linux-kernel - [PATCH v4 next 9/9] lib: test_mul_u64_u64_div

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Message-Id: <20251029173828.3682-10-david.laight.linux@gmail.com>
Date: Wed, 29 Oct 2025 17:38:28 +0000
From: David Laight <david.laight.linux@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Cc: David Laight <david.laight.linux@...il.com>,
	u.kleine-koenig@...libre.com,
	Nicolas Pitre <npitre@...libre.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Biju Das <biju.das.jz@...renesas.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Li RongQing <lirongqing@...du.com>,
	Yu Kuai <yukuai3@...wei.com>,
	Khazhismel Kumykov <khazhy@...omium.org>,
	Jens Axboe <axboe@...nel.dk>,
	x86@...nel.org
Subject: [PATCH v4 next 9/9] lib: test_mul_u64_u64_div_u64: Test the 32bit code on 64bit

There are slight differences in the mul_u64_add_u64_div_u64() code
between 32bit and 64bit systems.

Compile and test the 32bit version on 64bit hosts for better test
coverage.

Signed-off-by: David Laight <david.laight.linux@...il.com>
---

Changes for v4:
- Fix build on non x86-64

 lib/math/test_mul_u64_u64_div_u64.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/lib/math/test_mul_u64_u64_div_u64.c b/lib/math/test_mul_u64_u64_div_u64.c
index a3c5e54f37ef..57d5c7158b10 100644
--- a/lib/math/test_mul_u64_u64_div_u64.c
+++ b/lib/math/test_mul_u64_u64_div_u64.c
@@ -74,6 +74,10 @@ done
  */
 
 static u64 test_mul_u64_add_u64_div_u64(u64 a, u64 b, u64 c, u64 d);
+#if __LONG_WIDTH__ >= 64
+#define TEST_32BIT_DIV
+static u64 test_mul_u64_add_u64_div_u64_32bit(u64 a, u64 b, u64 c, u64 d);
+#endif
 
 static int __init test_run(unsigned int fn_no, const char *fn_name)
 {
@@ -100,6 +104,12 @@ static int __init test_run(unsigned int fn_no, const char *fn_name)
 			result = test_mul_u64_add_u64_div_u64(a, b, 0, d);
 			result_up = test_mul_u64_add_u64_div_u64(a, b, d - 1, d);
 			break;
+#ifdef TEST_32BIT_DIV
+		case 2:
+			result = test_mul_u64_add_u64_div_u64_32bit(a, b, 0, d);
+			result_up = test_mul_u64_add_u64_div_u64_32bit(a, b, d - 1, d);
+			break;
+#endif
 		}
 
 		tests += 2;
@@ -131,6 +141,10 @@ static int __init test_init(void)
 		return -EINVAL;
 	if (test_run(1, "test_mul_u64_u64_div_u64"))
 		return -EINVAL;
+#ifdef TEST_32BIT_DIV
+	if (test_run(2, "test_mul_u64_u64_div_u64_32bit"))
+		return -EINVAL;
+#endif
 	return 0;
 }
 
@@ -152,6 +166,21 @@ static void __exit test_exit(void)
 
 #include "div64.c"
 
+#ifdef TEST_32BIT_DIV
+/* Recompile the generic code for 32bit long */
+#undef test_mul_u64_add_u64_div_u64
+#define test_mul_u64_add_u64_div_u64 test_mul_u64_add_u64_div_u64_32bit
+#undef BITS_PER_ITER
+#define BITS_PER_ITER 16
+
+#define mul_u64_u64_add_u64 mul_u64_u64_add_u64_32bit
+#undef mul_u64_long_add_u64
+#undef add_u64_long
+#undef mul_add
+
+#include "div64.c"
+#endif
+
 module_init(test_init);
 module_exit(test_exit);
 
-- 
2.39.5