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Date: Wed, 25 Feb 2009 13:08:39 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>,
       Linus Torvalds <torvalds@linux-foundation.org>
Cc: Dave Airlie <airlied@redhat.com>, Jesse Barnes <jbarnes@virtuousgeek.org>,
       Eric Anholt <eric@anholt.net>, Thomas Gleixner <tglx@linutronix.de>,
       H Peter Anvin <hpa@zytor.com>, Keith Packard <keithp@keithp.com>,
       linux-kernel@vger.kernel.org
Subject: Re: [patch 0/4] gpu/drm, x86, PAT: Add PAT support for
	io_mapping_* interface
Message-ID: <20090225120839.GC14279@elte.hu>
References: <20090225013510.010493000@intel.com>
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* 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