[vfio-users] amd gpu quirks and command line options

[Allen Dial]

Thank you Alex,


I really appreciate your help!


Allen


On Oct 03, 2018, at 09:42 AM, Alex Williamson <alex.williamson at redhat.com> wrote:


On Wed, 03 Oct 2018 15:13:47 +0000 (GMT)
Allen Dial <adial at mac.com> wrote:

Questions:
1. Is there a known command line, vfio, or grub statemnet that will
allow this passed through gpu to work after guest shutdown or resart
without requireing a state change of the host?

None that I'm aware of.


2. Are vfio or qemu "quirks" items that can help in situations like
these and are "quirks" configurable or initializable somehow?

There are numerous quirks in vfio and QEMU, and I encourage vendors to
add more, but they're generally made to work automatically for the
devices where they apply. We have some quirks for the older Bonaire
and Hawaii AMD GPUs, but nothing for the more recent ones. IIRC there
were some patches in the amdgpu driver to help reset the card, but that
probably only helps for a Linux guest, or perhaps if you bind the device
back to the amdgpu driver in the host.


3. Is there a place where I can go to reference all of the vfio
related kernel options and or paramaters that can be set and is there
a description of each of the possible options/parameters and how to
use them?

You can run modinfo on the vfio kernel options, there's not a lot there
though. In QEMU you can see the device options via '-device
vfio-pci,?'. In both cases, most of the options are for debugging, but
ask for anything you're not sure of. QEMU doesn't provide a way to
describe the options. In general, AMD folks tend to deny that there
are reset issues, so except for the Bonaire/Hawaii quirks above where
they admit there's a silicon issue, we haven't gotten much support for
additional quirks. Thanks,

Alex
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