Re: [patch 0/4] gpu/drm, x86, PAT: Add PAT support for io_mapping_* interface

[Ingo Molnar <mingo@elte.hu>]

* Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> wrote:

> io_mapping_create_wc(), io_mapping_free() and associated map/unmap routines
> are relatively new set of APIs for drivers, that change memory type.
> 
> Currently, these interfaces hardcode WC type on x86 and does not go through
> "PAT enforcement". This patchset adds PAT support for this interface.
> 
> Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
> Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>

hm, the patches look sane and clean and mostly factor out 
existing code and checks and apply them to the io_mapping_*() 
interfaces - so it's something worth having for .29.

But it's all rather awfully late in the cycle and ioremap type 
of bugs typically have 1-2 rc's of latency to be fully 
discovered.

They will probably fix a few regressions and are easy to revert, 
plus they affect the one driver whose authors wrote these 
facilities:

  drivers/gpu/drm/i915/i915_dma.c
  drivers/gpu/drm/i915/i915_gem.c

so maybe we should try it as it's all a clear step forward. I'll 
give them a spin in tip:x86/urgent. Dunno.

Linus, do you have any preference?

	Ingo