From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964905Ab1DNSNW (ORCPT ); Thu, 14 Apr 2011 14:13:22 -0400 Received: from mail.windriver.com ([147.11.1.11]:41973 "EHLO mail.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964943Ab1DNR6T (ORCPT ); Thu, 14 Apr 2011 13:58:19 -0400 From: Paul Gortmaker To: stable@kernel.org, linux-kernel@vger.kernel.org Cc: stable-review@kernel.org, "H. Peter Anvin" , Asit Mallick , Arjan van de Ven , Len Brown , Paul Gortmaker Subject: [34-longterm 155/209] x86, hotplug: In the MWAIT case of play_dead, CLFLUSH the cache line Date: Thu, 14 Apr 2011 13:55:13 -0400 Message-Id: <1302803767-9715-42-git-send-email-paul.gortmaker@windriver.com> X-Mailer: git-send-email 1.7.4.4 In-Reply-To: <1302803767-9715-1-git-send-email-paul.gortmaker@windriver.com> References: <1302803039-9400-1-git-send-email-paul.gortmaker@windriver.com> <1302803767-9715-1-git-send-email-paul.gortmaker@windriver.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: H. Peter Anvin ===================================================================== | This is a commit scheduled for the next v2.6.34 longterm release. | | If you see a problem with using this for longterm, please comment.| ===================================================================== commit ce5f68246bf2385d6174856708d0b746dc378f20 upstream. 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 Acked-by: Venkatesh Pallipadi Cc: Asit Mallick Cc: Arjan van de Ven Cc: Len Brown Signed-off-by: Paul Gortmaker --- 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 b283dbf..9a4fdc5 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1371,9 +1371,12 @@ 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; @@ -1399,10 +1402,25 @@ 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); } -- 1.7.4.4