[Intel-gfx] [PATCH 1/3] drm/i915: Support for pre-populating the object with system pages

[Chris Wilson]

On Mon, Aug 24, 2015 at 05:28:14PM +0530, ankitprasad.r.sharma at intel.com wrote:
> +static int
> +__i915_gem_object_get_pages(struct drm_i915_gem_object *obj)
> +{
> +	const struct drm_i915_gem_object_ops *ops = obj->ops;
> +	int ret;
> +
> +	WARN_ON(obj->pages);
> +
> +	if (obj->madv != I915_MADV_WILLNEED) {
> +		DRM_DEBUG("Attempting to obtain a purgeable object\n");
> +		return -EFAULT;
> +	}
> +
> +	BUG_ON(obj->pages_pin_count);

Put the parameter checking into i915_gem_object_get_pages(). The __i915
version is only allowed from strict contexts and we can place the burden
of being correct on the caller.

> +	ret = ops->get_pages(obj);
> +	if (ret)
> +		return ret;
> +
> +	obj->get_page.sg = obj->pages->sgl;
> +	obj->get_page.last = 0;
> +
> +	return 0;
> +}
> +
>  /* Ensure that the associated pages are gathered from the backing storage
>   * and pinned into our object. i915_gem_object_get_pages() may be called
>   * multiple times before they are released by a single call to
> @@ -2339,28 +2377,17 @@ int
>  i915_gem_object_get_pages(struct drm_i915_gem_object *obj)
>  {
>  	struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
> -	const struct drm_i915_gem_object_ops *ops = obj->ops;
>  	int ret;
>  
>  	if (obj->pages)
>  		return 0;
>  
> -	if (obj->madv != I915_MADV_WILLNEED) {
> -		DRM_DEBUG("Attempting to obtain a purgeable object\n");
> -		return -EFAULT;
> -	}
> -
> -	BUG_ON(obj->pages_pin_count);
> -
> -	ret = ops->get_pages(obj);
> +	ret = __i915_gem_object_get_pages(obj);
>  	if (ret)
>  		return ret;
>  
>  	list_add_tail(&obj->global_list, &dev_priv->mm.unbound_list);

I am tempted to say this should be in a new

__i915_gem_object_get_pages__tail_locked()

so that we don't have to hunt down users if we ever need to modify the
global lists.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre