linux-kernel - Re: [PATCH] drm: i915: ensure objects are allocated below 4GB on PAE

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Message-Id: <1243373730.8400.26.camel@gaiman.anholt.net>
Date:	Tue, 26 May 2009 14:35:30 -0700
From:	Eric Anholt <eric@...olt.net>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Kyle McMartin <kyle@...artin.ca>, airlied@...hat.com,
	dri-devel@...ts.sf.net, linux-kernel@...r.kernel.org,
	jbarnes@...tuousgeek.org, stable@...nel.org,
	hugh.dickins@...cali.co.uk, linux-mm@...ck.org,
	shaohua.li@...el.com
Subject: Re: [PATCH] drm: i915: ensure objects are allocated below 4GB on
 PAE

On Tue, 2009-05-26 at 21:17 +0200, Peter Zijlstra wrote:
> On Tue, 2009-05-26 at 12:27 -0400, Kyle McMartin wrote:
> > From: Kyle McMartin <kyle@...hat.com>
> > 
> > Ensure we allocate GEM objects below 4GB on PAE machines, otherwise
> > misery ensues. This patch is based on a patch found on dri-devel by
> > Shaohua Li, but Keith P. expressed reticence that the changes unfairly
> > penalized other hardware.
> > 
> > (The mm/shmem.c hunk is necessary to ensure the DMA32 flag isn't used
> >  by the slab allocator via radix_tree_preload, which will hit a
> >  WARN_ON.)
> 
> Why is this, is the gart not PAE friendly?
> 
> Seems to me its a grand way of promoting 64bit hard/soft-ware.

No, the GART's fine.  But the APIs required to make the AGP code
PAE-friendly got deprecated, so the patches to fix the AGP code got
NAKed, and Venkatesh  never sent out his patches to undeprecate the APIs
and use them.

It's been like 6 months now, and it's absurd.  I'd like to see this
patch go in so people's graphics can start working again and stop
corrupting system memory.

-- 
Eric Anholt
eric@...olt.net                         eric.anholt@...el.com



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