Re: [PATCH] mm: Work around Intel SNB GTT bug with some physicalpages.

From: Daniel Vetter
Date: Tue May 08 2012 - 13:22:43 EST

On Tue, May 08, 2012 at 08:25:38AM -0700, Linus Torvalds wrote:
> On Mon, May 7, 2012 at 4:13 PM, Stéphane Marchesin <marcheu@xxxxxxxxxxxx> wrote:
> >
> > In the end, I came up with the ugly workaround of just leaking the
> > offending pages in shmem.c.
> Don't leak it.
> Instead, add it to some RCU list, and free it using RCU. Or some
> one-second timer or something.
> That kind of approach should guarantee that it
> (a) gets returned to the system
> but
> (b) the returning to the system gets delayed sufficiently that if the
> i915 driver is doing lots of allocations it will be getting other
> pages.
> Hmm?

The problem is also that this only affects Sandybdrige gpus, so we'd need
to funnel this down to shmfs somehow ... Rob Clarke from Linaro will be
working on a gemfs to make backing storage allocation more flexible - they
need that to support some arm gpus. That way round we wouldn't need to put
some ugly drm/i915 stuff into core shmfs. Rob?
Daniel Vetter
Mail: daniel@xxxxxxxx
Mobile: +41 (0)79 365 57 48
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