[PATCH v2 17/29] arm_mpam: Extend reset logic to allow devices to be reset any time

James Morse
2025-09-10T20:44:56Z

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@arm.com>
---
Changes since v1:
* more complete use of _srcu helpers.
* Use guard macro for srcu.
* Dropped a might_sleep() - something else will bark.
---
drivers/resctrl/mpam_devices.c | 56 ++++++++++++++++++++++++++++++++--
1 file changed, 54 insertions(+), 2 deletions(-)

diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index e7faf453b5d7..a9d3c4b09976 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -842,8 +842,6 @@ 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;

@@ -1340,8 +1338,56 @@ static void mpam_enable_once(void)
mpam_partid_max + 1, mpam_pmg_max + 1);
}

+static void mpam_reset_component_locked(struct mpam_component *comp)
+{
+ struct mpam_msc *msc;
+ struct mpam_vmsc *vmsc;
+ struct mpam_msc_ris *ris;
+
+ lockdep_assert_cpus_held();
+
+ guard(srcu)(&mpam_srcu);
+ list_for_each_entry_srcu(vmsc, &comp->vmsc, comp_list,
+ srcu_read_lock_held(&mpam_srcu)) {
+ msc = vmsc->msc;
+
+ list_for_each_entry_srcu(ris, &vmsc->ris, vmsc_list,
+ srcu_read_lock_held(&mpam_srcu)) {
+ if (!ris->in_reset_state)
+ mpam_touch_msc(msc, mpam_reset_ris, ris);
+ ris->in_reset_state = true;
+ }
+ }
+}
+
+static void mpam_reset_class_locked(struct mpam_class *class)
+{
+ struct mpam_component *comp;
+
+ lockdep_assert_cpus_held();
+
+ guard(srcu)(&mpam_srcu);
+ list_for_each_entry_srcu(comp, &class->components, class_list,
+ srcu_read_lock_held(&mpam_srcu))
+ mpam_reset_component_locked(comp);
+}
+
+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(struct work_struct *ignored)
{
+ int idx;
+ struct mpam_class *class;
struct mpam_msc *msc, *tmp;

mutex_lock(&mpam_cpuhp_state_lock);
@@ -1351,6 +1397,12 @@ void mpam_disable(struct work_struct *ignored)
}
mutex_unlock(&mpam_cpuhp_state_lock);

+ 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);
+
mutex_lock(&mpam_list_lock);
list_for_each_entry_safe(msc, tmp, &mpam_all_msc, all_msc_list)
mpam_msc_destroy(msc);
--
2.39.5