[PATCH v4][PART 2 06/10] xen/arm: irq: Restore state of local IRQs during system resume

[Mykola Kvach <xakep.amatop@xxxxxxxxx>]

From: Mykola Kvach <mykola_kvach@xxxxxxxx>

On ARM, the first 32 interrupts (SGIs and PPIs) are banked per-CPU
and not restored by gic_resume (for secondary cpus).

This patch introduces restore_local_irqs_on_resume, a function that
restores the state of local interrupts on the target CPU during
system resume.

It iterates over all local IRQs and re-enables those that were not
disabled, reprogramming their routing and affinity accordingly.

The function is invoked from start_secondary, ensuring that local IRQ
state is restored early during CPU bring-up after suspend.

Signed-off-by: Mykola Kvach <mykola_kvach@xxxxxxxx>
---
 xen/arch/arm/irq.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/xen/arch/arm/irq.c b/xen/arch/arm/irq.c
index 372716a73b..f32f8b56ca 100644
--- a/xen/arch/arm/irq.c
+++ b/xen/arch/arm/irq.c
@@ -113,6 +113,47 @@ static int init_local_irq_data(unsigned int cpu)
     return 0;
 }
 
+/*
+ * The first 32 interrupts (PPIs and SGIs) are per-CPU,
+ * so call this function on the target CPU to restore them.
+ *
+ * SPIs are restored via gic_resume.
+ */
+static void restore_local_irqs_on_resume(void)
+{
+    int irq;
+
+    if ( system_state != SYS_STATE_resume )
+        return;
+
+    spin_lock(&local_irqs_type_lock);
+
+    for ( irq = 0; irq < NR_LOCAL_IRQS; irq++ )
+    {
+        struct irq_desc *desc = irq_to_desc(irq);
+
+        spin_lock(&desc->lock);
+
+        if ( test_bit(_IRQ_DISABLED, &desc->status) )
+        {
+            spin_unlock(&desc->lock);
+            continue;
+        }
+
+        /* it is needed to avoid asserts in below calls */
+        set_bit(_IRQ_DISABLED, &desc->status);
+
+        gic_route_irq_to_xen(desc, GIC_PRI_IRQ);
+
+        /* _IRQ_DISABLED is cleared by below call */
+        desc->handler->startup(desc);
+
+        spin_unlock(&desc->lock);
+    }
+
+    spin_unlock(&local_irqs_type_lock);
+}
+
 static int cpu_callback(struct notifier_block *nfb, unsigned long action,
                         void *hcpu)
 {
@@ -131,6 +172,9 @@ static int cpu_callback(struct notifier_block *nfb, 
unsigned long action,
             printk(XENLOG_ERR "Unable to allocate local IRQ for CPU%u\n",
                    cpu);
         break;
+    case CPU_STARTING:
+        restore_local_irqs_on_resume();
+        break;
     }
 
     return notifier_from_errno(rc);
-- 
2.48.1