The bitmap reset code has been a source of bugs. Add a unit test.

This currently has to be built in, as the rest of the driver is
builtin.

Suggested-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: James Morse <james.morse@arm.com>
---
 drivers/resctrl/Kconfig             | 10 +++++
 drivers/resctrl/mpam_devices.c      |  4 ++
 drivers/resctrl/test_mpam_devices.c | 68 +++++++++++++++++++++++++++++
 3 files changed, 82 insertions(+)
 create mode 100644 drivers/resctrl/test_mpam_devices.c

diff --git a/drivers/resctrl/Kconfig b/drivers/resctrl/Kconfig
index c30532a3a3a4..ef59b3057d5d 100644
--- a/drivers/resctrl/Kconfig
+++ b/drivers/resctrl/Kconfig
@@ -5,10 +5,20 @@ menuconfig ARM64_MPAM_DRIVER
 	  MPAM driver for System IP, e,g. caches and memory controllers.
 
 if ARM64_MPAM_DRIVER
+
 config ARM64_MPAM_DRIVER_DEBUG
 	bool "Enable debug messages from the MPAM driver"
 	depends on ARM64_MPAM_DRIVER
 	help
 	  Say yes here to enable debug messages from the MPAM driver.
 
+config MPAM_KUNIT_TEST
+	bool "KUnit tests for MPAM driver " if !KUNIT_ALL_TESTS
+	depends on KUNIT=y
+	default KUNIT_ALL_TESTS
+	help
+	  Enable this option to run tests in the MPAM driver.
+
+	  If unsure, say N.
+
 endif
diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index 8254d6190ca2..2962cd018207 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -2662,3 +2662,7 @@ static int __init mpam_msc_driver_init(void)
 }
 /* Must occur after arm64_mpam_register_cpus() from arch_initcall() */
 subsys_initcall(mpam_msc_driver_init);
+
+#ifdef CONFIG_MPAM_KUNIT_TEST
+#include "test_mpam_devices.c"
+#endif
diff --git a/drivers/resctrl/test_mpam_devices.c b/drivers/resctrl/test_mpam_devices.c
new file mode 100644
index 000000000000..3e7058f7601c
--- /dev/null
+++ b/drivers/resctrl/test_mpam_devices.c
@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2024 Arm Ltd.
+/* This file is intended to be included into mpam_devices.c */
+
+#include <kunit/test.h>
+
+static void test_mpam_reset_msc_bitmap(struct kunit *test)
+{
+	char __iomem *buf = kunit_kzalloc(test, SZ_16K, GFP_KERNEL);
+	struct mpam_msc fake_msc = {0};
+	u32 *test_result;
+
+	if (!buf)
+		return;
+
+	fake_msc.mapped_hwpage = buf;
+	fake_msc.mapped_hwpage_sz = SZ_16K;
+	cpumask_copy(&fake_msc.accessibility, cpu_possible_mask);
+
+	mutex_init(&fake_msc.part_sel_lock);
+	mutex_lock(&fake_msc.part_sel_lock);
+
+	test_result = (u32 *)(buf + MPAMCFG_CPBM);
+
+	mpam_reset_msc_bitmap(&fake_msc, MPAMCFG_CPBM, 0);
+	KUNIT_EXPECT_EQ(test, test_result[0], 0);
+	KUNIT_EXPECT_EQ(test, test_result[1], 0);
+	test_result[0] = 0;
+	test_result[1] = 0;
+
+	mpam_reset_msc_bitmap(&fake_msc, MPAMCFG_CPBM, 1);
+	KUNIT_EXPECT_EQ(test, test_result[0], 1);
+	KUNIT_EXPECT_EQ(test, test_result[1], 0);
+	test_result[0] = 0;
+	test_result[1] = 0;
+
+	mpam_reset_msc_bitmap(&fake_msc, MPAMCFG_CPBM, 16);
+	KUNIT_EXPECT_EQ(test, test_result[0], 0xffff);
+	KUNIT_EXPECT_EQ(test, test_result[1], 0);
+	test_result[0] = 0;
+	test_result[1] = 0;
+
+	mpam_reset_msc_bitmap(&fake_msc, MPAMCFG_CPBM, 32);
+	KUNIT_EXPECT_EQ(test, test_result[0], 0xffffffff);
+	KUNIT_EXPECT_EQ(test, test_result[1], 0);
+	test_result[0] = 0;
+	test_result[1] = 0;
+
+	mpam_reset_msc_bitmap(&fake_msc, MPAMCFG_CPBM, 33);
+	KUNIT_EXPECT_EQ(test, test_result[0], 0xffffffff);
+	KUNIT_EXPECT_EQ(test, test_result[1], 1);
+	test_result[0] = 0;
+	test_result[1] = 0;
+
+	mutex_unlock(&fake_msc.part_sel_lock);
+}
+
+static struct kunit_case mpam_devices_test_cases[] = {
+	KUNIT_CASE(test_mpam_reset_msc_bitmap),
+	{}
+};
+
+static struct kunit_suite mpam_devices_test_suite = {
+	.name = "mpam_devices_test_suite",
+	.test_cases = mpam_devices_test_cases,
+};
+
+kunit_test_suites(&mpam_devices_test_suite);
-- 
2.39.5

