diff options
author | H. Peter Anvin <hpa@linux.intel.com> | 2010-09-20 13:04:45 -0700 |
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committer | H. Peter Anvin <hpa@linux.intel.com> | 2010-09-20 15:51:59 -0700 |
commit | ce5f68246bf2385d6174856708d0b746dc378f20 (patch) | |
tree | ba2436cd462a72222a995a6ba887f66232f50843 /arch/x86/kernel/smpboot.c | |
parent | a68e5c94f7d3dd64fef34dd5d97e365cae4bb42a (diff) | |
download | op-kernel-dev-ce5f68246bf2385d6174856708d0b746dc378f20.zip op-kernel-dev-ce5f68246bf2385d6174856708d0b746dc378f20.tar.gz |
x86, hotplug: In the MWAIT case of play_dead, CLFLUSH the cache line
When we're using MWAIT for play_dead, explicitly CLFLUSH the cache
line before executing MONITOR. This is a potential workaround for the
Xeon 7400 erratum AAI65 after having a spurious wakeup and returning
around the loop. "Potential" here because it is not certain that that
erratum could actually trigger; however, the CLFLUSH should be
harmless.
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Acked-by: Venkatesh Pallipadi <venki@google.com>
Cc: Asit Mallick <asit.k.mallick@intel.com>
Cc: Arjan van de Ven <arjan@linux.kernel.org>
Cc: Len Brown <lenb@kernel.org>
Diffstat (limited to 'arch/x86/kernel/smpboot.c')
-rw-r--r-- | arch/x86/kernel/smpboot.c | 20 |
1 files changed, 19 insertions, 1 deletions
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 55c80ffb..fdccfe9 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1394,9 +1394,12 @@ static inline void mwait_play_dead(void) unsigned int highest_cstate = 0; unsigned int highest_subcstate = 0; int i; + void *mwait_ptr; if (!cpu_has(¤t_cpu_data, X86_FEATURE_MWAIT)) return; + if (!cpu_has(¤t_cpu_data, X86_FEATURE_CLFLSH)) + return; if (current_cpu_data.cpuid_level < CPUID_MWAIT_LEAF) return; @@ -1422,10 +1425,25 @@ static inline void mwait_play_dead(void) (highest_subcstate - 1); } + /* + * This should be a memory location in a cache line which is + * unlikely to be touched by other processors. The actual + * content is immaterial as it is not actually modified in any way. + */ + mwait_ptr = ¤t_thread_info()->flags; + wbinvd(); while (1) { - __monitor(¤t_thread_info()->flags, 0, 0); + /* + * The CLFLUSH is a workaround for erratum AAI65 for + * the Xeon 7400 series. It's not clear it is actually + * 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. + */ + clflush(mwait_ptr); + __monitor(mwait_ptr, 0, 0); mb(); __mwait(eax, 0); } |