Table Of Contents

• IOMMU Setup
• Installing Packages
• Enabling Services
• Guest Setup
• Attching PCI Devices
• Libvirt Hooks
• Keyboard/Mouse Passthrough
• Video Card Virtualisation Detection
• Audio Passthrough
• GPU vBIOS Patching

Enable & Verify IOMMU

BIOS Settings
Enable Intel VT-d or AMD-Vi in BIOS settings.
If you can't find those virtualization options in BIOS, your hardware probably doesn't support it.

Disable Resizable BAR Support in BIOS settings. Cards that support Resizable BAR can cause problems with black screens following driver load if Resizable BAR is enabled in UEFI/BIOS. There doesn't seem to be a large performance penalty for disabling it, so turn it off for now until ReBAR support is available for KVM.

Set the kernel paramater depending on your CPU.
For GRUB user, edit grub configuration.

/etc/default/grub
GRUB_CMDLINE_LINUX_DEFAULT="... intel_iommu=on iommu=pt ..."
OR
GRUB_CMDLINE_LINUX_DEFAULT="... amd_iommu=on iommu=pt ..."

Generate grub.cfg

grub-mkconfig -o /boot/grub/grub.cfg

Reboot your system for the changes to take effect.

To verify IOMMU, run the following command.

dmesg | grep IOMMU

The output of above command should contain the following message:

Intel-IOMMU: enabled

or

AMD-Vi: AMD IOMMUv2 loaded and initialized

Now, you need to make sure that your IOMMU groups are valid.
Run the following script to view the IOMMU groups and attached devices. \

#!/bin/bash
shopt -s nullglob
for g in `find /sys/kernel/iommu_groups/* -maxdepth 0 -type d | sort -V`; do
    echo "IOMMU Group ${g##*/}:"
    for d in $g/devices/*; do
        echo -e "\t$(lspci -nns ${d##*/})"
    done;
done;

During passthrough, you need to pass every device (except PCI) in the group which includes your GPU.
You can avoid having to pass everything by using ACS override patch.

Install required tools

Gentoo Linux

RECOMMENDED USE FLAGS: app-emulation/virt-manager gtk
             app-emulation/qemu spice usb usbredir pulseaudio

emerge -av qemu virt-manager libvirt ebtables dnsmasq

Arch Linux

pacman -S qemu libvirt edk2-ovmf virt-manager dnsmasq ebtables

Fedora

dnf install @virtualization

Ubuntu

apt install qemu-kvm qemu-utils libvirt-daemon-system libvirt-clients bridge-utils virt-manager ovmf

Enable required services

SystemD

systemctl enable --now libvirtd

OpenRC

rc-update add libvirtd default
rc-service libvirtd start

Sometimes, you might need to start default network manually.

virsh net-start default
virsh net-autostart default

Setup Guest OS

NOTE: You should replace win10 with your VM's name where applicable
You should add your user to libvirt group to be able to run VM without root. And, input and kvm group for passing input devices.

usermod -aG kvm,input,libvirt username

Download virtio driver.
Launch virt-manager and create a new virtual machine. Select Customize before install on Final Step.
In Overview section, set Chipset to Q35, and Firmware to UEFI
In CPUs section, set CPU model to host-passthrough, and CPU Topology to whatever fits your system.
For SATA disk of VM, set Disk Bus to virtio.
In NIC section, set Device Model to virtio
Add Hardware > CDROM: virtio-win.iso
Now, Begin Installation. Windows can't detect the virtio disk, so you need to Load Driver and select virtio-iso/amd64/win10 when prompted.
After successful installation of Windows, install virtio drivers from virtio CDROM. You can then remove virtio iso.

Attaching PCI devices

Remove Channel Spice, Display Spice, Video QXL, Sound ich* and other unnecessary devices.
Now, click on Add Hardware, select PCI Devices and add the PCI Host devices for your GPU's VGA and HDMI Audio.

