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Commit 123aa76e authored by Andi Kleen's avatar Andi Kleen Committed by H. Peter Anvin
Browse files

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
8f4e956b NMIs are still disabled.

This only removes code, the only additions are a new comment.

Signed-off-by: default avatarAndi Kleen <ak@linux.intel.com>
Acked-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
parent 973a2dd1

arch/x86/include/asm/mce.h

+0 −2
Original line number Diff line number Diff line
@@ -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 */

arch/x86/kernel/alternative.c

+11 −6
Original line number Diff line number Diff line
@@ -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

}



/**

arch/x86/kernel/cpu/mcheck/mce_32.c

+0 −14
Original line number Diff line number Diff line
@@ -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;

arch/x86/kernel/cpu/mcheck/mce_64.c

+0 −14
Original line number Diff line number Diff line
@@ -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.

 */