x86/nmi: Mark 'ignore_nmis' as __read_mostly

ignore_nmis is used in two distinct places:

 1. modified through {stop,restart}_nmi by alternative_instructions
 2. read by do_nmi to determine if default_do_nmi should be called or not

thus the access pattern conforms to __read_mostly and do_nmi() is a fastpath.
Signed-off-by: Kostenzer Felix <fkostenzer@live.at>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/nmi.c

@@ -30,6 +30,7 @@
 #include <asm/nmi.h>
 #include <asm/x86_init.h>
 #include <asm/reboot.h>
+#include <asm/cache.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/nmi.h>
@@ -69,7 +70,7 @@ struct nmi_stats {
 
 static DEFINE_PER_CPU(struct nmi_stats, nmi_stats);
 
-static int ignore_nmis;
+static int ignore_nmis __read_mostly;
 
 int unknown_nmi_panic;
 /*