Re: [Intel-gfx] [PATCH] drm/i915: Discard a misplaced GGTT vma

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

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

> Across the many users of the GGTT vma (internal objects, mmapings,
> display etc), we may end up with conflicting requirements for the
> placement. Currently, we try to resolve the conflict by unbinding the
> vma and rebinding it to match the new constraints; over time we will end
> up with a GGTT that matches the most strict constraints over all
> concurrent users. However, this causes a problem if the vma is currently
> in use as we must wait until it is idle before moving it. But there is
> no restriction on the number of views we may (apart from the limited

we may...have/impose?
-Mika

> size of the GGTT itself), and so if the active vma does not meet our
> requirements, try and build a new one!
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/i915_gem.c | 44 +++++++++++++++++++++++++++++++++
>  1 file changed, 44 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 0cbcb9f54e7d..29a4594ddef2 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -933,6 +933,44 @@ void i915_gem_runtime_suspend(struct drm_i915_private *i915)
>  	}
>  }
>  
> +static bool
> +discard_ggtt_vma(struct i915_vma *vma, const struct i915_ggtt_view *view)
> +{
> +	const struct i915_ggtt_view discard = {
> +		.type = I915_GGTT_VIEW_PARTIAL,
> +	};
> +	struct drm_i915_gem_object *obj = vma->obj;
> +
> +	spin_lock(&obj->vma.lock);
> +	if (i915_vma_compare(vma, vma->vm, &discard)) {
> +		struct rb_node *rb, **p;
> +
> +		rb_erase(&vma->obj_node, &obj->vma.tree);
> +		vma->ggtt_view = discard;
> +
> +		rb = NULL;
> +		p = &obj->vma.tree.rb_node;
> +		while (*p) {
> +			struct i915_vma *pos;
> +			long cmp;
> +
> +			rb = *p;
> +			pos = rb_entry(rb, struct i915_vma, obj_node);
> +
> +			cmp = i915_vma_compare(pos, vma->vm, &discard);
> +			if (cmp < 0)
> +				p = &rb->rb_right;
> +			else
> +				p = &rb->rb_left;
> +		}
> +		rb_link_node(&vma->obj_node, rb, p);
> +		rb_insert_color(&vma->obj_node, &obj->vma.tree);
> +	}
> +	spin_unlock(&obj->vma.lock);
> +
> +	return i915_vma_compare(vma, vma->vm, view);
> +}
> +
>  struct i915_vma *
>  i915_gem_object_ggtt_pin(struct drm_i915_gem_object *obj,
>  			 const struct i915_ggtt_view *view,
> @@ -979,6 +1017,7 @@ i915_gem_object_ggtt_pin(struct drm_i915_gem_object *obj,
>  			return ERR_PTR(-ENOSPC);
>  	}
>  
> +new_vma:
>  	vma = i915_vma_instance(obj, &ggtt->vm, view);
>  	if (IS_ERR(vma))
>  		return vma;
> @@ -993,6 +1032,11 @@ i915_gem_object_ggtt_pin(struct drm_i915_gem_object *obj,
>  				return ERR_PTR(-ENOSPC);
>  		}
>  
> +		if (i915_vma_is_pinned(vma) || i915_vma_is_active(vma)) {
> +			if (discard_ggtt_vma(vma, view))
> +				goto new_vma;
> +		}
> +
>  		ret = i915_vma_unbind(vma);
>  		if (ret)
>  			return ERR_PTR(ret);
> -- 
> 2.20.1
>
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