Quoting Tvrtko Ursulin (2018-06-29 16:08:40)
>
> On 29/06/2018 15:54, Tvrtko Ursulin wrote:
>
> [snip]
>
> >> +int i915_vma_move_to_active(struct i915_vma *vma,
> >> + struct i915_request *rq,
> >> + unsigned int flags)
> >> +{
> >> + struct drm_i915_gem_object *obj = vma->obj;
> >> + struct i915_gem_active *active;
> >> +
> >> + lockdep_assert_held(&rq->i915->drm.struct_mutex);
> >> + GEM_BUG_ON(!drm_mm_node_allocated(&vma->node));
> >> +
> >> + active = lookup_active(vma, rq->fence.context);
> >
> > Never mind the radix tree, but fence.context is u64 as well. And
> > assigned values are continuously incrementing so once >4G of contexts
> > are created and destroyed aliasing is guaranteed with the kernel
> > context, or any old one.
> >
> > It is probably IGT abuse territory, but a) can we be sure it will not
> > open up some exploit, and b) can we swallow this problem ourselves?
>
> Hm.. key the radix tree with the timeline pointer instead? 1:1 to
> fence.context, natural long, and automatic lifetime management.
Lets see.
-Chris
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