From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with SMTP id 544FA6B0047 for ; Sat, 21 Feb 2009 08:36:17 -0500 (EST) Received: by ey-out-1920.google.com with SMTP id 3so195285eyh.44 for ; Sat, 21 Feb 2009 05:36:14 -0800 (PST) From: Vegard Nossum Subject: [PATCH] kmemcheck: disable fast string operations on P4 CPUs Date: Sat, 21 Feb 2009 14:36:01 +0100 Message-Id: <1235223364-2097-2-git-send-email-vegard.nossum@gmail.com> In-Reply-To: <1235223364-2097-1-git-send-email-vegard.nossum@gmail.com> References: <1235223364-2097-1-git-send-email-vegard.nossum@gmail.com> Sender: owner-linux-mm@kvack.org To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Ingo Molnar , Pekka Enberg List-ID: This patch may allow us to remove the REP emulation code from kmemcheck. Signed-off-by: Vegard Nossum --- arch/x86/kernel/cpu/intel.c | 23 +++++++++++++++++++++++ 1 files changed, 23 insertions(+), 0 deletions(-) diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index 1f137a8..65e9717 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -75,6 +75,29 @@ static void __cpuinit early_init_intel(struct cpuinfo_x86 *c) */ if (c->x86 == 6 && c->x86_model < 15) clear_cpu_cap(c, X86_FEATURE_PAT); + +#ifdef CONFIG_KMEMCHECK + /* + * P4s have a "fast strings" feature which causes single- + * stepping REP instructions to only generate a #DB on + * cache-line boundaries. + * + * Ingo Molnar reported a Pentium D (model 6) and a Xeon + * (model 2) with the same problem. + */ + if (c->x86 == 15) { + u64 misc_enable; + + rdmsrl(MSR_IA32_MISC_ENABLE, misc_enable); + + if (misc_enable & MSR_IA32_MISC_ENABLE_FAST_STRING) { + printk(KERN_INFO "kmemcheck: Disabling fast string operations\n"); + + misc_enable &= ~MSR_IA32_MISC_ENABLE_FAST_STRING; + wrmsrl(MSR_IA32_MISC_ENABLE, misc_enable); + } + } +#endif } #ifdef CONFIG_X86_32 -- 1.6.0.6 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org