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¶

Command	Description
`ujust setup-virtualization`	Main virtualization setup
`ujust setup-virtualization virt-on`	Enable KVM/libvirt
`ujust setup-virtualization virt-off`	Disable KVM/libvirt
`ujust setup-virtualization vfio-on`	Enable VFIO passthrough
`ujust setup-virtualization vfio-off`	Disable VFIO passthrough
`ujust setup-virtualization kvmfr`	Setup Looking Glass
`ujust setup-virtualization usbhp-on`	Enable USB hotplug
`ujust setup-virtualization usbhp-off`	Disable USB hotplug

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¶

Host: Run looking-glass-client
VM: Run Looking Glass host service
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"