genirq: Introduce IRQD_MANAGED_SHUTDOWN

Affinity managed interrupts should keep their assigned affinity accross CPU
hotplug. To avoid magic hackery in device drivers, the core code shall
manage them transparently. This will set these interrupts into a managed
shutdown state when the last CPU of the assigned affinity mask goes
offline. The interrupt will be restarted when one of the CPUs in the
assigned affinity mask comes back online.

Introduce the necessary state flag and the accessor functions.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>
Link: http://lkml.kernel.org/r/20170619235446.954523476@linutronix.de

include/linux/irq.h

@@ -207,6 +207,8 @@ struct irq_data {
  * IRQD_FORWARDED_TO_VCPU	- The interrupt is forwarded to a VCPU
  * IRQD_AFFINITY_MANAGED	- Affinity is auto-managed by the kernel
  * IRQD_IRQ_STARTED		- Startup state of the interrupt
+ * IRQD_MANAGED_SHUTDOWN	- Interrupt was shutdown due to empty affinity
+ *				  mask. Applies only to affinity managed irqs.
  */
 enum {
 	IRQD_TRIGGER_MASK		= 0xf,
@@ -225,6 +227,7 @@ enum {
 	IRQD_FORWARDED_TO_VCPU		= (1 << 20),
 	IRQD_AFFINITY_MANAGED		= (1 << 21),
 	IRQD_IRQ_STARTED		= (1 << 22),
+	IRQD_MANAGED_SHUTDOWN		= (1 << 23),
 };
 
 #define __irqd_to_state(d) ACCESS_PRIVATE((d)->common, state_use_accessors)
@@ -343,6 +346,11 @@ static inline bool irqd_is_started(struct irq_data *d)
 	return __irqd_to_state(d) & IRQD_IRQ_STARTED;
 }
 
+static inline bool irqd_is_managed_shutdown(struct irq_data *d)
+{
+	return __irqd_to_state(d) & IRQD_MANAGED_SHUTDOWN;
+}
+
 #undef __irqd_to_state
 
 static inline irq_hw_number_t irqd_to_hwirq(struct irq_data *d)

kernel/irq/internals.h

@@ -193,6 +193,16 @@ static inline void irqd_clr_move_pending(struct irq_data *d)
 	__irqd_to_state(d) &= ~IRQD_SETAFFINITY_PENDING;
 }
 
+static inline void irqd_set_managed_shutdown(struct irq_data *d)
+{
+	__irqd_to_state(d) |= IRQD_MANAGED_SHUTDOWN;
+}
+
+static inline void irqd_clr_managed_shutdown(struct irq_data *d)
+{
+	__irqd_to_state(d) &= ~IRQD_MANAGED_SHUTDOWN;
+}
+
 static inline void irqd_clear(struct irq_data *d, unsigned int mask)
 {
 	__irqd_to_state(d) &= ~mask;