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

James Morse
2025-10-10T16:53:52Z

Hi Jonathan,

On 12/09/2025 14:37, Jonathan Cameron wrote:
> 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>

Thanks!

>> 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.

Yup, you pointed at the this same shape of bug earlier in the series.

>> 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.

Muscle memory is difficult to overcome ... I've fixed this one, and will keep an eye out
for more.

>> + 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.

Makes sense, Done.

>> +
>> + test_result = (u32 *)(buf + MPAMCFG_CPBM);

Thanks,

James