The largest possible order is (63-12), given that our min chunk size is
4K. With that we should only need at most 6 bits to represent all
possible orders, giving us back 4 bits for other potential uses. Include
a simple selftest to verify this.
Signed-off-by: Matthew Auld <matthew.auld@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_buddy.c | 3 ++
drivers/gpu/drm/i915/i915_buddy.h | 7 ++-
drivers/gpu/drm/i915/selftests/i915_buddy.c | 47 +++++++++++++++++++++
3 files changed, 55 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_buddy.c b/drivers/gpu/drm/i915/i915_buddy.c
index 20babbdb297d..650613ae2a7b 100644
--- a/drivers/gpu/drm/i915/i915_buddy.c
+++ b/drivers/gpu/drm/i915/i915_buddy.c
@@ -56,6 +56,9 @@ static struct i915_buddy_block *i915_block_alloc(struct i915_buddy_block *parent
block->header |= order;
block->parent = parent;
+ GEM_BUG_ON(block->header & I915_BUDDY_HEADER_UNUSED);
+ GEM_BUG_ON(order > I915_BUDDY_MAX_ORDER);
+
return block;
}
diff --git a/drivers/gpu/drm/i915/i915_buddy.h b/drivers/gpu/drm/i915/i915_buddy.h
index ed41f3507cdc..d37e03587637 100644
--- a/drivers/gpu/drm/i915/i915_buddy.h
+++ b/drivers/gpu/drm/i915/i915_buddy.h
@@ -15,7 +15,9 @@ struct i915_buddy_block {
#define I915_BUDDY_ALLOCATED (1 << 10)
#define I915_BUDDY_FREE (2 << 10)
#define I915_BUDDY_SPLIT (3 << 10)
-#define I915_BUDDY_HEADER_ORDER GENMASK_ULL(9, 0)
+/* Free to be used, if needed in the future */
+#define I915_BUDDY_HEADER_UNUSED GENMASK_ULL(9, 6)
+#define I915_BUDDY_HEADER_ORDER GENMASK_ULL(5, 0)
u64 header;
struct i915_buddy_block *left;
@@ -34,7 +36,8 @@ struct i915_buddy_block {
struct list_head tmp_link;
};
-#define I915_BUDDY_MAX_ORDER I915_BUDDY_HEADER_ORDER
+/* Order-zero must be at least PAGE_SIZE */
+#define I915_BUDDY_MAX_ORDER (63 - 12)
/*
* Binary Buddy System.
diff --git a/drivers/gpu/drm/i915/selftests/i915_buddy.c b/drivers/gpu/drm/i915/selftests/i915_buddy.c
index 632b912b0bc9..39c470a0e28d 100644
--- a/drivers/gpu/drm/i915/selftests/i915_buddy.c
+++ b/drivers/gpu/drm/i915/selftests/i915_buddy.c
@@ -727,6 +727,52 @@ static int igt_buddy_alloc_range(void *arg)
return err;
}
+static int igt_buddy_alloc_limit(void *arg)
+{
+ struct i915_buddy_block *block;
+ struct i915_buddy_mm mm;
+ const u64 size = U64_MAX;
+ int err;
+
+ err = i915_buddy_init(&mm, size, PAGE_SIZE);
+ if (err)
+ return err;
+
+ if (mm.max_order != I915_BUDDY_MAX_ORDER) {
+ pr_err("mm.max_order(%d) != %d\n",
+ mm.max_order, I915_BUDDY_MAX_ORDER);
+ err = -EINVAL;
+ goto out_fini;
+ }
+
+ block = i915_buddy_alloc(&mm, mm.max_order);
+ if (IS_ERR(block)) {
+ err = PTR_ERR(block);
+ goto out_fini;
+ }
+
+ if (i915_buddy_block_order(block) != I915_BUDDY_MAX_ORDER) {
+ pr_err("block order(%d) != %d\n",
+ i915_buddy_block_order(block), I915_BUDDY_MAX_ORDER);
+ err = -EINVAL;
+ goto out_free;
+ }
+
+ if (i915_buddy_block_size(&mm, block) != rounddown_pow_of_two(size)) {
+ pr_err("block size(%llu) != %lu\n",
+ i915_buddy_block_size(&mm, block),
+ rounddown_pow_of_two(size));
+ err = -EINVAL;
+ goto out_free;
+ }
+
+out_free:
+ i915_buddy_free(&mm, block);
+out_fini:
+ i915_buddy_fini(&mm);
+ return err;
+}
+
int i915_buddy_mock_selftests(void)
{
static const struct i915_subtest tests[] = {
@@ -735,6 +781,7 @@ int i915_buddy_mock_selftests(void)
SUBTEST(igt_buddy_alloc_pathological),
SUBTEST(igt_buddy_alloc_smoke),
SUBTEST(igt_buddy_alloc_range),
+ SUBTEST(igt_buddy_alloc_limit),
};
return i915_subtests(tests, NULL);
--
2.26.2
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