Libvirt Hooks

Libvirt hooks automate the process of running specific tasks during VM state change.
More info at: PassthroughPost

Note: Comment Unbind/rebind EFI framebuffer line from start and stop script if you're using AMD 6000 series cards, thanks to cdgriffith. Also, move the line to unload AMD kernal module below detaching devices from host. These might also apply to older AMD cards.

Create Libvirt Hook

mkdir /etc/libvirt/hooks
touch /etc/libvirt/hooks/qemu
chmod +x /etc/libvirt/hooks/qemu

/etc/libvirt/hooks/qemu

#!/bin/bash GUEST_NAME="$1" HOOK_NAME="$2" STATE_NAME="$3" MISC="${@:4}" BASEDIR="$(dirname $0)" HOOKPATH="$BASEDIR/qemu.d/$GUEST_NAME/$HOOK_NAME/$STATE_NAME" set -e # If a script exits with an error, we should as well. if [ -f "$HOOKPATH" ]; then eval \""$HOOKPATH"\" "$@" elif [ -d "$HOOKPATH" ]; then while read file; do eval \""$file"\" "$@" done <<< "$(find -L "$HOOKPATH" -maxdepth 1 -type f -executable -print;)" fi

Create Start Script

mkdir -p /etc/libvirt/hooks/qemu.d/win10/prepare/begin
touch /etc/libvirt/hooks/qemu.d/win10/prepare/begin/start.sh
chmod +x /etc/libvirt/hooks/qemu.d/win10/prepare/begin/start.sh

/etc/libvirt/hooks/qemu.d/win10/prepare/begin/start.sh

#!/bin/bash set -x # Stop display manager systemctl stop display-manager # rc-service xdm stop # Unbind VTconsoles: might not be needed echo 0 > /sys/class/vtconsole/vtcon0/bind echo 0 > /sys/class/vtconsole/vtcon1/bind # Unbind EFI Framebuffer echo efi-framebuffer.0 > /sys/bus/platform/drivers/efi-framebuffer/unbind # Unload NVIDIA kernel modules modprobe -r nvidia_drm nvidia_modeset nvidia_uvm nvidia # Unload AMD kernel module # modprobe -r amdgpu # Detach GPU devices from host # Use your GPU and HDMI Audio PCI host device virsh nodedev-detach pci_0000_01_00_0 virsh nodedev-detach pci_0000_01_00_1 # Load vfio module modprobe vfio-pci

Create Stop Script

mkdir -p /etc/libvirt/hooks/qemu.d/win10/release/end
touch /etc/libvirt/hooks/qemu.d/win10/release/end/stop.sh
chmod +x /etc/libvirt/hooks/qemu.d/win10/release/end/stop.sh

/etc/libvirt/hooks/qemu.d/win10/release/end/stop.sh

#!/bin/bash set -x # Attach GPU devices to host # Use your GPU and HDMI Audio PCI host device virsh nodedev-reattach pci_0000_01_00_0 virsh nodedev-reattach pci_0000_01_00_1 # Unload vfio module modprobe -r vfio-pci # Load AMD kernel module #modprobe amdgpu # Rebind framebuffer to host echo "efi-framebuffer.0" > /sys/bus/platform/drivers/efi-framebuffer/bind # Load NVIDIA kernel modules modprobe nvidia_drm modprobe nvidia_modeset modprobe nvidia_uvm modprobe nvidia # Bind VTconsoles: might not be needed echo 1 > /sys/class/vtconsole/vtcon0/bind echo 1 > /sys/class/vtconsole/vtcon1/bind # Restart Display Manager systemctl start display-manager # rc-service xdm start

Keyboard/Mouse Passthrough

In order to be able to use keyboard/mouse in the VM, you can either passthrough the USB Host device or use Evdev passthrough.

Using USB Host Device is simple,
Add Hardware > USB Host Device, add your keyboard and mouse device.

