PCI Passthrough
Ensure IOMMU Is Activated
First step of this process is to make sure that your hardware is even capable of this type of virtualization. You need to have a motherboard, CPU, and BIOS that has an IOMMU controller and supports Intel-VT-x and Intel-VT-d or AMD-v and AMD-vi. Some motherboards use different terminology for these, for example they may list AMD-v as SVM and AMD-vi as IOMMU controller.
Ensure Kernel Modules
Debian
# /etc/modules
# /etc/modules: kernel modules to load at boot time.
#
# This file contains the names of kernel modules that should be loaded
# at boot time, one per line. Lines beginning with "#" are ignored.
+ vfio_pci
+ vfio
+ vfio_iommu_type1
+ vfio_virqfd
Bind vfio-pci Driver to Devices
Now you can bind the vfio-pci driver to your devices at startup so they can be passed through to a VM. There are two ways of doing this, the first way is quick and easy but forces you to blacklist an entire driver which would stop you from being able to use that driver for another device that you aren't passing through. The second way is a little more complciated but allows you to target individual devices without blacklisting an entire driver.
1) Blacklist Drivers
By running lspci -knn you can easily find out which drivers are being used for a device so you know what driver to blacklist in addition to their <vendor>:<device> identifier. Armed with both of these we can blacklist the drivers we don't want being used and let the vfio-pci driver know which device(s) to bind to.
Below is an example of blacklisting the driver i915 (Intel iGPU driver) so I can pass through my iGPU to a virtual machine. The driver is blacklisted so it won't load and the device identified by <vendor>:<device> is added as a parameter to the vfio-pci driver so it knows which device to bind with.
# /etc/modprobe.d/blacklist.conf
+ blacklist i915
# /etc/modprobe.d/vfio.conf
+ options vfio-pci ids=8086:3e92 disable_vga=1
2) Alias Devices
Using lspci -knn it is easy to find a devices B/D/F identifier and its <vendor>:<device> identifier. Then we can find its modalias by running cat /sys/bus/pci/devices/<B/D/F>/modalias. Armed with both of these we can let the vfio-pci module know which devices to bind to.
# /etc/modprobe.d/vfio.conf
+ # Intel UHD 630 (8086:3e92)
+ alias pci:v00008086d00003E92sv00001458sd0000D000bc03sc80i00 vfio-pci
+
+ options vfio-pci ids=8086:3e92 disable_vga=1
Rebuild initramfs
Debian
update-initramfs -u
Update Bootloader
Update Kernel Parameters
Grub2
# /etc/default/grub
- GRUB_CMDLINE_LINUX_DEFAULT="quiet"
+ GRUB_CMDLINE_LINUX_DEFAULT="quiet intel_iommu=igfx_off iommu=pt video=efifb:off"
Systemd
# /etc/kernel/cmdline
- root=ZFS=rpool/ROOT/pve-1 boot=zfs
+ root=ZFS=rpool/ROOT/pve-1 boot=zfs intel_iommu=igfx_off iommu=pt video=efifb:off
Rebuild Bootloader Options
Grub
update-grub
systemd-boot
bootctl update
Proxmox
pve-efiboot-tool refresh
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