On 9/10/25 13:43, James Morse wrote:
> The bitmap reset code has been a source of bugs. Add a unit test.
>
> This currently has to be built in, as the rest of the driver is
> builtin.
>
> Suggested-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Signed-off-by: James Morse <james.morse@arm.com>

Reviewed-by: Fenghua Yu <fenghuay@nvidia.com>

Thanks.

-Fenghua

Hi James,

On 9/10/25 21:43, James Morse wrote:
> The bitmap reset code has been a source of bugs. Add a unit test.
> 
> This currently has to be built in, as the rest of the driver is
> builtin.
> 
> Suggested-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Signed-off-by: James Morse <james.morse@arm.com>
> ---
>  drivers/resctrl/Kconfig             | 10 +++++
>  drivers/resctrl/mpam_devices.c      |  4 ++
>  drivers/resctrl/test_mpam_devices.c | 68 +++++++++++++++++++++++++++++
>  3 files changed, 82 insertions(+)
>  create mode 100644 drivers/resctrl/test_mpam_devices.c
> 
> diff --git a/drivers/resctrl/Kconfig b/drivers/resctrl/Kconfig
> index c30532a3a3a4..ef59b3057d5d 100644
> --- a/drivers/resctrl/Kconfig
> +++ b/drivers/resctrl/Kconfig
> @@ -5,10 +5,20 @@ menuconfig ARM64_MPAM_DRIVER
>  	  MPAM driver for System IP, e,g. caches and memory controllers.
>  
>  if ARM64_MPAM_DRIVER
> +

Nit: add the empty line in an earlier patch

Reviewed-by: Ben Horgan <ben.horgan@arm.com>

Thanks,

Ben

On Wed, 10 Sep 2025 20:43:08 +0000
James Morse <james.morse@arm.com> wrote:

> The bitmap reset code has been a source of bugs. Add a unit test.
> 
> This currently has to be built in, as the rest of the driver is
> builtin.
> 
> Suggested-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Signed-off-by: James Morse <james.morse@arm.com>
Few trivial comments inline.

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

> ---
>  drivers/resctrl/Kconfig             | 10 +++++
>  drivers/resctrl/mpam_devices.c      |  4 ++
>  drivers/resctrl/test_mpam_devices.c | 68 +++++++++++++++++++++++++++++
>  3 files changed, 82 insertions(+)
>  create mode 100644 drivers/resctrl/test_mpam_devices.c
> 
> diff --git a/drivers/resctrl/Kconfig b/drivers/resctrl/Kconfig
> index c30532a3a3a4..ef59b3057d5d 100644
> --- a/drivers/resctrl/Kconfig
> +++ b/drivers/resctrl/Kconfig
> @@ -5,10 +5,20 @@ menuconfig ARM64_MPAM_DRIVER
>  	  MPAM driver for System IP, e,g. caches and memory controllers.
>  
>  if ARM64_MPAM_DRIVER
> +
>  config ARM64_MPAM_DRIVER_DEBUG
>  	bool "Enable debug messages from the MPAM driver"
>  	depends on ARM64_MPAM_DRIVER

Doing this under an if for the same isn't useful. So if you want to do this
style I'd do it before adding this earlier config option.

