Re: [Intel-gfx] [PATCH] intel-gtt: fix memory corruption withGM965 and >4GB RAM

From: Daniel Vetter
Date: Fri Feb 25 2011 - 18:05:55 EST

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@xxxxxxxx
Mobile: +41 (0)79 365 57 48
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