From: Arunpravin Paneer Selvam <[email protected]>
Range-restricted allocations (the visible-VRAM aperture) skip
dirty_steer_window() and reach __alloc_range_bias() with no
clear/dirty
eligibility guard, so a dirty allocation freely splits clear
extents (and
vice versa), interleaving the two classes until no large same-class
run
survives and a 4K scanout pin fails with -ENOSPC. Use a two-pass range
search instead: block_incompatible() rejects opposite-class blocks
in the
strict pass and relaxes only when the strict pass returns -ENOSPC,
so a
request still succeeds when only opposite-class space remains. A KUnit
regression test covers the interleaving pattern and fails without the
guard.
Fixes: 1ad5e807f716 ("gpu/buddy: replace dual-tree/force_merge with
decoupled dirty tracker")
Assisted-by: LLM
Cc: Matthew Auld <[email protected]>
Cc: Christian König <[email protected]>
Signed-off-by: Arunpravin Paneer Selvam
<[email protected]>
---
drivers/gpu/buddy.c | 71
++++++++++++++----------------
drivers/gpu/tests/gpu_buddy_test.c | 65 +++++++++++++++++++++++++++
2 files changed, 99 insertions(+), 37 deletions(-)
diff --git a/drivers/gpu/buddy.c b/drivers/gpu/buddy.c
index 2f2aaadafe35..6566bad4fef1 100644
--- a/drivers/gpu/buddy.c
+++ b/drivers/gpu/buddy.c
@@ -1240,11 +1240,19 @@ static void __gpu_buddy_undo_splits(struct
gpu_buddy *mm,
}
}
+static bool block_incompatible(struct gpu_buddy_block *block,
unsigned int flags)
+{
+ bool needs_clear = flags & GPU_BUDDY_CLEAR_ALLOCATION;
+
+ return needs_clear != gpu_buddy_block_is_clear(block);
+}
+
static struct gpu_buddy_block *
__alloc_range_bias(struct gpu_buddy *mm,
u64 start, u64 end,
unsigned int order,
- unsigned long flags)
+ unsigned long flags,
+ bool fallback)
{
u64 req_size = mm->chunk_size << order;
struct gpu_buddy_block *block;
@@ -1258,9 +1266,7 @@ __alloc_range_bias(struct gpu_buddy *mm,
* This range-constrained search hands back the
highest/right-most
* address that satisfies the request: the roots are seeded
high-to-low
* and the right (higher-address) child is descended first,
making
- * top-down the default placement here. A non-top-down clear
request is
- * the only exception, where the descent is biased towards
clear or
- * clear-containing subtrees to satisfy the clear preference.
+ * top-down the default placement here.
*/
for (i = mm->n_roots - 1; i >= 0; --i)
list_add_tail(&mm->roots[i]->tmp_link, &dfs);
@@ -1298,6 +1304,9 @@ __alloc_range_bias(struct gpu_buddy *mm,
continue;
}
+ if (!fallback && block_incompatible(block, flags))
+ continue;
+
if (contains(start, end, block_start, block_end) &&
order == gpu_buddy_block_order(block)) {
/*
@@ -1315,38 +1324,8 @@ __alloc_range_bias(struct gpu_buddy *mm,
goto err_undo;
}
- /*
- * Top-down is a strict address-placement policy, so when
it is
- * requested we ignore clear steering and simply descend the
- * right (higher-address) child first. Only a non-top-down
clear
- * request biases the descent towards clear/has_clear
subtrees.
- */
- if ((flags & GPU_BUDDY_CLEAR_ALLOCATION) &&
- !(flags & GPU_BUDDY_TOPDOWN_ALLOCATION)) {
- struct gpu_buddy_block *prefer;
-
- if (gpu_buddy_block_is_clear(block->right))
- prefer = block->right;
- else if (gpu_buddy_block_is_clear(block->left))
- prefer = block->left;
- else if (block->right->has_clear)
- prefer = block->right;
- else if (block->left->has_clear)
- prefer = block->left;
- else
- prefer = block->right;
-
- if (prefer == block->right) {
- list_add(&block->left->tmp_link, &dfs);
- list_add(&block->right->tmp_link, &dfs);
- } else {
- list_add(&block->right->tmp_link, &dfs);
- list_add(&block->left->tmp_link, &dfs);
- }
- } else {
- list_add(&block->left->tmp_link, &dfs);
- list_add(&block->right->tmp_link, &dfs);
- }
+ list_add(&block->left->tmp_link, &dfs);
+ list_add(&block->right->tmp_link, &dfs);
} while (1);
return ERR_PTR(-ENOSPC);
@@ -1361,6 +1340,24 @@ __alloc_range_bias(struct gpu_buddy *mm,
return ERR_PTR(err);
}
+static struct gpu_buddy_block *
+__gpu_buddy_alloc_range_bias(struct gpu_buddy *mm,
