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Commit 2d2cfc12 authored by Chris Wilson's avatar Chris Wilson Committed by Jani Nikula
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drm/i915: Recreate internal objects with single page segments if dmar fails 



If we fail to dma-map the object, the most common cause is lack of space
inside the SW-IOTLB due to fragmentation. If we recreate the_sg_table
using segments of PAGE_SIZE (and single page allocations), we may succeed
in remapping the scatterlist.

First became a significant problem for the mock selftests after commit
5584f1b1 ("drm/i915: fix i915 running as dom0 under Xen") increased
the max_order.

Fixes: 920cf419 ("drm/i915: Introduce an internal allocator for disposable private objects")
Fixes: 5584f1b1 ("drm/i915: fix i915 running as dom0 under Xen")
Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170202132721.12711-1-chris@chris-wilson.co.uk


Reviewed-by: default avatarTvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: <stable@vger.kernel.org> # v4.10
(cherry picked from commit bb96dcf5)
Signed-off-by: default avatarJani Nikula <jani.nikula@intel.com>
parent 33b7bfdf

drivers/gpu/drm/i915/i915_gem_internal.c

+23 −14
Original line number Diff line number Diff line
@@ -46,24 +46,12 @@ static struct sg_table * 
i915_gem_object_get_pages_internal(struct drm_i915_gem_object *obj)

{

	struct drm_i915_private *i915 = to_i915(obj->base.dev);

	unsigned int npages = obj->base.size / PAGE_SIZE;

	struct sg_table *st;

	struct scatterlist *sg;

	unsigned int npages;

	int max_order;

	gfp_t gfp;



	st = kmalloc(sizeof(*st), GFP_KERNEL);

	if (!st)

		return ERR_PTR(-ENOMEM);



	if (sg_alloc_table(st, npages, GFP_KERNEL)) {

		kfree(st);

		return ERR_PTR(-ENOMEM);

	}



	sg = st->sgl;

	st->nents = 0;



	max_order = MAX_ORDER;

#ifdef CONFIG_SWIOTLB

	if (swiotlb_nr_tbl()) /* minimum max swiotlb size is IO_TLB_SEGSIZE */
@@ -77,6 +65,20 @@ i915_gem_object_get_pages_internal(struct drm_i915_gem_object *obj) 
		gfp |= __GFP_DMA32;

	}



create_st:

	st = kmalloc(sizeof(*st), GFP_KERNEL);

	if (!st)

		return ERR_PTR(-ENOMEM);



	npages = obj->base.size / PAGE_SIZE;

	if (sg_alloc_table(st, npages, GFP_KERNEL)) {

		kfree(st);

		return ERR_PTR(-ENOMEM);

	}



	sg = st->sgl;

	st->nents = 0;



	do {

		int order = min(fls(npages) - 1, max_order);

		struct page *page;
@@ -104,8 +106,15 @@ i915_gem_object_get_pages_internal(struct drm_i915_gem_object *obj) 
		sg = __sg_next(sg);

	} while (1);



	if (i915_gem_gtt_prepare_pages(obj, st))

	if (i915_gem_gtt_prepare_pages(obj, st)) {

		/* Failed to dma-map try again with single page sg segments */

		if (get_order(st->sgl->length)) {

			internal_free_pages(st);

			max_order = 0;

			goto create_st;

		}

		goto err;

	}



	/* Mark the pages as dontneed whilst they are still pinned. As soon

	 * as they are unpinned they are allowed to be reaped by the shrinker,