From: Thomas Gleixner <tglx@linutronix.de>

Date: Fri, 3 Sep 2021 11:24:17 -0400

Subject: genirq: Provide new interfaces for affinity hints

Patch-mainline: v5.17-rc1

Git-commit: 65c7cdedeb3026fabcc967a7aae2f755ad4d0783

References: bsc#1208153

The discussion about removing the side effect of irq_set_affinity_hint() of

actually applying the cpumask (if not NULL) as affinity to the interrupt,

unearthed a few unpleasantries:

  1) The modular perf drivers rely on the current behaviour for the very

     wrong reasons.

  2) While none of the other drivers prevents user space from changing

     the affinity, a cursorily inspection shows that there are at least

     expectations in some drivers.

#1 needs to be cleaned up anyway, so that's not a problem

#2 might result in subtle regressions especially when irqbalanced (which

   nowadays ignores the affinity hint) is disabled.

Provide new interfaces:

  irq_update_affinity_hint()  - Only sets the affinity hint pointer

  irq_set_affinity_and_hint() - Set the pointer and apply the affinity to

                                the interrupt

Make irq_set_affinity_hint() a wrapper around irq_apply_affinity_hint() and

document it to be phased out.

SUSE: For kABI compliance changed this patch to leave irq_set_affinity_hint()

      alone and only add the new interfaces.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Signed-off-by: Nitesh Narayan Lal <nitesh@redhat.com>

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Reviewed-by: Ming Lei <ming.lei@redhat.com>

Link: https://lore.kernel.org/r/20210501021832.743094-1-jesse.brandeburg@intel.com

Link: https://lore.kernel.org/r/20210903152430.244937-2-nitesh@redhat.com

Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>

---

 include/linux/interrupt.h |   42 ++++++++++++++++++++++++++++++++++++++++++

 kernel/irq/manage.c       |   16 ++++++++++++++++

 2 files changed, 58 insertions(+)

--- a/include/linux/interrupt.h

+++ b/include/linux/interrupt.h

@@ -336,6 +336,36 @@ 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_apply_affinity_hint(unsigned int irq, const struct cpumask *m,

+				     bool setaffinity);

+

+/**

+ * irq_update_affinity_hint - Update the affinity hint

+ * @irq:	Interrupt to update

+ * @m:		cpumask pointer (NULL to clear the hint)

+ *

+ * Updates the affinity hint, but does not change the affinity of the interrupt.

+ */

+static inline int

+irq_update_affinity_hint(unsigned int irq, const struct cpumask *m)

+{

+	return __irq_apply_affinity_hint(irq, m, false);

+}

+

+/**

+ * irq_set_affinity_and_hint - Update the affinity hint and apply the provided

+ *			     cpumask to the interrupt

+ * @irq:	Interrupt to update

+ * @m:		cpumask pointer (NULL to clear the hint)

+ *

+ * Updates the affinity hint and if @m is not NULL it applies it as the

+ * affinity of that interrupt.

+ */

+static inline int

+irq_set_affinity_and_hint(unsigned int irq, const struct cpumask *m)

+{

+	return __irq_apply_affinity_hint(irq, m, true);

+}

 extern int

 irq_set_affinity_notifier(unsigned int irq, struct irq_affinity_notify *notify);

@@ -365,6 +395,18 @@ static inline int irq_can_set_affinity(u

 static inline int irq_select_affinity(unsigned int irq)  { return 0; }

+static inline int irq_update_affinity_hint(unsigned int irq,

+					   const struct cpumask *m)

+{

+	return -EINVAL;

+}

+

+static inline int irq_set_affinity_and_hint(unsigned int irq,

+					    const struct cpumask *m)

+{

+	return -EINVAL;

+}

+

 static inline int irq_set_affinity_hint(unsigned int irq,

 					const struct cpumask *m)

 {

--- a/kernel/irq/manage.c

+++ b/kernel/irq/manage.c

@@ -322,6 +322,22 @@ int irq_set_affinity_hint(unsigned int i

 }

 EXPORT_SYMBOL_GPL(irq_set_affinity_hint);

+int __irq_apply_affinity_hint(unsigned int irq, const struct cpumask *m,

+			      bool setaffinity)

+{

+	unsigned long flags;

+	struct irq_desc *desc = irq_get_desc_lock(irq, &flags, IRQ_GET_DESC_CHECK_GLOBAL);

+

+	if (!desc)

+		return -EINVAL;

+	desc->affinity_hint = m;

+	irq_put_desc_unlock(desc, flags);

+	if (m && setaffinity)

+		__irq_set_affinity(irq, m, false);

+	return 0;

+}

+EXPORT_SYMBOL_GPL(__irq_apply_affinity_hint);

+

 static void irq_affinity_notify(struct work_struct *work)

 {

 	struct irq_affinity_notify *notify =