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

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Message-ID: <20260112165914.4086692-43-ben.horgan@arm.com>
Date: Mon, 12 Jan 2026 16:59:09 +0000
From: Ben Horgan <ben.horgan@....com>
To: ben.horgan@....com
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Subject: [PATCH v3 42/47] arm_mpam: resctrl: Add kunit test for mbw min control generation

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@....com>
[horgan: Split test into separate patch]
Signed-off-by: Ben Horgan <ben.horgan@....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