linux-kernel - Re: [Intel-gfx] [PATCH] intel-gtt: fix memory corruption with GM965 and >4GB RAM

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Message-ID: <20110225230527.GC3601@viiv.ffwll.ch>
Date:	Sat, 26 Feb 2011 00:05:27 +0100
From:	Daniel Vetter <daniel@...ll.ch>
To:	Chris Wilson <chris@...is-wilson.co.uk>
Cc:	Jan Niehusmann <jan@...dor.com>, intel-gfx@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: Re: [Intel-gfx] [PATCH] intel-gtt: fix memory corruption with
 GM965 and >4GB RAM

On Fri, Feb 25, 2011 at 10:18:16PM +0000, Chris Wilson wrote:
> So, I'm happy to use your patch to workaround the known erratum. I just
> wish I had an explanation as to what is actually causing the corruption.
> What I want to make sure is that we don't paper over a real bug by
> thinking it is yet another silicon issue.

Actually, on style points I prefer your patch: The hw status page is
allocated with drm_pci_alloc which calls dma_alloc_coherent, so setting
the coherent mask is sufficient. The dma mask set in the gtt is
essentially useless, because we call get_user_pages on everything anyway
(in gem - iirc agp uses it). I just think it's confusing to limit the
general dma mask and continue to happily map pages above 4G.

Cheers, Daniel
-- 
Daniel Vetter
Mail: daniel@...ll.ch
Mobile: +41 (0)79 365 57 48
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