Re: [PATCH] drm/i915: Move ioremap_wc tracking onto VMA

Chris Wilson
2016-04-15T10:38:12Z

On Fri, Apr 15, 2016 at 11:19:30AM +0100, Tvrtko Ursulin wrote:
> On 15/04/16 11:00, Chris Wilson wrote:
> >On Fri, Apr 15, 2016 at 10:40:42AM +0100, Tvrtko Ursulin wrote:
> >>
> >>On 13/04/16 16:12, Chris Wilson wrote:
> >>>On Wed, Apr 13, 2016 at 03:47:58PM +0100, Chris Wilson wrote:
> >>>>+ /* We also want to clear any cached iomaps as they wrap vmap */
> >>>>+ list_for_each_entry_safe(vma, next,
> >>>>+ &dev_priv->ggtt.base.inactive_list, vm_link)
> >>>>+ if (vma->iomap && i915_vma_unbind(vma) == 0)
> >>>>+ freed_pages += vma->node.size >> PAGE_SHIFT;
> >>>
> >>>Use after free. I need to store the page count in a local before calling
> >>>unbind.
> >>
> >>Waiting for respin. :)
> >>
> >>Also, shouldn't the patch which adds the size argument to
> >>io_mapping_map_wc be in this series?
> >
> >It was, this was just an update to patch 2. The delta here is just
> >unsigned long count = vma->node.size >> PAGE_SHIFT;
> >if (vma->iomap && i915_vma_unbind(vma) == 0)
> > freed_pages += count;
>
> My bad, I got lost in the threads.. :(
>
> Could I ask for those two BUG_ONs to be replaced with GEM_BUG_ONs
> now that is in?
>
> Maybe also add a quick return at the top, as a micro-opt:
>
> if (vma->iomap)
> reutrn vma->iomap;
>
> Followed by WARNs, GEM_BUG_ONs and rest?

Like so?

void *i915_vma_iomap(struct i915_vma *vma)
{
struct i915_ggtt *ggtt;
void *ptr;

if (vma->iomap)
return vma->iomap;

if (WARN_ON(!vma->obj->map_and_fenceable))
return ERR_PTR(-ENODEV);

GEM_BUG_ON(!vma->is_ggtt);
GEM_BUG_ON((vma->bound & GLOBAL_BIND) == 0);

ggtt = container_of(vma->vm, struct i915_ggtt, base);
ptr = io_mapping_map_wc(ggtt->mappable vma->node.start, vma->node.size);
if (ptr == NULL)
return ERR_PTR(-ENOMEM);

vma->iomap = ptr;
return ptr;
}
-Chris

--
Chris Wilson, Intel Open Source Technology Centre