From 123aa76ec0cab5d4881cd8509faed43231e68801 Mon Sep 17 00:00:00 2001
From: Andi Kleen <andi@firstfloor.org>
Date: Thu, 12 Feb 2009 13:39:27 +0100
Subject: [PATCH] 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 <ak@linux.intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
---
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(-)
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.
*/
--
2.41.3