[PATCH 1/2] genirq: Make irq_destroy_ipi take a cpumask of IPIs to destroy

[Matt Redfearn <matt.redfearn@xxxxxxxxxx>]

Previously irq_destroy_ipi() would destroy IPIs to all CPUs that were
configured by irq_reserve_ipi(). This change makes it possible to
destroy just a subset of the IPIs. This may be useful to remove IPIs to
CPUs that have been hot removed so that the IRQ numbers allocated within
the IPI domain can be re-used.

The original behaviour is restored by passing the complete mask that the
IPI was created with.

There are currently no users of this function that would break from the
API change.

Signed-off-by: Matt Redfearn <matt.redfearn@xxxxxxxxxx>
---

 include/linux/irqdomain.h |  2 +-
 kernel/irq/ipi.c          | 18 ++++++++++++++----
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
index 2aed04396210..e1b81d35e7a3 100644
--- a/include/linux/irqdomain.h
+++ b/include/linux/irqdomain.h
@@ -348,7 +348,7 @@ int irq_domain_xlate_onetwocell(struct irq_domain *d, struct device_node *ctrlr,
 /* IPI functions */
 unsigned int irq_reserve_ipi(struct irq_domain *domain,
 			     const struct cpumask *dest);
-void irq_destroy_ipi(unsigned int irq);
+void irq_destroy_ipi(unsigned int irq, const struct cpumask *dest);
 
 /* V2 interfaces to support hierarchy IRQ domains. */
 extern struct irq_data *irq_domain_get_irq_data(struct irq_domain *domain,
diff --git a/kernel/irq/ipi.c b/kernel/irq/ipi.c
index 14777af8e097..bedc995ae214 100644
--- a/kernel/irq/ipi.c
+++ b/kernel/irq/ipi.c
@@ -106,11 +106,12 @@ free_descs:
 /**
  * irq_destroy_ipi() - unreserve an IPI that was previously allocated
  * @irq:	linux irq number to be destroyed
+ * @dest:	cpumask of cpus which should have the IPI removed
  *
  * Return the IPIs allocated with irq_reserve_ipi() to the system destroying
  * all virqs associated with them.
  */
-void irq_destroy_ipi(unsigned int irq)
+void irq_destroy_ipi(unsigned int irq, const struct cpumask *dest)
 {
 	struct irq_data *data = irq_get_irq_data(irq);
 	struct cpumask *ipimask = data ? irq_data_get_affinity_mask(data) : NULL;
@@ -129,10 +130,19 @@ void irq_destroy_ipi(unsigned int irq)
 		return;
 	}
 
-	if (irq_domain_is_ipi_per_cpu(domain))
-		nr_irqs = cpumask_weight(ipimask);
-	else
+	if (WARN_ON(!cpumask_subset(dest, ipimask)))
+		/*
+		 * Must be destroying a subset of CPUs to which this IPI
+		 * was set up to target
+		 */
+		return;
+
+	if (irq_domain_is_ipi_per_cpu(domain)) {
+		irq = irq + cpumask_first(dest) - data->common->ipi_offset;
+		nr_irqs = cpumask_weight(dest);
+	} else {
 		nr_irqs = 1;
+	}
 
 	irq_domain_free_irqs(irq, nr_irqs);
 }
-- 
2.5.0