From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763560AbYHERSe (ORCPT ); Tue, 5 Aug 2008 13:18:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1761981AbYHERRI (ORCPT ); Tue, 5 Aug 2008 13:17:08 -0400 Received: from one.firstfloor.org ([213.235.205.2]:37704 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758092AbYHERRF (ORCPT ); Tue, 5 Aug 2008 13:17:05 -0400 From: Andi Kleen References: <20080805717.971524000@firstfloor.org> In-Reply-To: <20080805717.971524000@firstfloor.org> To: x86@kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] [4/4] MCE: Don't disable machine checks during code patching Message-Id: <20080805171738.9E2F01B90086@one.firstfloor.org> Date: Tue, 5 Aug 2008 19:17:38 +0200 (CEST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This removes part of a a patch I added myself some time ago. After some consideration the patch was a bad idea. In particular it stopped machine check exceptions during code patching. To quote the comment: * MCEs only happen when something got corrupted and in this * case we must do something about the corruption. * Ignoring it is worse than a unlikely patching race. * Also machine checks tend to be broadcast and if one CPU * goes into machine check the others follow quickly, so we don't * expect a machine check to cause undue problems during to code * patching. So undo the machine check related parts of 8f4e956b313dcccbc7be6f10808952345e3b638c NMIs are still disabled. This only removes code, the only additions are a new comment. Signed-off-by: Andi Kleen --- arch/x86/kernel/alternative.c | 17 +++++++++++------ arch/x86/kernel/cpu/mcheck/mce_32.c | 14 -------------- arch/x86/kernel/cpu/mcheck/mce_64.c | 14 -------------- include/asm-x86/mce.h | 2 -- 4 files changed, 11 insertions(+), 36 deletions(-) Index: linux/arch/x86/kernel/alternative.c =================================================================== --- linux.orig/arch/x86/kernel/alternative.c +++ linux/arch/x86/kernel/alternative.c @@ -424,9 +424,17 @@ void __init alternative_instructions(voi that might execute the to be patched code. Other CPUs are not running. */ stop_nmi(); -#ifdef CONFIG_X86_MCE - stop_mce(); -#endif + + /* + * Don't stop machine check exceptions while patching. + * MCEs only happen when something got corrupted and in this + * case we must do something about the corruption. + * Ignoring it is worse than a unlikely patching race. + * Also machine checks tend to be broadcast and if one CPU + * goes into machine check the others follow quickly, so we don't + * expect a machine check to cause undue problems during to code + * patching. + */ apply_alternatives(__alt_instructions, __alt_instructions_end); @@ -466,9 +474,6 @@ void __init alternative_instructions(voi (unsigned long)__smp_locks_end); restart_nmi(); -#ifdef CONFIG_X86_MCE - restart_mce(); -#endif } /** Index: linux/arch/x86/kernel/cpu/mcheck/mce_64.c =================================================================== --- linux.orig/arch/x86/kernel/cpu/mcheck/mce_64.c +++ linux/arch/x86/kernel/cpu/mcheck/mce_64.c @@ -699,20 +699,6 @@ static struct miscdevice mce_log_device &mce_chrdev_ops, }; -static unsigned long old_cr4 __initdata; - -void __init stop_mce(void) -{ - old_cr4 = read_cr4(); - clear_in_cr4(X86_CR4_MCE); -} - -void __init restart_mce(void) -{ - if (old_cr4 & X86_CR4_MCE) - set_in_cr4(X86_CR4_MCE); -} - /* * Old style boot options parsing. Only for compatibility. */ Index: linux/include/asm-x86/mce.h =================================================================== --- linux.orig/include/asm-x86/mce.h +++ linux/include/asm-x86/mce.h @@ -113,8 +113,6 @@ extern void mcheck_init(struct cpuinfo_x #else #define mcheck_init(c) do { } while (0) #endif -extern void stop_mce(void); -extern void restart_mce(void); #endif /* __KERNEL__ */ Index: linux/arch/x86/kernel/cpu/mcheck/mce_32.c =================================================================== --- linux.orig/arch/x86/kernel/cpu/mcheck/mce_32.c +++ linux/arch/x86/kernel/cpu/mcheck/mce_32.c @@ -61,20 +61,6 @@ void mcheck_init(struct cpuinfo_x86 *c) } } -static unsigned long old_cr4 __initdata; - -void __init stop_mce(void) -{ - old_cr4 = read_cr4(); - clear_in_cr4(X86_CR4_MCE); -} - -void __init restart_mce(void) -{ - if (old_cr4 & X86_CR4_MCE) - set_in_cr4(X86_CR4_MCE); -} - static int __init mcheck_disable(char *str) { mce_disabled = 1;