Re: [PATCH 10/10] iommufd: Allow iommufd to supply /dev/vfio/vfio

[Alex Williamson <alex.williamson@redhat.com>]

On Fri, 28 Oct 2022 15:44:36 -0300
Jason Gunthorpe <jgg@nvidia.com> wrote:

> On Wed, Oct 26, 2022 at 03:31:33PM -0600, Alex Williamson wrote:
> > On Tue, 25 Oct 2022 15:50:45 -0300
> > Jason Gunthorpe <jgg@nvidia.com> wrote:
> >   
> > > If the VFIO container is compiled out, give a kconfig option for iommufd
> > > to provide the miscdev node with the same name and permissions as vfio
> > > uses.
> > > 
> > > The compatibility node supports the same ioctls as VFIO and automatically
> > > enables the VFIO compatible pinned page accounting mode.  
> > 
> > I think I'd like to see some sort of breadcrumb when /dev/vfio/vfio is
> > provided by something other than the vfio container code.  If we intend
> > to include this before P2P is resolved, that breadcrumb   
> 
> I don't belive I can get P2P done soon enough. I plan to do it after
> this is merged. Right now these two series are taking all my time.
> 
> > (dmesg I'm guessing) might also list any known limitations of the
> > compatibility to save time with debugging.  Thanks,  
> 
> Yes, that makes sense.
> 
> Do you want a dmesg at module load time, on every open, or a sysfs
> something? What seems like it would make it into a bug report?

I think dmesg at module load time should probably be ok, every open
seems like harassment and sysfs would require updated support in
various bug reporting tools.  Users are often terrible about reporting
full dmesg in bugs, but they do often filter it for "IOMMU" or "VFIO",
so keep that in mind when crafting the log message.  Thanks,

Alex