From: Venkata Sandeep Dhanalakota <venkata.s.dhanalakota@xxxxxxxxx>
when allocating pages to lmem object of size 4G or greater
we allocate memory blocks from buddy system. In this scenario
buddy sytem can allocate blocks that can have size >= 4G and
these blocks require >32b to represent block size with these
blocks we run into an issue with sg list construction because
sg->length field is only 32b wide.
Hence limit the max allowed block size to less than 4G.
Cc: Niranjana Vishwanathapura <niranjana.vishwanathapura@xxxxxxxxx>
Cc: Matthew Auld <matthew.auld@xxxxxxxxx>
Cc: CQ Tang <cq.tang@xxxxxxxxx>
Signed-off-by: Venkata Sandeep Dhanalakota <venkata.s.dhanalakota@xxxxxxxxx>
---
drivers/gpu/drm/i915/intel_memory_region.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/intel_memory_region.c b/drivers/gpu/drm/i915/intel_memory_region.c
index 6b5e9d88646d..2943c7778d5e 100644
--- a/drivers/gpu/drm/i915/intel_memory_region.c
+++ b/drivers/gpu/drm/i915/intel_memory_region.c
@@ -72,6 +72,7 @@ __intel_memory_region_get_pages_buddy(struct intel_memory_region *mem,
struct list_head *blocks)
{
unsigned int min_order = 0;
+ unsigned int max_order;
unsigned long n_pages;
GEM_BUG_ON(!IS_ALIGNED(size, mem->mm.chunk_size));
@@ -92,13 +93,24 @@ __intel_memory_region_get_pages_buddy(struct intel_memory_region *mem,
n_pages = size >> ilog2(mem->mm.chunk_size);
+ /*
+ * When allocating pages for an lmem object of size > 4G
+ * the memory blocks allocated from buddy system could be
+ * from sizes greater than 4G requiring > 32b to represent
+ * block size. But those blocks cannot be used in sg list
+ * construction(in caller) as sg->length is only 32b wide.
+ * Hence limiting the block size to 4G.
+ */
+ max_order = (ilog2(SZ_4G) - 1) - ilog2(mem->mm.chunk_size);
+
mutex_lock(&mem->mm_lock);
do {
struct i915_buddy_block *block;
unsigned int order;
- order = fls(n_pages) - 1;
+ order = min_t(u32, (fls(n_pages) - 1), max_order);
+
GEM_BUG_ON(order > mem->mm.max_order);
GEM_BUG_ON(order < min_order);
--
2.26.2
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