[PATCH RFC 03/12] genirq: Implement dynamic migration for Managed IRQs

[Qiliang Yuan <realwujing@gmail.com>]

Support dynamic reconfiguration of CPU isolation by making the managed
interrupts responsive to housekeeping mask changes at runtime.

1. Register a housekeeping notifier in the genirq subsystem to listen
   for HK_TYPE_MANAGED_IRQ updates.
2. Iterate through all active interrupts when a mask update occurs.
3. Re-apply affinity for managed interrupts to ensure they honor the
   newly configured housekeeping mask.
4. Use irq_set_affinity_locked() to trigger migration away from newly
   isolated CPUs or towards newly designated housekeeping CPUs.

Signed-off-by: Qiliang Yuan <realwujing@gmail.com>
Signed-off-by: Qiliang Yuan <yuanql9@chinatelecom.cn>
---
 kernel/irq/manage.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 349ae7979da0..9523f0655b12 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -21,6 +21,7 @@
 #include <linux/sched/isolation.h>
 #include <uapi/linux/sched/types.h>
 #include <linux/task_work.h>
+#include <linux/cpuhotplug.h>
 
 #include "internals.h"
 
@@ -2811,3 +2812,54 @@ bool irq_check_status_bit(unsigned int irq, unsigned int bitmask)
 	return res;
 }
 EXPORT_SYMBOL_GPL(irq_check_status_bit);
+
+#ifdef CONFIG_SMP
+static int irq_housekeeping_reconfigure(struct notifier_block *nb,
+					unsigned long action, void *data)
+{
+	struct housekeeping_update *upd = data;
+	struct irq_desc *desc;
+	unsigned int irq;
+
+	if (action != HK_UPDATE_MASK || upd->type != HK_TYPE_MANAGED_IRQ)
+		return NOTIFY_OK;
+
+	irq_lock_sparse();
+	for_each_active_irq(irq) {
+		struct irq_data *id;
+
+		desc = irq_to_desc(irq);
+		if (!desc)
+			continue;
+
+		scoped_guard(raw_spinlock_irqsave, &desc->lock) {
+			id = irq_desc_get_irq_data(desc);
+			if (!irqd_affinity_is_managed(id) || !desc->action ||
+			    !irq_data_get_irq_chip(id))
+				continue;
+
+			/*
+			 * Re-apply existing affinity to honor the new
+			 * housekeeping mask via __irq_set_affinity() logic.
+			 */
+			irq_set_affinity_locked(id, irq_data_get_affinity_mask(id), false);
+		}
+	}
+	irq_unlock_sparse();
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block irq_housekeeping_nb = {
+	.notifier_call = irq_housekeeping_reconfigure,
+};
+
+static int __init irq_init_housekeeping_notifier(void)
+{
+	housekeeping_register_notifier(&irq_housekeeping_nb);
+	return 0;
+}
+core_initcall(irq_init_housekeeping_notifier);
+#endif
+
+

-- 
2.51.0