Re: [PATCH] drm/i915: Use the new vm [un]bind functions

[Ben Widawsky <ben@bwidawsk.net>]

On Fri, Sep 20, 2013 at 11:43:48AM +0100, Chris Wilson wrote:
> On Thu, Sep 19, 2013 at 09:06:39PM -0700, Ben Widawsky wrote:
> > @@ -1117,8 +1114,25 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
> >  	 * batch" bit. Hence we need to pin secure batches into the global gtt.
> >  	 * hsw should have this fixed, but let's be paranoid and do it
> >  	 * unconditionally for now. */
> > -	if (flags & I915_DISPATCH_SECURE && !batch_obj->has_global_gtt_mapping)
> > -		i915_gem_gtt_bind_object(batch_obj, batch_obj->cache_level);
> > +	if (flags & I915_DISPATCH_SECURE) {
> > +		struct i915_address_space *ggtt = obj_to_ggtt(batch_obj);
> > +		/* Assuming all privileged batches are in the global GTT means
> > +		 * we need to make sure we have a global gtt offset, as well as
> > +		 * the PTEs mapped. As mentioned above, we can forego this on
> > +		 * HSW, but don't.
> > +		 */
> > +		ret = i915_gem_object_bind_to_vm(batch_obj, ggtt, 0, false,
> > +						 false);
> > +		if (ret)
> > +			goto err;
> 
> bind_to_vm() has unwanted side-effects here - notably always allocating
> a node and corrupting lists.
> 
> Just pin, ggtt->bind_vma, unpin. Hmmm, except that we also need a
> move_to_active (as we are not presuming vm == ggtt).
> 
> pin, ggtt->bind_vma, move_to_active(ggtt), unpin.
> 
> And then hope we have the correct flushes in place for that to be
> retired if nothing else is going on with that ggtt.

Yes, you're right, and a particular nice catch on the move to active; I
completely forgot. I think ggtt->bind_vma is redundant though. Shouldn't
it just be:
pin, move_to_active, unpin?

Furthermore, the actually pinning (pin count increment) should be
unnecessary, but I assume you were just trying to save me some typing.

> 
> > +
> > +		ggtt->bind_vma(i915_gem_obj_to_ggtt(batch_obj),
> > +			       batch_obj->cache_level,
> > +			       GLOBAL_BIND);
> > +
> > +		exec_start += i915_gem_obj_ggtt_offset(batch_obj);
> > +	} else
> > +		exec_start += i915_gem_obj_offset(batch_obj, vm);
> >  
> >  	ret = i915_gem_execbuffer_move_to_gpu(ring, &eb->vmas);
> >  	if (ret)
> 
> -- 
> Chris Wilson, Intel Open Source Technology Centre

-- 
Ben Widawsky, Intel Open Source Technology Center