[PATCH v3 42/47] arm_mpam: resctrl: Add kunit test for mbw min control generation

Ben Horgan
2026-01-12T17:03:42Z

By default we generate a minimum bandwidth value that is 5% lower
than the maximum bandwidth value given by resctrl.

Add a test for this.

Signed-off-by: James Morse <james.morse@arm.com>
[horgan: Split test into separate patch]
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
drivers/resctrl/test_mpam_devices.c | 66 +++++++++++++++++++++++++++++
1 file changed, 66 insertions(+)

diff --git a/drivers/resctrl/test_mpam_devices.c b/drivers/resctrl/test_mpam_devices.c
index 3e8d564a0c64..2f802fd9f249 100644
--- a/drivers/resctrl/test_mpam_devices.c
+++ b/drivers/resctrl/test_mpam_devices.c
@@ -322,6 +322,71 @@ static void test_mpam_enable_merge_features(struct kunit *test)
mutex_unlock(&mpam_list_lock);
}

+static void test_mpam_extend_config(struct kunit *test)
+{
+ struct mpam_config fake_cfg = { };
+ struct mpam_class fake_class = { };
+
+ /* Configurations with both are not modified */
+ fake_class.props.bwa_wd = 16;
+ fake_cfg.mbw_max = 0xfeef;
+ fake_cfg.mbw_min = 0xfeef;
+ bitmap_zero(fake_cfg.features, MPAM_FEATURE_LAST);
+ mpam_set_feature(mpam_feat_mbw_max, &fake_cfg);
+ mpam_set_feature(mpam_feat_mbw_min, &fake_cfg);
+ mpam_extend_config(&fake_class, &fake_cfg);
+ KUNIT_EXPECT_TRUE(test, mpam_has_feature(mpam_feat_mbw_max, &fake_cfg));
+ KUNIT_EXPECT_TRUE(test, mpam_has_feature(mpam_feat_mbw_min, &fake_cfg));
+ KUNIT_EXPECT_EQ(test, fake_cfg.mbw_max, 0xfeef);
+ KUNIT_EXPECT_EQ(test, fake_cfg.mbw_min, 0xfeef);
+
+ /* When a min is missing, it is generated */
+ fake_class.props.bwa_wd = 16;
+ fake_cfg.mbw_max = 0xfeef;
+ fake_cfg.mbw_min = 0;
+ bitmap_zero(fake_cfg.features, MPAM_FEATURE_LAST);
+ mpam_set_feature(mpam_feat_mbw_max, &fake_cfg);
+ mpam_extend_config(&fake_class, &fake_cfg);
+ KUNIT_EXPECT_TRUE(test, mpam_has_feature(mpam_feat_mbw_max, &fake_cfg));
+ KUNIT_EXPECT_TRUE(test, mpam_has_feature(mpam_feat_mbw_min, &fake_cfg));
+ KUNIT_EXPECT_EQ(test, fake_cfg.mbw_max, 0xfeef);
+ KUNIT_EXPECT_EQ(test, fake_cfg.mbw_min, 0xf224);
+
+ fake_class.props.bwa_wd = 8;
+ fake_cfg.mbw_max = 0xfeef;
+ fake_cfg.mbw_min = 0;
+ bitmap_zero(fake_cfg.features, MPAM_FEATURE_LAST);
+ mpam_set_feature(mpam_feat_mbw_max, &fake_cfg);
+ mpam_extend_config(&fake_class, &fake_cfg);
+ KUNIT_EXPECT_TRUE(test, mpam_has_feature(mpam_feat_mbw_max, &fake_cfg));
+ KUNIT_EXPECT_TRUE(test, mpam_has_feature(mpam_feat_mbw_min, &fake_cfg));
+ KUNIT_EXPECT_EQ(test, fake_cfg.mbw_max, 0xfeef);
+ KUNIT_EXPECT_EQ(test, fake_cfg.mbw_min, 0xf224);
+
+ /* 5% below the minimum granule, is still the minimum granule */
+ fake_class.props.bwa_wd = 12;
+ fake_cfg.mbw_max = 0xf;
+ fake_cfg.mbw_min = 0;
+ bitmap_zero(fake_cfg.features, MPAM_FEATURE_LAST);
+ mpam_set_feature(mpam_feat_mbw_max, &fake_cfg);
+ mpam_extend_config(&fake_class, &fake_cfg);
+ KUNIT_EXPECT_TRUE(test, mpam_has_feature(mpam_feat_mbw_max, &fake_cfg));
+ KUNIT_EXPECT_TRUE(test, mpam_has_feature(mpam_feat_mbw_min, &fake_cfg));
+ KUNIT_EXPECT_EQ(test, fake_cfg.mbw_max, 0xf);
+ KUNIT_EXPECT_EQ(test, fake_cfg.mbw_min, 0xf);
+
+ fake_class.props.bwa_wd = 16;
+ fake_cfg.mbw_max = 0x4;
+ fake_cfg.mbw_min = 0;
+ bitmap_zero(fake_cfg.features, MPAM_FEATURE_LAST);
+ mpam_set_feature(mpam_feat_mbw_max, &fake_cfg);
+ mpam_extend_config(&fake_class, &fake_cfg);
+ KUNIT_EXPECT_TRUE(test, mpam_has_feature(mpam_feat_mbw_max, &fake_cfg));
+ KUNIT_EXPECT_TRUE(test, mpam_has_feature(mpam_feat_mbw_min, &fake_cfg));
+ KUNIT_EXPECT_EQ(test, fake_cfg.mbw_max, 0x4);
+ KUNIT_EXPECT_EQ(test, fake_cfg.mbw_min, 0x0);
+}
+
static void test_mpam_reset_msc_bitmap(struct kunit *test)
{
char __iomem *buf = kunit_kzalloc(test, SZ_16K, GFP_KERNEL);
@@ -378,6 +443,7 @@ static struct kunit_case mpam_devices_test_cases[] = {
KUNIT_CASE(test_mpam_reset_msc_bitmap),
KUNIT_CASE(test_mpam_enable_merge_features),
KUNIT_CASE(test__props_mismatch),
+ KUNIT_CASE(test_mpam_extend_config),
{}
};

--
2.43.0