linux-kernel - [RFC PATCH 24/36] arm_mpam: Extend reset logic to allow devices to be reset any time

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Message-Id: <20250711183648.30766-25-james.morse@arm.com>
Date: Fri, 11 Jul 2025 18:36:36 +0000
From: James Morse <james.morse@....com>
To: linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Cc: Rob Herring <robh@...nel.org>,
	Ben Horgan <ben.horgan@....com>,
	Rohit Mathew <rohit.mathew@....com>,
	Shanker Donthineni <sdonthineni@...dia.com>,
	Zeng Heng <zengheng4@...wei.com>,
	Lecopzer Chen <lecopzerc@...dia.com>,
	Carl Worth <carl@...amperecomputing.com>,
	shameerali.kolothum.thodi@...wei.com,
	D Scott Phillips OS <scott@...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@...hat.com>,
	Rex Nie <rex.nie@...uarmicro.com>,
	Dave Martin <dave.martin@....com>,
	Koba Ko <kobak@...dia.com>,
	James Morse <james.morse@....com>
Subject: [RFC PATCH 24/36] arm_mpam: Extend reset logic to allow devices to be reset any time

cpuhp callbacks aren't the only time the MSC configuration may need to
be reset. Resctrl has an API call to reset a class.
If an MPAM error interrupt arrives it indicates the driver has
misprogrammed an MSC. The safest thing to do is reset all the MSCs
and disable MPAM.

Add a helper to reset RIS via their class. Call this from mpam_disable(),
which can be scheduled from the error interrupt handler.

Signed-off-by: James Morse <james.morse@....com>
---
 drivers/platform/arm64/mpam/mpam_devices.c  | 62 ++++++++++++++++++++-
 drivers/platform/arm64/mpam/mpam_internal.h |  1 +
 2 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/drivers/platform/arm64/mpam/mpam_devices.c b/drivers/platform/arm64/mpam/mpam_devices.c
index 2e32e54cc081..145535cd4732 100644
--- a/drivers/platform/arm64/mpam/mpam_devices.c
+++ b/drivers/platform/arm64/mpam/mpam_devices.c
@@ -916,8 +916,6 @@ static int mpam_reset_ris(void *arg)
 	u16 partid, partid_max;
 	struct mpam_msc_ris *ris = arg;
 
-	mpam_assert_srcu_read_lock_held();
-
 	if (ris->in_reset_state)
 		return 0;
 
@@ -1575,6 +1573,66 @@ static void mpam_enable_once(void)
 		READ_ONCE(mpam_partid_max) + 1, mpam_pmg_max + 1);
 }
 
+static void mpam_reset_component_locked(struct mpam_component *comp)
+{
+	int idx;
+	struct mpam_msc *msc;
+	struct mpam_vmsc *vmsc;
+	struct mpam_msc_ris *ris;
+
+	might_sleep();
+	lockdep_assert_cpus_held();
+
+	idx = srcu_read_lock(&mpam_srcu);
+	list_for_each_entry_rcu(vmsc, &comp->vmsc, comp_list) {
+		msc = vmsc->msc;
+
+		list_for_each_entry_rcu(ris, &vmsc->ris, vmsc_list) {
+			if (!ris->in_reset_state)
+				mpam_touch_msc(msc, mpam_reset_ris, ris);
+			ris->in_reset_state = true;
+		}
+	}
+	srcu_read_unlock(&mpam_srcu, idx);
+}
+
+static void mpam_reset_class_locked(struct mpam_class *class)
+{
+	int idx;
+	struct mpam_component *comp;
+
+	lockdep_assert_cpus_held();
+
+	idx = srcu_read_lock(&mpam_srcu);
+	list_for_each_entry_rcu(comp, &class->components, class_list)
+		mpam_reset_component_locked(comp);
+	srcu_read_unlock(&mpam_srcu, idx);
+}
+
+static void mpam_reset_class(struct mpam_class *class)
+{
+	cpus_read_lock();
+	mpam_reset_class_locked(class);
+	cpus_read_unlock();
+}
+
+/*
+ * Called in response to an error IRQ.
+ * All of MPAMs errors indicate a software bug, restore any modified
+ * controls to their reset values.
+ */
+void mpam_disable(void)
+{
+	int idx;
+	struct mpam_class *class;
+
+	idx = srcu_read_lock(&mpam_srcu);
+	list_for_each_entry_srcu(class, &mpam_classes, classes_list,
+				 srcu_read_lock_held(&mpam_srcu))
+		mpam_reset_class(class);
+	srcu_read_unlock(&mpam_srcu, idx);
+}
+
 /*
  * Enable mpam once all devices have been probed.
  * Scheduled by mpam_discovery_cpu_online() once all devices have been created.
diff --git a/drivers/platform/arm64/mpam/mpam_internal.h b/drivers/platform/arm64/mpam/mpam_internal.h
index f3cc88136524..de05eece0a31 100644
--- a/drivers/platform/arm64/mpam/mpam_internal.h
+++ b/drivers/platform/arm64/mpam/mpam_internal.h
@@ -280,6 +280,7 @@ extern u8 mpam_pmg_max;
 
 /* Scheduled work callback to enable mpam once all MSC have been probed */
 void mpam_enable(struct work_struct *work);
+void mpam_disable(void);
 
 int mpam_get_cpumask_from_cache_id(unsigned long cache_id, u32 cache_level,
 				   cpumask_t *affinity);
-- 
2.39.5