Re: [PATCH v2 28/29] arm_mpam: Add kunit test for bitmap reset

Jonathan Cameron
2025-09-12T13:37:10Z

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);
> +}