[PATCH] mm/damon/paddr: add KUnit tests for addr_unit conversion

[Aveline Noir <jm5905938@gmail.com>]

damon_pa_phys_addr() and damon_pa_core_addr() convert between DAMON core
addresses and physical addresses using addr_unit.  addr_unit lets 32-bit
kernels with a 64-bit phys_addr_t monitor physical memory above 4 GiB,
but no test covers the conversions.

Add a KUnit suite for both helpers, including a case for addresses above
4 GiB that is skipped when phys_addr_t is 32-bit.

Signed-off-by: Aveline Noir <jm5905938@gmail.com>
---
KUnit passes on x86_64 and i386.  Selftests pass on x86_64, except for
damos_quota.py, which is flaky even without this patch.
---
 mm/damon/Kconfig             | 12 ++++++++++
 mm/damon/paddr.c             |  2 ++
 mm/damon/tests/.kunitconfig  |  4 ++++
 mm/damon/tests/paddr-kunit.h | 55 ++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 73 insertions(+)

diff --git a/mm/damon/Kconfig b/mm/damon/Kconfig
index 34631a44cdec..6f8722fcf464 100644
--- a/mm/damon/Kconfig
+++ b/mm/damon/Kconfig
@@ -65,6 +65,18 @@ config DAMON_VADDR_KUNIT_TEST
 
 	  If unsure, say N.
 
+config DAMON_PADDR_KUNIT_TEST
+	bool "Test for DAMON physical address space operations" if !KUNIT_ALL_TESTS
+	depends on DAMON_PADDR && KUNIT=y
+	default KUNIT_ALL_TESTS
+	help
+	  This builds the DAMON physical address operations Kunit test suite.
+
+	  For more information on KUnit and unit tests in general, please refer
+	  to the KUnit documentation.
+
+	  If unsure, say N.
+
 config DAMON_SYSFS
 	bool "DAMON sysfs interface"
 	depends on DAMON && SYSFS
diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
index 5b773012a876..e89cb14ee17b 100644
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -479,3 +479,5 @@ static int __init damon_pa_initcall(void)
 }
 
 subsys_initcall(damon_pa_initcall);
+
+#include "tests/paddr-kunit.h"
diff --git a/mm/damon/tests/.kunitconfig b/mm/damon/tests/.kunitconfig
index 144d27e6ecc5..9279f0c82be7 100644
--- a/mm/damon/tests/.kunitconfig
+++ b/mm/damon/tests/.kunitconfig
@@ -9,6 +9,10 @@ CONFIG_PAGE_IDLE_FLAG=y
 CONFIG_DAMON_VADDR=y
 CONFIG_DAMON_VADDR_KUNIT_TEST=y
 
+# for DAMON paddr ops
+CONFIG_DAMON_PADDR=y
+CONFIG_DAMON_PADDR_KUNIT_TEST=y
+
 # for DAMON sysfs interface
 CONFIG_SYSFS=y
 CONFIG_DAMON_SYSFS=y
diff --git a/mm/damon/tests/paddr-kunit.h b/mm/damon/tests/paddr-kunit.h
new file mode 100644
index 000000000000..9839cc233071
--- /dev/null
+++ b/mm/damon/tests/paddr-kunit.h
@@ -0,0 +1,55 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Data Access Monitor Unit Tests
+ */
+
+#ifdef CONFIG_DAMON_PADDR_KUNIT_TEST
+
+#ifndef _DAMON_PADDR_TEST_H
+#define _DAMON_PADDR_TEST_H
+
+#include <kunit/test.h>
+
+static void damon_test_pa_phys_addr(struct kunit *test)
+{
+	KUNIT_EXPECT_EQ(test, damon_pa_phys_addr(0x1000, 1), 0x1000);
+	KUNIT_EXPECT_EQ(test, damon_pa_phys_addr(0x40000, 0x1000), 0x40000000);
+}
+
+static void damon_test_pa_core_addr(struct kunit *test)
+{
+	KUNIT_EXPECT_EQ(test, damon_pa_core_addr(0x1000000, 0x1000), 0x1000);
+	/* The conversion rounds down. */
+	KUNIT_EXPECT_EQ(test, damon_pa_core_addr(0x1fff, 0x1000), 1);
+	KUNIT_EXPECT_EQ(test, damon_pa_core_addr(0xfff, 0x1000), 0);
+}
+
+static void damon_test_pa_addr_over_4g(struct kunit *test)
+{
+	unsigned long addr = 0xffffffffUL;
+	unsigned long addr_unit = 0x1000;
+	u64 pa = 0xffffffff000ULL;
+
+	if (!IS_ENABLED(CONFIG_PHYS_ADDR_T_64BIT))
+		kunit_skip(test, "phys_addr_t is 32-bit");
+
+	KUNIT_EXPECT_EQ(test, damon_pa_phys_addr(addr, addr_unit), pa);
+	KUNIT_EXPECT_EQ(test, damon_pa_core_addr(pa, addr_unit), addr);
+}
+
+static struct kunit_case damon_paddr_test_cases[] = {
+	KUNIT_CASE(damon_test_pa_phys_addr),
+	KUNIT_CASE(damon_test_pa_core_addr),
+	KUNIT_CASE(damon_test_pa_addr_over_4g),
+	{},
+};
+
+static struct kunit_suite damon_paddr_test_suite = {
+	.name = "damon-paddr",
+	.test_cases = damon_paddr_test_cases,
+};
+kunit_test_suite(damon_paddr_test_suite);
+
+#endif /* _DAMON_PADDR_TEST_H */
+
+#endif	/* CONFIG_DAMON_PADDR_KUNIT_TEST */

---
base-commit: 2c5dafa7f289d760f4492260b0988029aab478b0
change-id: 20261109-test-damon-paddr-addr-unit-kunit-b2f7e2154de8

Best regards,
--  
Aveline Noir <jm5905938@gmail.com>