[Intel-gfx] [PATCH 2/3] drm/i915: Infrastructure for supporting different GGTT views per object

[Chris Wilson]

On Thu, Dec 04, 2014 at 10:19:09AM +0000, Tvrtko Ursulin wrote:
> 
> On 12/04/2014 09:53 AM, Chris Wilson wrote:
> >On Wed, Dec 03, 2014 at 02:59:25PM +0000, Tvrtko Ursulin wrote:
> >>+void i915_vma_bind(struct i915_vma *vma, enum i915_cache_level cache_level,
> >>+		   u32 flags)
> >>+{
> >>+	struct sg_table *pages = i915_ggtt_view_pages(vma);
> >>+
> >>+	if (pages && !IS_ERR(pages)) {
> >>+		vma->bind_vma(vma, pages, cache_level, flags);
> >>+
> >>+		if (vma->ggtt_view.type != I915_GGTT_VIEW_NORMAL) {
> >>+			sg_free_table(pages);
> >>+			kfree(pages);
> >>+		}
> >>+	}
> >>+}
> >
> >Stop. Even if the failure path is impossible with the present
> >implementation, here you are masking the error only to go and pretend
> >the binding succeeded.
> >
> >Don't be lazy, this is a very nasty bug that should be hit during igt -
> >or else you are not testing well enough.
> 
> Fair comment, even if a bit too assuming. I actually had this as
> TODO but somehow lost it.
> 
> I don't have any ideas on how to provoke this to fail from an IGT?
> Even with future implementations it boils down to a couple of small
> allocations which would have to fail reliably.

We have quite a few thrash tests now that are fairly good at getting
even the small allocations to fail.

What we don't have is a single-fd, multi-ctx thrash test (well except
for some GL tests...)
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre