GPU Passthrough of Vega 56 GPU hangs on KVM start.

Submitted by Jam..@..il.com

Assigned to Default DRI bug account

Link to original bug (#110571)

Description

When trying to use IOMMU and passthrough a Vega GPU to the guest VM. KVM fails to start, and SERR errors are shown with lspci on the GPU device.

Hardware is a Threadripper 1950X, Gigabyte X399 Pro motherboard.
Vega 56.

The same problem also happens with an old Radeon CAICOS GPU.

So, my theory is that this is a AMD Threadripper and X399 motherboard problem. Maybe related to the IOMMU programming on the X399 chipset not happening correctly.

Can anyone help give me some pointers as to where to look to help diagnose the problem.
For example, how do I view iommu settings/mappings?
How do I find out what all the config params for the X399 Bridge GPP do?
What does GPP mean?