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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.[1]

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 allows you to explicitly target individual devices.

1) Blacklist Drivers

By running lspci -knn you can easily find out which drivers are being used for a device so you know what 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 know which devices to bind to.

# /etc/modprobe.d/blacklist.conf
+ blacklist i915
+ blacklist snd_hda_intel
+ blacklist amdgpu

# /etc/modprobe.d/vfio.conf
+ options vfio-pci ids=1002:67ff,1002:aae0,8086:3e92 disable_vga=1
2) Alias Devices

Using lspci -nn it is easy to find a devices B/D/F identifier and its vendor:device identifier. Theb 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
+
+ # AMD Radeon RX 560 (1002:67ff,1002:aae0)
+ alias pci:v00001002d000067FFsv00001458sd000022FFbc03sc00i00 vfio-pci
+ alias pci:v00001002d0000AAE0sv00001458sd0000AAE0bc04sc03i00 vfio-pci
+
+ options vfio-pci ids=1002:67ff,1002:aae0,8086:3e92 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

References

  1. https://null-src.com/posts/qemu-vfio-pci/post.php ↩︎

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