Taichi x370 USB passthrough

Did anyone get a PCIe USB card passthrough to work on the x370 Taichi?
I have added the acs patch and I’m using downstream,multifunction but still the USB card emerge in one of the big IOMMU groups.

What am I missing?

This board won’t let you pass through a PCIe device unless you put it in the second or third slot.

That’s just how the IOMMU works out.

Are there any x370 boards that can do this now? If so do you know witch?

Also i found this: https://www.reddit.com/r/VFIO/comments/7mirsi/need_help_with_asrock_x370_taichi_with_acs/
It seems he found a way to do it.

Is everything BUT the USB card separated? Here’s my pastebin of my x370 Taichi iommu groups with the ACS patch https://pastebin.com/bAq6emJf

1 Like

My iommu groups looks like in the link in the post above yours. It seems multifunction isn’t triggering correctly for me but i have updated GRUB.

Try dmesg |more and just double check your grub command line is working. There was one time I was trying to figure out what was wrong only to find none of my override/passthrough grub lines were “on”

1 Like

Thanks, I’ll try that when i get home from work.

JFYI - You can update the PCI device ID database with update-pciids (usually located at /usr/sbin/update-pciids). This will give you a bit more detail in the output.


I found the problem, the instructions i was following was putting the “Patch900:acs.patch” line in the wrong place in kernel.spec so it was ignored by the patcher.
One easy hint i found was that dmesg didn’t print “Warning: PCIe ACS overrides enabled…” as shown in the patch code.
Also I found that the 4.15.0 kernel had changes to the drivers/pci/quirks.c file so the patch file didn’t work so i made a new one.

ACS.patch for kernel 4.15.0: https://pastebin.com/8e2sW4GK (use at own risk)
IOMMU groups: https://pastebin.com/pUCuZL1r

It worked great and i’m now passing through the PCIe USB card on the Taichi x370 top x1 slot.

Thanks a lot guys!

1 Like