[Intel-gfx] [PATCH] make KMS resource mappings exclusive

[Jesse Barnes]

On Monday, March 9, 2009 3:29:40 am Simon Farnsworth wrote:
> Eric Anholt wrote:
> > On Mon, 2009-01-19 at 13:00 -0800, Jesse Barnes wrote:
> >> This should help avoid problems with unsupported userspace programs or
> >> configurations running on top of a KMS enabled driver.  Updates the
> >> ioremap to nocache as well, since that's really what we want to track.
> >>
> >> Signed-off-by: Jesse Barnes <jbarnes at virtuousgeek.org>
> >
> > For the record: the reason I've avoided doing this one is that when
> > jbarnes and I talked, we figured that this prevents userland from
> > mapping at all, though we really only care about preventing write
> > mapping of the registers/aperture.  Since we've still got a bunch of
> > really useful userland tools for debugging that rely on read-only
> > mapping of registers, we're pending this until we get that information
> > into the kernel somehow.
>
> Is there a reason why booting with iomem=relaxed isn't enough to let the
> userspace tools work?

No, that should work, but it does make things a lot more difficult for 
testers, since it means they'd likely have to reboot to collect dumps, rather 
than just collecting them when they run into a problem.  Eventually we'll be 
able to restrict the mappings though, after we support dumping the relevant 
info from debugfs instead.

-- 
Jesse Barnes, Intel Open Source Technology Center