drm/i915/region: fix order when adding blocks

When performing an allocation we try split it down into the largest
possible power-of-two blocks/pages-sizes, and for the common case we
expect to allocate the blocks in descending order. This also naturally
fits with our GTT alignment tricks(including the hugepages selftest),
where we sometimes try to align to the largest possible GTT page-size
for the allocation, in the hope that translates to bigger GTT
page-sizes. Currently, we seem to incorrectly add the blocks in the
opposite order, which is definitely not the intended behaviour.

Reported-by: CQ Tang <cq.tang@intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: CQ Tang <cq.tang@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20201109111249.109365-1-matthew.auld@intel.com

diff --git a/drivers/gpu/drm/i915/intel_memory_region.c b/drivers/gpu/drm/i915/intel_memory_region.c
index 180e1078ef7c1a16421fd118c5e3a54e7e0282eb..b326993a10266750cf6b3752d5658a9eb715ebf8 100644 (file)
--- a/drivers/gpu/drm/i915/intel_memory_region.c
+++ b/drivers/gpu/drm/i915/intel_memory_region.c
@@ -114,7 +114,7 @@ __intel_memory_region_get_pages_buddy(struct intel_memory_region *mem,
                n_pages -= BIT(order);
 
                block->private = mem;
-               list_add(&block->link, blocks);
+               list_add_tail(&block->link, blocks);
 
                if (!n_pages)
                        break;