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
5584f1b1d73e ("drm/i915: fix i915 running as dom0 under Xen") increased
the max_order.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem_internal.c | 37 ++++++++++++++++++++------------
1 file changed, 23 insertions(+), 14 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem_internal.c b/drivers/gpu/drm/i915/i915_gem_internal.c
index 2b9d5e94a8ae..fc950abbe400 100644
--- a/drivers/gpu/drm/i915/i915_gem_internal.c
+++ b/drivers/gpu/drm/i915/i915_gem_internal.c
@@ -48,24 +48,12 @@ 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()) {
@@ -87,6 +75,20 @@ 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;
@@ -114,8 +116,15 @@ 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,
--
2.11.0
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