Hello all,
I am trying to capture my graphics card at initrd, using vfio, to later pass it through to a virtual machine. Judging by dmesg, the VFIO module does load early, however, the card is not captured at that point and the amdgpu driver is later loaded instead.
This is what I have in my `operating-system` config:
(kernel-arguments '("iommu=pt" "vfio-pci.ids=1002:73bf"))
(initrd-modules (cons* "vfio_pci" "vfio" "vfio_iommu_type1" "vfio_virqfd" %base-initrd-modules))
There are two video cards in the system, both AMD, but different models. The video card of interest is in a separate IOMMU group and the <vendor id>:<device id> combination is correct for my machine.
Best I can tell, vfio-pci.ids argument is not propagated to the module by initramfs. See the following:
Searching online I came up against a GitHub issue for a different initramfs generator that exhibited the same symptoms: VFIO module was loaded, kernel arguments were correct, yet the card was not captured by the vfio driver. The maintainer there did a great job tracking down and fixing the issue and came up with this insight
https://github.com/anatol/booster/issues/20#issuecomment-808956316
After reading kmod code I found that kernel does not use cmdline params
for loadable modules. It was surprising for me. Instead it is expected
that userspace handles cmdline parsing and provides required module
params explicitly.
I tried following the kernel docs to rebind a different driver after boot, but I believe this doesn't work for video cards, and hasn't worked for me.
Any help is greatly appreciated!
Links:
Kernel docs for vfio
Arch guide for GPU passthrough
Thank you!