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

[Daniel Vetter <daniel@ffwll.ch>]

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@chromium.org> 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
-- 
Daniel Vetter
Mail: daniel@ffwll.ch
Mobile: +41 (0)79 365 57 48