On Thu, Nov 05, 2015 at 05:15:59PM +0530, ankitprasad.r.sharma@xxxxxxxxx wrote:
> From: Ankitprasad Sharma <ankitprasad.r.sharma@xxxxxxxxx>
>
> In pwrite_fast, map an object page by page if obj_ggtt_pin fails. First,
> we try a nonblocking pin for the whole object (since that is fastest if
> reused), then failing that we try to grab one page in the mappable
> aperture. It also allows us to handle objects larger than the mappable
> aperture (e.g. if we need to pwrite with vGPU restricting the aperture
> to a measely 8MiB or something like that).
We already have a fallback to the shmem pwrite. Why do we need this?
-Daniel
>
> Signed-off-by: Ankitprasad Sharma <ankitprasad.r.sharma@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_gem.c | 92 ++++++++++++++++++++++++++++++-----------
> 1 file changed, 69 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index bf5ef7a..9132240 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -766,14 +766,26 @@ i915_gem_gtt_pwrite_fast(struct drm_device *dev,
> struct drm_file *file)
> {
> struct drm_i915_private *dev_priv = dev->dev_private;
> + struct drm_mm_node node;
> ssize_t remain;
> loff_t offset, page_base;
> char __user *user_data;
> - int page_offset, page_length, ret;
> + int page_offset, page_length, ret, i;
> + bool pinned = true;
>
> ret = i915_gem_obj_ggtt_pin(obj, 0, PIN_MAPPABLE | PIN_NONBLOCK);
> - if (ret)
> - goto out;
> + if (ret) {
> + pinned = false;
> + memset(&node, 0, sizeof(node));
> + ret = drm_mm_insert_node_in_range_generic(&dev_priv->gtt.base.mm,
> + &node, 4096, 0,
> + I915_CACHE_NONE, 0,
> + dev_priv->gtt.mappable_end,
> + DRM_MM_SEARCH_DEFAULT,
> + DRM_MM_CREATE_DEFAULT);
> + if (ret)
> + goto out;
> + }
>
> ret = i915_gem_object_set_to_gtt_domain(obj, true);
> if (ret)
> @@ -786,42 +798,76 @@ i915_gem_gtt_pwrite_fast(struct drm_device *dev,
> user_data = to_user_ptr(args->data_ptr);
> remain = args->size;
>
> - offset = i915_gem_obj_ggtt_offset(obj) + args->offset;
> -
> intel_fb_obj_invalidate(obj, ORIGIN_GTT);
>
> - while (remain > 0) {
> - /* Operation in this page
> + if (likely(pinned)) {
> + offset = i915_gem_obj_ggtt_offset(obj) + args->offset;
> + /* Operation in the page
> *
> * page_base = page offset within aperture
> * page_offset = offset within page
> - * page_length = bytes to copy for this page
> + * page_length = bytes to copy for the page
> */
> page_base = offset & PAGE_MASK;
> page_offset = offset_in_page(offset);
> - page_length = remain;
> - if ((page_offset + remain) > PAGE_SIZE)
> - page_length = PAGE_SIZE - page_offset;
> + while (remain > 0) {
> + page_length = remain;
> + if ((page_offset + remain) > PAGE_SIZE)
> + page_length = PAGE_SIZE - page_offset;
> +
> + /* If we get a fault while copying data, then (presumably) our
> + * source page isn't available. Return the error and we'll
> + * retry in the slow path.
> + */
> + if (fast_user_write(dev_priv->gtt.mappable, page_base,
> + page_offset, user_data, page_length)) {
> + ret = -EFAULT;
> + goto out_flush;
> + }
>
> - /* If we get a fault while copying data, then (presumably) our
> - * source page isn't available. Return the error and we'll
> - * retry in the slow path.
> - */
> - if (fast_user_write(dev_priv->gtt.mappable, page_base,
> - page_offset, user_data, page_length)) {
> - ret = -EFAULT;
> - goto out_flush;
> + remain -= page_length;
> + user_data += page_length;
> + page_offset = 0;
> }
> + } else {
> + i = args->offset / PAGE_SIZE;
> + page_offset = offset_in_page(args->offset);
> + while (remain > 0) {
> + page_length = remain;
> + if ((page_offset + remain) > PAGE_SIZE)
> + page_length = PAGE_SIZE - page_offset;
> +
> + wmb();
> + dev_priv->gtt.base.insert_page(&dev_priv->gtt.base,
> + i915_gem_object_get_dma_address(obj, i),
> + node.start,
> + I915_CACHE_NONE,
> + 0);
> + wmb();
> +
> + if (fast_user_write(dev_priv->gtt.mappable, node.start,
> + page_offset, user_data, page_length)) {
> + ret = -EFAULT;
> + goto out_flush;
> + }
>
> - remain -= page_length;
> - user_data += page_length;
> - offset += page_length;
> + remain -= page_length;
> + user_data += page_length;
> + page_offset = 0;
> + i++;
> + }
> + wmb();
> + dev_priv->gtt.base.clear_range(&dev_priv->gtt.base,
> + node.start, node.size,
> + true);
> + drm_mm_remove_node(&node);
> }
>
> out_flush:
> intel_fb_obj_flush(obj, false, ORIGIN_GTT);
> out_unpin:
> - i915_gem_object_ggtt_unpin(obj);
> + if (pinned)
> + i915_gem_object_ggtt_unpin(obj);
> out:
> return ret;
> }
> --
> 1.9.1
>
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--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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