AMD iGPU passthrough attempt

User Support General
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Damn this post and the linked/related ones are a great way to understand how things work under the hood ! ^^

Just a noob remark, have you tried by blacklisting amdgpu in dom0 and assigning the device to xen-pciback ? I read nowhere that you tried it.
This would prevent dom0 and/or the driver from doing nasty things with your GPU before PT-ing !

Below is my working method for a RX580, maybe that works for you too ?

Some notes before
  • I know the RX580 is not a iGPU, and I’m using it in a Ryzen desktop CPU (Ryzen 1700X), and there are many things I don’t know, but this method may be of help to others
  • the RX580 card has no FLR, is on the primary x16 PCI slot, so it’s used for displaying BIOS POST and early kernel messages, then xen-pciback seizes it, and the display switches to my other GPU, fortunately an Nvidia (so no driver conflict).
  • those instructions are for a Debian-based dom0, please carefully adapt. I just started Qubes, so I don’t know the correct paths and don’t wanna say 5h!t ! ^^
  • the RX580 must NEVER leave the pci-assignable pool, or hell will fall on you.

Steps

1. Modules config

  • First ensure that /etc/modules or modprobe.d/ contains this
    (PS: it’s already done on Qubes, in /etc/sysconfig/modules/qubes-dom0.modules)
xen-pciback
  • In /etc/modprobe.d/atigpu-blacklist.conf (for Qubes /etc/sysconfig/modules/atigpu-blacklist.conf seems the right place)
blacklist amdgpu

As you also have an AMD dGPU, I think you need an extra step to reload the driver once the domU containing the iGPU is started, but I’ve not tested it : my setup uses a Nvidia GPU for dom0, so it’s easier.

2. initramfs config

  • Create a new script like /usr/share/initramfs-tools/scripts/init-top/zload_xen-pciback, and don’t forget to chmod +x zload_xen-pciback, it’s a sh script.
    PS: no idea where this script should be in Qubes !
#!/bin/sh
modprobe xen-pciback hide=\(0000:25:00.0\)\(0000:25:00.1\)
  • In /usr/share/initramfs-tools/scripts/init-top/udev
    PS: no idea where this script should be in Qubes !
# change
PREREQS=""
# to
PREREQS="zload_xen-pciback"
  • Last thing, don’t forget to regenerate your initramfs (this too I dunno how to do on Qubes/Fedora).
  • To correctly adapt the paths to Qubes, read the “credit link” below. In short, in Debian, initramfs scripts in /usr take precedence over initramfs scripts in /etc.

3. End credits ^^

Voilà, I hope it works for you !
For more detailed explanations of how and why it works, and the credit for inspiration, check this link.