[Intel-gfx] [PATCH] drm/i915: Enforce execobject.alignment to be a power-of-two

[Daniel Vetter]

On Mon, Jun 22, 2015 at 12:03:08PM +0100, Damien Lespiau wrote:
> On Fri, Jun 19, 2015 at 01:59:46PM +0100, Chris Wilson wrote:
> > Internal requirement for the alignment is that it must be a
> > power-of-two, so enforce rejection at the user interface to execbuffer
> > (which allows the caller to specify a stricter-than-expected alignment
> > criterion).
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> 
> That sounds right in general and I could find at least one instance
> where we rely on alignment being a power of two (eb_vma_misplaced() and
> vma->node.start & (entry->alignment - 1))
> 
> so:
> 
> Reviewed-by: Damien Lespiau <damien.lespiau at intel.com>

Needs a nasty igt I think ... Do we have? Applied meanwhile.
-Daniel

> 
> -- 
> Damien
> 
> > ---
> >  drivers/gpu/drm/i915/i915_gem_execbuffer.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> > index f4fb2bd33753..b14733908d8d 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> > +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> > @@ -1189,6 +1189,9 @@ validate_exec_list(const struct drm_i915_gem_execbuffer2 *args,
> >  		if (exec[i].flags & invalid_flags)
> >  			return -EINVAL;
> >  
> > +		if (exec[i].alignment && !is_power_of_2(exec[i].alignment))
> > +			return -EINVAL;
> > +
> >  		/* pad_to_size was once a reserved field, so sanitize it */
> >  		if (exec[i].flags & EXEC_OBJECT_PAD_TO_SIZE) {
> >  			if (offset_in_page(exec[i].pad_to_size))
> > -- 
> > 2.1.4
> > 
> > _______________________________________________
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> > Intel-gfx at lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch