x86/apic: Provide default send single IPI wrapper

Instead of doing the wrapping in the smp code we can provide a default
wrapper for those APICs which insist on cpumasks.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo 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/20151104220849.631111846@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(int cpu, int vector);
 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);

arch/x86/kernel/apic/ipi.c

@@ -65,6 +65,14 @@ void default_send_IPI_mask_allbutself_phys(const struct cpumask *mask,
 	local_irq_restore(flags);
 }
 
+/*
+ * Helper function for APICs which insist on cpumasks
+ */
+void default_send_IPI_single(int cpu, int vector)
+{
+	apic->send_IPI_mask(cpumask_of(cpu), vector);
+}
+
 #ifdef CONFIG_X86_32
 
 void default_send_IPI_mask_sequence_logical(const struct cpumask *mask,