Re: [PATCH] drm/i915: Detect invalid scanout pitches

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, Jun 20, 2013 at 01:27:14PM +0100, Chris Wilson wrote:
> On Thu, Jun 20, 2013 at 01:29:10PM +0300, Ville Syrjälä wrote:
> > On Thu, Jun 20, 2013 at 10:14:36AM +0100, Chris Wilson wrote:
> > > On Thu, Jun 20, 2013 at 11:17:16AM +0300, Ville Syrjälä wrote:
> > > > We already have a bit of pitch checking in intel_framebuffer_init().
> > > > In fact there's a FIXME about pre-ilk limits there.
> > > 
> > > It looks tidier to fix that check. We still need to double check the
> > > values though as the tiling mode is independent of the fb config and may
> > > be changed by the user.
> > 
> > True, some checking needs to be done after pinning.
> > 
> > I guess we could have one function that has the checks, and just call it
> > from both places.
> 
> I'm thinking we note the tiling (and anything else of significance)
> during framebuffer_init() and reject the set-base if the object changes.
> I don't think any userspace depends upon being able to change the object
> after AddFB, and I don't think we want to allow the fb/obj to so easily
> become inconsistent.

An alternative idea I've been tossing around is that we'd reject tiling
changes while we have drm_framebuffers pointing at the object. So some
kind of fb_refcount on the object. That would make buggy user space trip
over a bit earlier. But either way seems reasonable to me.

-- 
Ville Syrjälä
Intel OTC