returns GPU to host control.

Looking Glass (kvmfr)

Setup kvmfr

# Setup Looking Glass shared memory
ujust setup-virtualization kvmfr

Looking Glass:

• Zero-copy GPU framebuffer sharing
• Near-zero latency display
• No GPU encoding needed
• Mouse/keyboard passthrough

Requirements:

• Windows VM with GPU passthrough
• Looking Glass host app
• IVSHMEM device in VM

Using Looking Glass

1. Host: Run looking-glass-client
2. VM: Run Looking Glass host service
3. Connect via shared memory

USB Hotplug

Enable USB Hotplug

# Enable USB device hotplug for VMs
ujust setup-virtualization usbhp-on

Allows:

• Hot-add USB devices to running VMs
• Dynamic USB device assignment
• No VM restart needed

Disable USB Hotplug

ujust setup-virtualization usbhp-off

Common Workflows

Basic VM Setup

# Enable virtualization
ujust setup-virtualization virt-on

# Use virt-manager for GUI
virt-manager

Gaming VM with GPU Passthrough

# 1. Enable VFIO
ujust setup-virtualization vfio-on

# 2. Reboot (GPU now isolated)
systemctl reboot

# 3. Create VM with GPU
# In virt-manager: Add PCI device (GPU)

# 4. Optional: Setup Looking Glass
ujust setup-virtualization kvmfr

Dynamic USB Access

# Enable USB hotplug
ujust setup-virtualization usbhp-on

# In running VM:
# - Right-click VM in virt-manager
# - Add Hardware > USB Host Device
# - Select device

IOMMU Groups

Check IOMMU

# Verify IOMMU enabled
dmesg | grep -i iommu

# List 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

GPU IOMMU Group

# Find GPU group
lspci -nn | grep -i nvidia
# or
lspci -nn | grep -i amd

Ideal: GPU alone in IOMMU group. If not, may need ACS override patch.

VM Management

Virsh Commands

# List VMs
virsh list --all

# Start VM
virsh start <vm-name>

# Shutdown VM
virsh shutdown <vm-name>

# Force off
virsh destroy <vm-name>

GUI Management

# virt-manager (GUI)
virt-manager

# GNOME Boxes (simpler)
gnome-boxes

Troubleshooting

VFIO Not Binding GPU

Check IOMMU:

dmesg | grep -i iommu
# Should show "IOMMU enabled"

Enable in BIOS:

• Intel: VT-d
• AMD: AMD-Vi / IOMMU

Check binding:

lspci -nnk | grep -A3 "VGA\|Audio"
# Kernel driver should be vfio-pci

Looking Glass Black Screen

Check IVSHMEM:

# In VM, verify IVSHMEM device exists
# Check Looking Glass host logs

Verify shared memory:

ls -la /dev/shm/looking-glass

USB Device Not Passing Through

Check permissions:

# User in libvirt group?
groups $USER

Check device:

lsusb
# Identify device ID

VM Won't Start After VFIO

GPU still attached to host:

# Verify VFIO binding
lspci -nnk | grep -A3 "VGA"
# Should show: Kernel driver in use: vfio-pci

Reboot may be needed after vfio-on.

Cross-References

• bazzite-ai:vm - QCOW2 VM management
• bazzite:gpu - GPU driver configuration
• bazzite-ai:configure - libvirtd service

When to Use This Skill

Use when the user asks about:

• "GPU passthrough", "VFIO", "pass GPU to VM"
• "Looking Glass", "kvmfr", "VM display"
• "KVM", "libvirt", "virtualization"
• "USB hotplug", "pass USB to VM"
• "gaming VM", "Windows VM", "VM performance"
• "IOMMU", "VT-d", "AMD-Vi"