[PATCH 3/3] dma-debug: add bucket bound lifetime coverage

[Juanlu Herrero]

Add a KUnit test on a local bucket for conservative bounds, equal-sized
mapping removal, empty-bucket reset and reuse. Exercise the existing
insertion and removal helpers without DMA hardware.

Signed-off-by: Juanlu Herrero <juanlu@xxxxxxxxxxxx>
---
 kernel/dma/Kconfig             | 10 ++++++++
 kernel/dma/debug.c             |  4 +++
 kernel/dma/tests/debug_kunit.c | 57 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 71 insertions(+)

diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
index 3830a63ae032d..3f295a1503597 100644
--- a/kernel/dma/Kconfig
+++ b/kernel/dma/Kconfig
@@ -291,6 +291,16 @@ config DMA_API_DEBUG
 
 	  If unsure, say N.
 
+config DMA_API_DEBUG_KUNIT_TEST
+	bool "Tests for DMA debug bucket bounds" if !KUNIT_ALL_TESTS
+	depends on KUNIT=y && DMA_API_DEBUG
+	default KUNIT_ALL_TESTS
+	help
+	  Enable KUnit (kernel unit test) coverage for DMA debug bucket bounds.
+	  Check that insertion and removal keep the bound conservative and
+	  reset it when a bucket becomes empty. Exercise reuse and equal-sized
+	  mappings on a local bucket. No physical DMA device is required.
+
 config DMA_MAP_BENCHMARK
 	bool "Enable benchmarking of streaming DMA mapping"
 	depends on DEBUG_FS
diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index 8dad45d0a4360..1d0990e447516 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -1700,3 +1700,7 @@ static int __init dma_debug_driver_setup(char *str)
 	return 1;
 }
 __setup("dma_debug_driver=", dma_debug_driver_setup);
+
+#if IS_ENABLED(CONFIG_DMA_API_DEBUG_KUNIT_TEST)
+#include "tests/debug_kunit.c"
+#endif
diff --git a/kernel/dma/tests/debug_kunit.c b/kernel/dma/tests/debug_kunit.c
new file mode 100644
index 0000000000000..96cff02a6918d
--- /dev/null
+++ b/kernel/dma/tests/debug_kunit.c
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <kunit/test.h>
+#include <linux/sizes.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+
+static void dma_debug_bound_lifetime_test(struct kunit *test)
+{
+	struct dma_debug_entry *entries;
+	struct hash_bucket bucket = {};
+	unsigned long bounds[7];
+
+	entries = kunit_kcalloc(test, 3, sizeof(*entries), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, entries);
+	entries[0].size = SZ_4K;
+	entries[1].size = SZ_64K;
+	entries[2].size = SZ_64K;
+	INIT_LIST_HEAD(&bucket.list);
+	spin_lock_init(&bucket.lock);
+	spin_lock(&bucket.lock);
+	hash_bucket_add(&bucket, &entries[0]);
+	bounds[0] = bucket.max_entry_size;
+	hash_bucket_add(&bucket, &entries[1]);
+	hash_bucket_add(&bucket, &entries[2]);
+	bounds[1] = bucket.max_entry_size;
+	hash_bucket_del(&bucket, &entries[1]);
+	bounds[2] = bucket.max_entry_size;
+	hash_bucket_del(&bucket, &entries[2]);
+	bounds[3] = bucket.max_entry_size;
+	hash_bucket_del(&bucket, &entries[0]);
+	bounds[4] = bucket.max_entry_size;
+	hash_bucket_add(&bucket, &entries[0]);
+	bounds[5] = bucket.max_entry_size;
+	hash_bucket_del(&bucket, &entries[0]);
+	bounds[6] = bucket.max_entry_size;
+	spin_unlock(&bucket.lock);
+
+	KUNIT_EXPECT_GE(test, bounds[0], (unsigned long)SZ_4K);
+	KUNIT_EXPECT_GE(test, bounds[1], (unsigned long)SZ_64K);
+	KUNIT_EXPECT_GE(test, bounds[2], (unsigned long)SZ_64K);
+	KUNIT_EXPECT_GE(test, bounds[3], (unsigned long)SZ_4K);
+	KUNIT_EXPECT_EQ(test, bounds[4], 0UL);
+	KUNIT_EXPECT_GE(test, bounds[5], (unsigned long)SZ_4K);
+	KUNIT_EXPECT_EQ(test, bounds[6], 0UL);
+}
+
+static struct kunit_case dma_debug_bound_cases[] = {
+	KUNIT_CASE(dma_debug_bound_lifetime_test),
+	{}
+};
+
+static struct kunit_suite dma_debug_bound_suite = {
+	.name = "dma-debug-bound",
+	.test_cases = dma_debug_bound_cases,
+};
+
+kunit_test_suite(dma_debug_bound_suite);

-- 
2.53.0-Meta