From 123aa76ec0cab5d4881cd8509faed43231e68801 Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Thu, 12 Feb 2009 13:39:27 +0100 Subject: x86, mce: don't disable machine checks during code patching Impact: low priority bug fix 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 Acked-by: Thomas Gleixner Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/mce.h | 2 -- arch/x86/kernel/alternative.c | 17 +++++++++++------ arch/x86/kernel/cpu/mcheck/mce_32.c | 14 -------------- arch/x86/kernel/cpu/mcheck/mce_64.c | 14 -------------- 4 files changed, 11 insertions(+), 36 deletions(-) (limited to 'arch') diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h index 32c6e17b960..5522273a3ad 100644 --- a/arch/x86/include/asm/mce.h +++ b/arch/x86/include/asm/mce.h @@ -120,8 +120,6 @@ extern void mcheck_init(struct cpuinfo_x86 *c); #else #define mcheck_init(c) do { } while (0) #endif -extern void stop_mce(void); -extern void restart_mce(void); #endif /* __KERNEL__ */ #endif /* _ASM_X86_MCE_H */ diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index a84ac7b570e..5b8394a3a6b 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -414,9 +414,17 @@ void __init alternative_instructions(void) 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); @@ -456,9 +464,6 @@ void __init alternative_instructions(void) (unsigned long)__smp_locks_end); restart_nmi(); -#ifdef CONFIG_X86_MCE - restart_mce(); -#endif } /** diff --git a/arch/x86/kernel/cpu/mcheck/mce_32.c b/arch/x86/kernel/cpu/mcheck/mce_32.c index dfaebce3633..3552119b091 100644 --- a/arch/x86/kernel/cpu/mcheck/mce_32.c +++ b/arch/x86/kernel/cpu/mcheck/mce_32.c @@ -60,20 +60,6 @@ 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; diff --git a/arch/x86/kernel/cpu/mcheck/mce_64.c b/arch/x86/kernel/cpu/mcheck/mce_64.c index 5ed80991ab9..25ccdbec86e 100644 --- a/arch/x86/kernel/cpu/mcheck/mce_64.c +++ b/arch/x86/kernel/cpu/mcheck/mce_64.c @@ -680,20 +680,6 @@ 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. */ -- cgit v1.2.3