IOMMU for GPUs

Hi

First I have to say I don't know much when it comes to virtual GPUs and
IOMMU. I'm trying to figure out what we have and what is missing in regards
to sharing the GPU to virtual guests on Intel and AMD and things like the
amdkfd driver (for Radeon open compute).

Looking at the state of IOMMU in FreeBSD there seem to be (what I guess is)
a general driver for Intel at /usr/src/sys/x86/iommu/.

Then there's the support for AMD's IOMMU in bhyve at
/usr/src/sys/amd64/vmm/io/iommu.c.

Without looking too much into the details my guess is we have an iommu
driver for Intel that Intel's i915/gvt can use but for AMD there's only the
specific implementation for bhyve and no general driver that other clients
can use... Or?

If anyone wants to work on this, it's up for grabs :)
We'll probably have to add some glue in linuxkpi as well.

Cheers