For Evdev passthrough, follow these steps:
Modify libvirt configuration of your VM.
Note: Save only after adding keyboard and mouse devices or the changes gets lost.
Change first line to:

virsh edit win10
<domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>

Find your keyboard and mouse devices in /dev/input/by-id. You'd generally use the devices ending with event-kbd and event-mouse. And the devices in your configuration right before closing </domain> tag.
Replace MOUSE_NAME and KEYBOARD_NAME with your device id.

virsh edit win10
... <qemu:commandline> <qemu:arg value='-object'/> <qemu:arg value='input-linux,id=mouse1,evdev=/dev/input/by-id/MOUSE_NAME'/> <qemu:arg value='-object'/> <qemu:arg value='input-linux,id=kbd1,evdev=/dev/input/by-id/KEYBOARD_NAME,grab_all=on,repeat=on'/> </qemu:commandline> </domain>

You need to include these devices in your qemu config.

/etc/libvirt/qemu.conf
... user = "YOUR_USERNAME" group = "kvm" ... cgroup_device_acl = [ "/dev/input/by-id/KEYBOARD_NAME", "/dev/input/by-id/MOUSE_NAME", "/dev/null", "/dev/full", "/dev/zero", "/dev/random", "/dev/urandom", "/dev/ptmx", "/dev/kvm", "/dev/kqemu", "/dev/rtc","/dev/hpet", "/dev/sev" ] ...

Also, switch from PS/2 devices to virtio devices. Add the devices inside <devices> block

virsh edit win10
... <devices> ... <input type='mouse' bus='virtio'/> <input type='keyboard' bus='virtio'/> ... </devices> ...

Audio Passthrough

VM's audio can be routed to the host. You need Pulseaudio. It's hit or miss.
You can also use Scream instead of Pulseaudio.
Modify the libvirt configuration of your VM.

virsh edit win10
... <qemu:commandline> ... <qemu:arg value="-device"/> <qemu:arg value="ich9-intel-hda,bus=pcie.0,addr=0x1b"/> <qemu:arg value="-device"/> <qemu:arg value="hda-micro,audiodev=hda"/> <qemu:arg value="-audiodev"/> <qemu:arg value="pa,id=hda,server=/run/user/1000/pulse/native"/> </qemu:commandline> </devices>

Video card driver virtualisation detection

Video Card drivers refuse to run in Virtual Machine, so you need to spoof Hyper-V Vendor ID.

virsh edit win10
... <features> ... <hyperv> ... <vendor_id state='on' value='whatever'/> ... </hyperv> ... </features> ...

NVIDIA guest drivers also require hiding the KVM CPU leaf:

virsh edit win10
... <features> ... <kvm> <hidden state='on'/> </kvm> ... </features> ...

vBIOS Patching

NOTE: You only need patch the dumped ROM file. You don't need to make changes on the hardware BIOS.
While most of the GPU can be passed with stock vBIOS, some GPU requires vBIOS patching depending on your host distro.
In order to patch vBIOS, you need to first dump the GPU vBIOS from your system.
If you have Windows installed, you can use GPU-Z to dump vBIOS.
To dump vBIOS on Linux, you can use following command (replace PCI id with yours):
If it doesn't work on your distro, you can try using live cd.

echo 1 > /sys/bus/pci/devices/0000:01:00.0/rom
cat /sys/bus/pci/devices/0000:01:00.0/rom > path/to/dump/vbios.rom
echo 0 > /sys/bus/pci/devices/0000:01:00.0/rom

To patch vBIOS, you need to use Hex Editor (eg., Okteta) and trim unnecessary header.
For NVIDIA GPU, using hex editor, search string “VIDEO”, and remove everything before HEX value 55.
This is probably the same for AMD device.

To use patched vBIOS, edit VM's configuration to include patched vBIOS inside hostdev block of VGA

virsh edit win10
... <hostdev mode='subsystem' type='pci' managed='yes'> <source> ... </source> <rom file='/home/me/patched.rom'/> ... </hostdev> ...

See Also

Single GPU Passthrough Troubleshooting
Single GPU Passthrough by joeknock90
Single GPU Passthrough by YuriAlek
Single GPU Passthrough by wabulu
ArchLinux PCI Passthrough
Gentoo GPU Passthrough