Re: vfio: failed to select IOMMU type

[Alejandro Lucero <alejandro.lucero@netronome.com>]

Hi Andrew, Anatoly,

On Tue, Apr 4, 2017 at 4:52 PM, Burakov, Anatoly <anatoly.burakov@intel.com>
wrote:

> Hi Andrew,
>
> > I think a key to the main problem is the same IOMMU group used for both
> PCI functions.
> > It tries to set IOMMU type using the same file descriptor twice. The
> second set is dummy, since the same value is set, but still fails, I guess,
> because it is already in use.
> > See logs with debug enabled and few extra logs below:
>
> Yes you're right. Specifically, eal_vfio.c:vfio_setup_device() at line
> 311 (where we check for number of groups) - the code always assumes that one
> active group means we've just initialized a new group, which may not
> necessarily be the case if there's more than one device per group.
>
>
Yes, the code was not aware of that possibility. Being honest, I knew about
that, but not in my mind when implementing the code. I have just cards
where each PF even VF have their own VFIO group. This could be a problem
for testing. Anatoly, do you have a system with that peculiarity?


> Alejandro, please correct me if I'm wrong, but I think this raises another
> issue: vfio_release_device() seems to attempt to close group fd
> unconditionally,
> which is probably a bad idea if there are more than one device per group.
>
>
Yes, I think so, but not completely sure. Doing a quick look at kernel VFIO
code, that seems a problem, but need more time for studying the code again.
Again, not having hardware with this peculiarity will make the process
harder.


> Would you be so kind to come up with a patch to fix this oversight, or
> should I do it? :)
>
>
Yes, I will work on this as a priority and send a patch asap. Andrew, could
you test this hotplug option in some way with your systems?

Thanks


> Thanks,
> Anatoly
>