[Intel-gfx] [PATCH 2/2] drm/i915: Limit the scattergather coalescing to 32bits

[Chris Wilson]

On Fri, Oct 14, 2016 at 04:38:35PM +0100, Tvrtko Ursulin wrote:
> 
> On 14/10/2016 16:18, Chris Wilson wrote:
> >The scattergather list uses a 32bit size counter, we should avoid
> >exceeding it.
> >
> >Fixes: 871dfbd67d4e ("drm/i915: Allow compaction upto SWIOTLB max segment size")
> >Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> >---
> >  drivers/gpu/drm/i915/i915_gem.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> >diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> >index 0d1dc04302ec..858569419134 100644
> >--- a/drivers/gpu/drm/i915/i915_gem.c
> >+++ b/drivers/gpu/drm/i915/i915_gem.c
> >@@ -2238,7 +2238,7 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
> >  	max_segment = swiotlb_max_size();
> >  	if (!max_segment)
> >-		max_segment = obj->base.size;
> >+		max_segment = rounddown(UINT_MAX, PAGE_SIZE);
> >  	st = kmalloc(sizeof(*st), GFP_KERNEL);
> >  	if (st == NULL)
> 
> I suppose it could be possible to get more that 4GiB of of contiguous pages.
> 
> sg_alloc_table_from_pages seems broken as well, for this, and more
> so, for using longs and stuffing them into ints.

Noticed I was using unsigned long max_segment. Any complaints if I
change that to unsigned int as well?
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre