[vfio-users] Question about iommu groups

[Alex Williamson]

[cc +vfio-users]

On Tue, 18 Jun 2019 15:33:36 +0100
James Courtier-Dutton <james.dutton at gmail.com> wrote:

> Hi,
> 
> I could not see anywhere it mentioning ACS in the dmesg logs, so I don't
> think it is using ACS.
> 
> Is there some way to tell from the logs that ACS is involved.

See previous reply.

> I have 2 AMD Threadripper 1950 systems.
> One has a Gigabyte motherboard, and the IOMMU groups are OK and what I
> expect.
> One has an ASUS motherboard, and the IOMMU groups are problematic.
> I have run the same kernel on both, so I am beginning to suspect a BIOS
> problem.
> 
> Note also, your "vfio-pci-hot-reset.c"  test program works on the Gigabyte,
> but not the ASUS.
> The kernel used in 5.1.5 from mainline, so no ACS patch applied.
> It has my vfio slots patch applied, but nothing else.
> The IOMMU problem also happens with mainline kernel 5.1.11 with no patches
> applied.

You need a version of the hot reset unit test that accepts multiple
devices since each is in a separate group.  The grouping on the Asus
system you provided is preferred, it's not a problem.  Thanks,

Alex