Re: [PATCH 1/3] drm/i915: Stop holding a ref to the ppgtt from each vma

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> The context owns both the ppgtt and the vma within it, and our activity
> tracking on the context ensures that we do not release active ppgtt. As
> the context fulfils our obligations for active memory tracking, we can
> relinquish the reference from the vma.
>

The part of owning the vma within it escapes me. The vma is tied
to the object. Is it about that active objects, with their vmas
hold the refs to the context they are executing on?

> This fixes a silly transient refleak from closed vma being kept alive
> until the entire system was idle, keeping all vm alive as well.
>
> Reported-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
> Testcase: igt/gem_ctx_create/files
> Fixes: 3365e2268b6b ("drm/i915: Lazily unbind vma on close")
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_vma.c | 4 ----
>  1 file changed, 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
> index 274fd2a7bcb6..31efc971a3a8 100644
> --- a/drivers/gpu/drm/i915/i915_vma.c
> +++ b/drivers/gpu/drm/i915/i915_vma.c
> @@ -199,7 +199,6 @@ vma_create(struct drm_i915_gem_object *obj,
>  		vma->flags |= I915_VMA_GGTT;
>  		list_add(&vma->obj_link, &obj->vma_list);
>  	} else {
> -		i915_ppgtt_get(i915_vm_to_ppgtt(vm));

It seems this is the sole user of i915_ppgtt_get so you can
remove that too.

-Mika


>  		list_add_tail(&vma->obj_link, &obj->vma_list);
>  	}
>  
> @@ -810,9 +809,6 @@ static void __i915_vma_destroy(struct i915_vma *vma)
>  	if (vma->obj)
>  		rb_erase(&vma->obj_node, &vma->obj->vma_tree);
>  
> -	if (!i915_vma_is_ggtt(vma))
> -		i915_ppgtt_put(i915_vm_to_ppgtt(vma->vm));
> -
>  	rbtree_postorder_for_each_entry_safe(iter, n, &vma->active, node) {
>  		GEM_BUG_ON(i915_gem_active_isset(&iter->base));
>  		kfree(iter);
> -- 
> 2.18.0
>
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