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

Joonas Lahtinen
2016-04-18T10:56:15Z

On pe, 2016-04-15 at 11:38 +0100, Chris Wilson wrote:
> 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);

We have:

static inline struct i915_hw_ppgtt *
i915_vm_to_ppgtt(struct i915_address_space *vm)

So rather make a function just like it.

>         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
>
--
Joonas Lahtinen
Open Source Technology Center
Intel Corporation