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 <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: [e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

arch/x86/kernel/nmi.c

···
 #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>
···
 
 static DEFINE_PER_CPU(struct nmi_stats, nmi_stats);
 
-static int ignore_nmis;
+static int ignore_nmis __read_mostly;
 
 int unknown_nmi_panic;
 /*