>From 3da1be5c998a8d51f98fdba09b3cb477526c5ff3 Mon Sep 17 00:00:00 2001 From: Scott Bauer Date: Fri, 30 Jan 2015 14:10:37 -0700 Subject: [PATCH] Add check to determine if CLFLUSH is actually necessary before monitor/wait Signed-off-by: Scott Bauer --- arch/x86/kernel/smpboot.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 6d7022c..552ff48 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1384,6 +1384,7 @@ static inline void mwait_play_dead(void) unsigned int highest_subcstate = 0; void *mwait_ptr; int i; + int cpu; if (!this_cpu_has(X86_FEATURE_MWAIT)) return; @@ -1420,6 +1421,7 @@ static inline void mwait_play_dead(void) * content is immaterial as it is not actually modified in any way. */ mwait_ptr = ¤t_thread_info()->flags; + cpu = smp_processor_id(); wbinvd(); @@ -1430,10 +1432,15 @@ static inline void mwait_play_dead(void) * needed, but it should be harmless in either case. * The WBINVD is insufficient due to the spurious-wakeup * case where we return around the loop. + * + * Check if the CLFLUSH is actually necessary before calling */ - mb(); - clflush(mwait_ptr); - mb(); + if (cpu_has_bug(&cpu_data(cpu), X86_BUG_CLFLUSH_MONITOR)) { + mb(); + clflush(mwait_ptr); + mb(); + } + __monitor(mwait_ptr, 0, 0); mb(); __mwait(eax, 0); -- 1.9.1