x86/apic: Implement default single target IPI function

apic_physflat and bigsmp_apic can share that implementation.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NIngo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Borislav Petkov <bp@alien.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Travis <travis@sgi.com>
Cc: Daniel J Blueman <daniel@numascale.com>
Link: http://lkml.kernel.org/r/20151104220848.898543767@linutronix.de

arch/x86/include/asm/ipi.h

@@ -119,6 +119,7 @@ static inline void
 	native_apic_mem_write(APIC_ICR, cfg);
 }
 
+extern void default_send_IPI_single_phys(int cpu, int vector);
 extern void default_send_IPI_mask_sequence_phys(const struct cpumask *mask,
 						 int vector);
 extern void default_send_IPI_mask_allbutself_phys(const struct cpumask *mask,

arch/x86/kernel/apic/ipi.c

@@ -18,6 +18,16 @@
 #include <asm/proto.h>
 #include <asm/ipi.h>
 
+void default_send_IPI_single_phys(int cpu, int vector)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	__default_send_IPI_dest_field(per_cpu(x86_cpu_to_apicid, cpu),
+				      vector, APIC_DEST_PHYSICAL);
+	local_irq_restore(flags);
+}
+
 void default_send_IPI_mask_sequence_phys(const struct cpumask *mask, int vector)
 {
 	unsigned long query_cpu;