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

Hi Ben,

On 28/07/2025 11:22, Ben Horgan wrote:

On 7/11/25 19:36, James Morse wrote:

quoted

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.

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

quoted

+/*
+ * 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);
+}

Consider moving to the next patch where you introduce interrupt support.

I pulled these changes out of that patch to try and make it simpler!
Doing that would leave a bunch of static functions unused.


Thanks,

James