### **Enable IOMMU**
***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***
```sh
grub-mkconfig -o /boot/grub/grub.cfg
```
Reboot your system for the changes to take effect.
### **Verify IOMMU**
***If you don't see any output when running following command, IOMMU is not functioning.***
```sh
dmesg | grep 'IOMMU enabled'
```
### **Install required tools**
Gentoo Linux
```sh
emerge -av qemu virt-manager libvirt ebtables dnsmasq
```
Arch Linux
```sh
pacman -S qemu libvirt edk2-ovmf virt-manager dnsmasq ebtables
```
Fedora
```sh
dnf install @virtualization
```
### **Enable required services**
SystemD
```sh
systemctl enable --now libvirtd
```
OpenRC
```sh
rc-update add libvirtd default
rc-service libvirtd start
```
Sometimes, you might need to start default network manually.
```sh
virsh net-start default
virsh net-autostart default
```
### **Setup Guest OS**
***NOTE: You should replace win10 with your VM's name where applicable*** \
Download [virtio](https://fedorapeople.org/groups/virt/virtio-win/direct-downloads/stable-virtio/virtio-win.iso) 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.
### **Attaching PCI devices**
Remove Channel Spice, Display Spice, Video XQL, 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 \
Some GPU vBIOS needs to be patched for UEFI Support. \
***----- TODO: vBIOS patching ------*** \
To use patched vBIOS, edit VM's configuration to include patched vBIOS inside ***hostdev*** block of VGA
```sh
mkdir /etc/libvirt/hooks
touch /etc/libvirt/hooks/qemu
chmod +x /etc/libvirt/hooks/qemu
```
virsh edit win10
```xml
...
...
...
```
### Libvirt Hooks
Libvirt hooks automate the process of running specific tasks during VM state change. \
More info at: [PassthroughPost](https://passthroughpo.st/simple-per-vm-libvirt-hooks-with-the-vfio-tools-hook-helper/)
Create Libvirt Hook
```sh
mkdir /etc/libvirt/hooks
touch /etc/libvirt/hooks/qemu
chmod +x /etc/libvirt/hooks/qemu
```
/etc/libvirt/hooks/qemu
```sh
#!/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
```
### Keyboard/Mouse Passthrough
Modify libvirt configuration of your VM. Change first line to:
virsh edit win10
```xml
```
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 `` tag. \
Replace ***MOUSE_NAME*** and ***KEYBOARD_NAME*** with your device id.
virsh edit win10
```xml
...
```
You need to include these devices in your qemu config.
Also, switch from PS/2 devices to virtio devices. Add the devices inside ****** block
virsh edit win10
```xml
...
...
...
...
```
### **Audio Passthrough**
VM's audio can be routed to the host. You need ***Pulseaudio***. \
Modify the libvirt configuration of your VM.
virsh edit win10
```xml
...
...
```
### 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
```xml
...
...
...
...
...
...
```
Nvidia guest drivers also require hiding the KVM CPU leaf:
virsh edit win10
```xml
...
...
...
...
```
### User Groups
You should add your user to ***input***, ***kvm***, and ***libvirt*** groups.
```sh
usermod -aG kvm,input,libvirt username
```
### **See Also**
> [Single GPU Passthrough by joeknock90](https://github.com/joeknock90/Single-GPU-Passthrough)
> [Single GPU Passthrough by YuriAlek](https://gitlab.com/YuriAlek/vfio)
> [ArchLinux PCI Passthrough](https://wiki.archlinux.org/index.php/PCI_passthrough_via_OVMF)
> [Gentoo GPU Passthrough](https://wiki.gentoo.org/wiki/GPU_passthrough_with_libvirt_qemu_kvm)