x64, x2apic/intr-remap: generic irq migration support from process context

Generic infrastructure for migrating the irq from the process context in the
presence of CONFIG_GENERIC_PENDING_IRQ.

This will be used later for migrating irq in the presence of
interrupt-remapping.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: akpm@linux-foundation.org
Cc: arjan@linux.intel.com
Cc: andi@firstfloor.org
Cc: ebiederm@xmission.com
Cc: jbarnes@virtuousgeek.org
Cc: steiner@sgi.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/irq.h

@@ -62,6 +62,7 @@ typedef	void (*irq_flow_handler_t)(unsigned int irq,
 #define IRQ_MOVE_PENDING	0x00200000	/* need to re-target IRQ destination */
 #define IRQ_NO_BALANCING	0x00400000	/* IRQ is excluded from balancing */
 #define IRQ_SPURIOUS_DISABLED	0x00800000	/* IRQ was disabled by the spurious trap */
+#define IRQ_MOVE_PCNTXT	0x01000000	/* IRQ migration from process context */
 
 #ifdef CONFIG_IRQ_PER_CPU
 # define CHECK_IRQ_PER_CPU(var) ((var) & IRQ_PER_CPU)

kernel/irq/manage.c

@@ -87,7 +87,14 @@ int irq_set_affinity(unsigned int irq, cpumask_t cpumask)
 	set_balance_irq_affinity(irq, cpumask);
 
 #ifdef CONFIG_GENERIC_PENDING_IRQ
-	set_pending_irq(irq, cpumask);
+	if (desc->status & IRQ_MOVE_PCNTXT) {
+		unsigned long flags;
+
+		spin_lock_irqsave(&desc->lock, flags);
+		desc->chip->set_affinity(irq, cpumask);
+		spin_unlock_irqrestore(&desc->lock, flags);
+	} else
+		set_pending_irq(irq, cpumask);
 #else
 	desc->affinity = cpumask;
 	desc->chip->set_affinity(irq, cpumask);