+ u64 start, u64 end,
+ unsigned int order,
+ unsigned long flags)
+{
+ struct gpu_buddy_block *block;
+ bool fallback = false;
+
+ block = __alloc_range_bias(mm, start, end, order,
+ flags, fallback);
+ if (IS_ERR(block))
+ return __alloc_range_bias(mm, start, end, order,
+ flags, !fallback);
+
+ return block;
+}
+
/* Return the highest-address free block of at least @order. */
static struct gpu_buddy_block *
get_maxblock(struct gpu_buddy *mm,
@@ -1924,7 +1921,7 @@ __gpu_buddy_alloc_blocks(struct gpu_buddy *mm,
if (flags & GPU_BUDDY_RANGE_ALLOCATION) {
/* Allocate traversing within the range */
- block = __alloc_range_bias(mm, start, end, order, flags);
+ block = __gpu_buddy_alloc_range_bias(mm, start, end,
order, flags);
if (!IS_ERR(block) || !steered)
return block;
diff --git a/drivers/gpu/tests/gpu_buddy_test.c
b/drivers/gpu/tests/ gpu_buddy_test.c
index b75d32ca6ca0..3eaa261571bf 100644
--- a/drivers/gpu/tests/gpu_buddy_test.c
+++ b/drivers/gpu/tests/gpu_buddy_test.c
@@ -1597,6 +1597,70 @@ static int gpu_buddy_suite_init(struct
kunit_suite *suite)
return 0;
}
+static void gpu_test_buddy_alloc_range_clear_guard(struct kunit
*test)
+{
+ const unsigned long chunk = SZ_1M, mm_size = SZ_4M;
+ struct gpu_buddy_block *block;
+ LIST_HEAD(high_clear_a);
+ LIST_HEAD(high_clear_b);
+ LIST_HEAD(low_dirty);
+ struct gpu_buddy mm;
+ LIST_HEAD(barrier);
+ LIST_HEAD(result);
+
+ KUNIT_ASSERT_FALSE_MSG(test, gpu_buddy_init(&mm, mm_size, chunk),
+ "buddy_init failed\n");
+
+ /*
+ * Lay out a 4 MiB aperture as three regions:
+ *
+ * [0, 1M) dirty free
+ * [1M, 2M) allocated (barrier, keeps the two halves un-
mergeable)
+ * [2M, 4M) clear free (one naturally aligned 2 MiB extent)
+ *
+ * A dirty (non-clear) range allocation must take the low
dirty block
+ * and leave the large clear extent intact. Without the guard the
+ * top-down search cuts the higher clear extent instead and
returns a
+ * clear block -- the interleaving that fragments the aperture
and
+ * ultimately fails a large same-class scanout allocation.
+ */
+ KUNIT_ASSERT_FALSE_MSG(test,
+ gpu_buddy_alloc_blocks(&mm, 0, chunk, chunk,
chunk,
+ &low_dirty,
GPU_BUDDY_RANGE_ALLOCATION),
+ "alloc [0, 1M) failed\n");
+ KUNIT_ASSERT_FALSE_MSG(test,
+ gpu_buddy_alloc_blocks(&mm, chunk, 2 * chunk,
chunk, chunk,
+ &barrier, GPU_BUDDY_RANGE_ALLOCATION),
+ "alloc [1M, 2M) failed\n");
+ KUNIT_ASSERT_FALSE_MSG(test,
+ gpu_buddy_alloc_blocks(&mm, 2 * chunk, 3 *
chunk, chunk, chunk,
+ &high_clear_a,
GPU_BUDDY_RANGE_ALLOCATION),
+ "alloc [2M, 3M) failed\n");
+ KUNIT_ASSERT_FALSE_MSG(test,
+ gpu_buddy_alloc_blocks(&mm, 3 * chunk, 4 *
chunk, chunk, chunk,
+ &high_clear_b,
GPU_BUDDY_RANGE_ALLOCATION),
+ "alloc [3M, 4M) failed\n");
+
+ /* [2M, 4M) coalesces into one aligned clear extent; [0, 1M)
stays dirty. */
+ gpu_buddy_free_list(&mm, &low_dirty, 0);
+ gpu_buddy_free_list(&mm, &high_clear_a, GPU_BUDDY_CLEARED);
+ gpu_buddy_free_list(&mm, &high_clear_b, GPU_BUDDY_CLEARED);
+
+ KUNIT_ASSERT_FALSE_MSG(test,
+ gpu_buddy_alloc_blocks(&mm, 0, mm_size, chunk,
chunk,
+ &result, GPU_BUDDY_RANGE_ALLOCATION),
+ "dirty range alloc failed\n");
+
+ block = list_first_entry(&result, struct gpu_buddy_block, link);
+ KUNIT_EXPECT_FALSE_MSG(test, gpu_buddy_block_is_clear(block),
+ "dirty range alloc cut the clear extent
(offset=%llx)\n",
+ gpu_buddy_block_offset(block));
+
+ gpu_buddy_free_list(&mm, &result, 0);
+ gpu_buddy_free_list(&mm, &barrier, 0);
+ gpu_buddy_fini(&mm);
+}
+
static struct kunit_case gpu_buddy_tests[] = {
KUNIT_CASE(gpu_test_buddy_alloc_limit),
KUNIT_CASE(gpu_test_buddy_alloc_optimistic),
@@ -1606,6 +1670,7 @@ static struct kunit_case gpu_buddy_tests[] = {
KUNIT_CASE(gpu_test_buddy_alloc_clear),
KUNIT_CASE(gpu_test_buddy_alloc_range),
KUNIT_CASE(gpu_test_buddy_alloc_range_bias),
+ KUNIT_CASE(gpu_test_buddy_alloc_range_clear_guard),
KUNIT_CASE_SLOW(gpu_test_buddy_fragmentation_performance),
KUNIT_CASE_SLOW(gpu_test_buddy_dirty_tracker_performance),
KUNIT_CASE(gpu_test_buddy_alloc_exceeds_max_order),
base-commit: f146c6086b792cb2c6b3ce5106f0cce62e408df8
