linux-kernel - [RFC PATCH 22/38] arm_mpam: resctrl: Add kunit test for ABMC/CDP interactions

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Message-Id: <20251205215901.17772-23-james.morse@arm.com>
Date: Fri,  5 Dec 2025 21:58:45 +0000
From: James Morse <james.morse@....com>
To: linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Cc: James Morse <james.morse@....com>,
	D Scott Phillips OS <scott@...amperecomputing.com>,
	carl@...amperecomputing.com,
	lcherian@...vell.com,
	bobo.shaobowang@...wei.com,
	tan.shaopeng@...itsu.com,
	baolin.wang@...ux.alibaba.com,
	Jamie Iles <quic_jiles@...cinc.com>,
	Xin Hao <xhao@...ux.alibaba.com>,
	peternewman@...gle.com,
	dfustini@...libre.com,
	amitsinght@...vell.com,
	David Hildenbrand <david@...nel.org>,
	Dave Martin <dave.martin@....com>,
	Koba Ko <kobak@...dia.com>,
	Shanker Donthineni <sdonthineni@...dia.com>,
	fenghuay@...dia.com,
	baisheng.gao@...soc.com,
	Jonathan Cameron <jonathan.cameron@...wei.com>,
	Gavin Shan <gshan@...hat.com>,
	Ben Horgan <ben.horgan@....com>,
	rohit.mathew@....com,
	reinette.chatre@...el.com,
	Punit Agrawal <punit.agrawal@....qualcomm.com>
Subject: [RFC PATCH 22/38] arm_mpam: resctrl: Add kunit test for ABMC/CDP interactions

ABMC exposes a fun corner case where a platform with one monitor can
use ABMC for assignable counters - but not when CDP is enabled.

Add some tests.

Signed-off-by: James Morse <james.morse@....com>
---
 drivers/resctrl/test_mpam_resctrl.c | 62 +++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)

diff --git a/drivers/resctrl/test_mpam_resctrl.c b/drivers/resctrl/test_mpam_resctrl.c
index d0615aa7671c..c83d54f21fa0 100644
--- a/drivers/resctrl/test_mpam_resctrl.c
+++ b/drivers/resctrl/test_mpam_resctrl.c
@@ -293,6 +293,67 @@ static void test_percent_to_max_rounding(struct kunit *test)
 	KUNIT_EXPECT_LE(test, 4 * num_rounded_up, 3 * total);
 }
 
+static void test_num_assignable_counters(struct kunit *test)
+{
+	unsigned int orig_l3_num_allocated_mbwu = l3_num_allocated_mbwu;
+	u32 orig_mpam_partid_max = mpam_partid_max;
+	u32 orig_mpam_pmg_max = mpam_pmg_max;
+	bool orig_cdp_enabled = cdp_enabled;
+	struct rdt_resource fake_l3;
+
+	/* Force there to be some PARTID/PMG */
+	mpam_partid_max = 3;
+	mpam_pmg_max = 1;
+
+	cdp_enabled = false;
+
+	/* ABMC off, CDP off */
+	l3_num_allocated_mbwu = resctrl_arch_system_num_rmid_idx();
+	mpam_resctrl_monitor_sync_abmc_vals(&fake_l3);
+	KUNIT_EXPECT_EQ(test, fake_l3.mon.num_mbm_cntrs, resctrl_arch_system_num_rmid_idx());
+	KUNIT_EXPECT_FALSE(test, fake_l3.mon.mbm_cntr_assignable);
+	KUNIT_EXPECT_FALSE(test, fake_l3.mon.mbm_assign_on_mkdir);
+
+	/* ABMC on, CDP off */
+	l3_num_allocated_mbwu = 4;
+	mpam_resctrl_monitor_sync_abmc_vals(&fake_l3);
+	KUNIT_EXPECT_EQ(test, fake_l3.mon.num_mbm_cntrs, 4);
+	KUNIT_EXPECT_TRUE(test, fake_l3.mon.mbm_cntr_assignable);
+	KUNIT_EXPECT_TRUE(test, fake_l3.mon.mbm_assign_on_mkdir);
+
+	cdp_enabled = true;
+
+	/* ABMC off, CDP on */
+	l3_num_allocated_mbwu = resctrl_arch_system_num_rmid_idx();
+	mpam_resctrl_monitor_sync_abmc_vals(&fake_l3);
+
+	/* (value not consumed by resctrl) */
+	KUNIT_EXPECT_EQ(test, fake_l3.mon.num_mbm_cntrs, resctrl_arch_system_num_rmid_idx() / 2);
+
+	KUNIT_EXPECT_FALSE(test, fake_l3.mon.mbm_cntr_assignable);
+	KUNIT_EXPECT_FALSE(test, fake_l3.mon.mbm_assign_on_mkdir);
+
+	/* ABMC on, CDP on */
+	l3_num_allocated_mbwu = 4;
+	mpam_resctrl_monitor_sync_abmc_vals(&fake_l3);
+	KUNIT_EXPECT_EQ(test, fake_l3.mon.num_mbm_cntrs, 2);
+	KUNIT_EXPECT_TRUE(test, fake_l3.mon.mbm_cntr_assignable);
+	KUNIT_EXPECT_TRUE(test, fake_l3.mon.mbm_assign_on_mkdir);
+
+	/* ABMC 'on', CDP on - but not enough counters */
+	l3_num_allocated_mbwu = 1;
+	mpam_resctrl_monitor_sync_abmc_vals(&fake_l3);
+	KUNIT_EXPECT_EQ(test, fake_l3.mon.num_mbm_cntrs, 0);
+	KUNIT_EXPECT_FALSE(test, fake_l3.mon.mbm_cntr_assignable);
+	KUNIT_EXPECT_FALSE(test, fake_l3.mon.mbm_assign_on_mkdir);
+
+	/* Restore global variables that were messed with */
+	l3_num_allocated_mbwu = orig_l3_num_allocated_mbwu;
+	mpam_partid_max = orig_mpam_partid_max;
+	mpam_pmg_max = orig_mpam_pmg_max;
+	cdp_enabled = orig_cdp_enabled;
+}
+
 static struct kunit_case mpam_resctrl_test_cases[] = {
 	KUNIT_CASE(test_get_mba_granularity),
 	KUNIT_CASE_PARAM(test_mbw_max_to_percent, test_percent_value_gen_params),
@@ -301,6 +362,7 @@ static struct kunit_case mpam_resctrl_test_cases[] = {
 	KUNIT_CASE(test_percent_to_max_rounding),
 	KUNIT_CASE_PARAM(test_percent_max_roundtrip_stability,
 			 test_all_bwa_wd_gen_params),
+	KUNIT_CASE(test_num_assignable_counters),
 	{}
 };
 
-- 
2.39.5