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x86, mce: don't disable machine checks during code patching

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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
8f4e956b31 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>
This commit is contained in:
Andi Kleen 2009-02-12 13:39:27 +01:00 committed by H. Peter Anvin
parent 973a2dd1d5
commit 123aa76ec0
4 changed files with 11 additions and 36 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/x86/include/asm/mce.h
View File

@ -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 */

17
arch/x86/kernel/alternative.c
View File

@ -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
}
/**

14
arch/x86/kernel/cpu/mcheck/mce_32.c
View File

@ -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;

14
arch/x86/kernel/cpu/mcheck/mce_64.c
View File

@ -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.
*/