>  	help
>  	  Say yes here to enable debug messages from the MPAM driver.
>  
> +config MPAM_KUNIT_TEST
> +	bool "KUnit tests for MPAM driver " if !KUNIT_ALL_TESTS
> +	depends on KUNIT=y
> +	default KUNIT_ALL_TESTS
> +	help
> +	  Enable this option to run tests in the MPAM driver.
> +
> +	  If unsure, say N.
> +
>  endif

> diff --git a/drivers/resctrl/test_mpam_devices.c b/drivers/resctrl/test_mpam_devices.c
> new file mode 100644
> index 000000000000..3e7058f7601c
> --- /dev/null
> +++ b/drivers/resctrl/test_mpam_devices.c
> @@ -0,0 +1,68 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (C) 2024 Arm Ltd.
> +/* This file is intended to be included into mpam_devices.c */
> +
> +#include <kunit/test.h>
> +
> +static void test_mpam_reset_msc_bitmap(struct kunit *test)
> +{
> +	char __iomem *buf = kunit_kzalloc(test, SZ_16K, GFP_KERNEL);
> +	struct mpam_msc fake_msc = {0};

= { }; is sufficient and what newer c specs have adopted to mean
fill everything including holes in structures with 0.  There are some
tests that ensure that behavior applies with older compilers + the options
we use for building the kernel.

> +	u32 *test_result;
> +
> +	if (!buf)
> +		return;
> +
> +	fake_msc.mapped_hwpage = buf;
> +	fake_msc.mapped_hwpage_sz = SZ_16K;
> +	cpumask_copy(&fake_msc.accessibility, cpu_possible_mask);
> +
> +	mutex_init(&fake_msc.part_sel_lock);
> +	mutex_lock(&fake_msc.part_sel_lock);

Perhaps add a comment to say this is to satisfy lock markings?
Otherwise someone might wonder why mutex_init() immediately followed
by taking the lock maskes sense.

> +
> +	test_result = (u32 *)(buf + MPAMCFG_CPBM);
> +
> +	mpam_reset_msc_bitmap(&fake_msc, MPAMCFG_CPBM, 0);
> +	KUNIT_EXPECT_EQ(test, test_result[0], 0);
> +	KUNIT_EXPECT_EQ(test, test_result[1], 0);
> +	test_result[0] = 0;
> +	test_result[1] = 0;
> +
> +	mpam_reset_msc_bitmap(&fake_msc, MPAMCFG_CPBM, 1);
> +	KUNIT_EXPECT_EQ(test, test_result[0], 1);
> +	KUNIT_EXPECT_EQ(test, test_result[1], 0);
> +	test_result[0] = 0;
> +	test_result[1] = 0;
> +
> +	mpam_reset_msc_bitmap(&fake_msc, MPAMCFG_CPBM, 16);
> +	KUNIT_EXPECT_EQ(test, test_result[0], 0xffff);
> +	KUNIT_EXPECT_EQ(test, test_result[1], 0);
> +	test_result[0] = 0;
> +	test_result[1] = 0;
> +
> +	mpam_reset_msc_bitmap(&fake_msc, MPAMCFG_CPBM, 32);
> +	KUNIT_EXPECT_EQ(test, test_result[0], 0xffffffff);
> +	KUNIT_EXPECT_EQ(test, test_result[1], 0);
> +	test_result[0] = 0;
> +	test_result[1] = 0;
> +
> +	mpam_reset_msc_bitmap(&fake_msc, MPAMCFG_CPBM, 33);
> +	KUNIT_EXPECT_EQ(test, test_result[0], 0xffffffff);
> +	KUNIT_EXPECT_EQ(test, test_result[1], 1);
> +	test_result[0] = 0;
> +	test_result[1] = 0;
> +
> +	mutex_unlock(&fake_msc.part_sel_lock);
> +}