Re: [PATCH v2 1/3] genirq/affinity: Add irq_update_affinity_desc()

[Thomas Gleixner]

On Mon, Nov 02 2020 at 21:35, Thomas Gleixner wrote:
> On Mon, Nov 02 2020 at 17:32, John Garry wrote:
> Correct. I have a halfways working solution for that, but I need to fix
> some other thing first.

Sorry for the delay. Supporting this truly on x86 needs some more
thought and surgery, but for ARM it should not matter. I made a few
tweaks to your original code. See below.

Thanks,

        tglx
---
From: John Garry <john.garry@xxxxxxxxxx>
Subject: genirq/affinity: Add irq_update_affinity_desc()
Date: Wed, 28 Oct 2020 20:33:05 +0800

From: John Garry <john.garry@xxxxxxxxxx>

Add a function to allow the affinity of an interrupt be switched to
managed, such that interrupts allocated for platform devices may be
managed.

Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: John Garry <john.garry@xxxxxxxxxx>
---
 include/linux/interrupt.h |    8 ++++++
 kernel/irq/manage.c       |   56 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 64 insertions(+)

--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -352,6 +352,8 @@ extern int irq_can_set_affinity(unsigned
 extern int irq_select_affinity(unsigned int irq);
 
 extern int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m);
+extern int irq_update_affinity_desc(unsigned int irq,
+				    struct irq_affinity_desc *affinity);
 
 extern int
 irq_set_affinity_notifier(unsigned int irq, struct irq_affinity_notify *notify);
@@ -386,6 +388,12 @@ static inline int irq_set_affinity_hint(
 {
 	return -EINVAL;
 }
+
+static inline int irq_update_affinity_desc(unsigned int irq,
+					   struct irq_affinity_desc *affinity)
+{
+	return -EINVAL;
+}
 
 static inline int
 irq_set_affinity_notifier(unsigned int irq, struct irq_affinity_notify *notify)
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -371,6 +371,62 @@ int irq_set_affinity_locked(struct irq_d
 	return ret;
 }
 
+/**
+ * irq_update_affinity_desc - Update affinity management for an interrupt
+ * @irq:	The interrupt number to update
+ * @affinity:	Pointer to the affinity descriptor
+ *
+ * This interface can be used to configure the affinity management of
+ * interrupts which have been allocated already.
+ */
+int irq_update_affinity_desc(unsigned int irq,
+			     struct irq_affinity_desc *affinity)
+{
+	struct irq_desc *desc;
+	unsigned long flags;
+	bool activated;
+
+	/*
+	 * Supporting this with the reservation scheme used by x86 needs
+	 * some more thought. Fail it for now.
+	 */
+	if (IS_ENABLED(CONFIG_GENERIC_IRQ_RESERVATION_MODE))
+		return -EOPNOTSUPP;
+
+	desc = irq_get_desc_buslock(irq, &flags, 0);
+	if (!desc)
+		return -EINVAL;
+
+	/* Requires the interrupt to be shut down */
+	if (irqd_is_started(&desc->irq_data))
+		return -EBUSY;
+
+	/* Interrupts which are already managed cannot be modified */
+	if (irqd_is_managed(&desc->irq_data))
+		return -EBUSY;
+
+	/*
+	 * Deactivate the interrupt. That's required to undo
+	 * anything an earlier activation has established.
+	 */
+	activated = irqd_is_activated(&desc->irq_data);
+	if (activated)
+		irq_domain_deactivate_irq(&desc->irq_data);
+
+	if (affinity->is_managed) {
+		irqd_set(&desc->irq_data, IRQD_AFFINITY_MANAGED);
+		irqd_set(&desc->irq_data, IRQD_MANAGED_SHUTDOWN);
+	}
+
+	cpumask_copy(desc->irq_common_data.affinity, &affinity->mask);
+
+	/* Restore the activation state */
+	if (activated)
+		irq_domain_deactivate_irq(&desc->irq_data);
+	irq_put_desc_busunlock(desc, flags);
+	return 0;
+}
+
 int __irq_set_affinity(unsigned int irq, const struct cpumask *mask, bool force)
 {
 	struct irq_desc *desc = irq_to_desc(irq);