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

[Joonas Lahtinen <joonas.lahtinen@linux.intel.com>]

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
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