linux-kernel - Re: [PATCH 2/2] x86: re-enable MCE on secondary CPUS after suspend/resume

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Date:	Mon, 15 Dec 2008 23:41:39 +0100
From:	Andreas Herrmann <andreas.herrmann3@....com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] x86: re-enable MCE on secondary CPUS after
	suspend/resume

On Mon, Dec 15, 2008 at 11:33:10PM +0100, Andi Kleen wrote:
> > void __cpuinit mcheck_init(struct cpuinfo_x86 *c)
> > {
> >         static cpumask_t mce_cpus = CPU_MASK_NONE;
> > 
> >         mce_cpu_quirks(c);
> > 
> >         if (mce_dont_init ||
> >             cpu_test_and_set(smp_processor_id(), mce_cpus) ||
> >             !mce_available(c))
> >   =>             return;
> > 
> >         mce_init(NULL);
> >         mce_cpu_features(c);
> > }
> > 
> > But we need to call mce_init to clear all MCE state.
> > IMHO the best location to call mce_init for APs is the cpu notifier.
> 
> Ah got it. Thanks that makes sense. 
> 
> But I think the better fix is to just drop the mce_cpus check and
> then handly it naturally in the standard bootup path. I'm not
> sure what it was good for anyways. I copied it into the 64bit code
> from 32bit, but I suppose even there it isn't really needed and on 
> 32bit it is already gone even.
> 
> How about this patch. Does it fix the problem for you too?

Yup, works as well:

Tested-by: Andreas Herrmann <andreas.herrmann3@....com>


Thanks,

Andreas

> -Andi
> 
> --
> 
> 
> Don't prevent multiple initialization of MCEs.
> 
> Back from early prehistory mcheck_init() has a reentry check. Presumably
> that was needed in very old kernels to prevent it entering twice.
> 
> But as Andreas points out this prevents CPU hotplug (and therefore resume)
> to correctly reinitialize MCEs when a AP boots again after being
> offlined. 
> 
> Just drop the check.
> 
> Based on a report from Andreas Herrmann
> 
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> 
> ---
>  arch/x86/kernel/cpu/mcheck/mce_64.c |    3 ---
>  1 file changed, 3 deletions(-)
> 
> Index: linux/arch/x86/kernel/cpu/mcheck/mce_64.c
> ===================================================================
> --- linux.orig/arch/x86/kernel/cpu/mcheck/mce_64.c	2008-12-15 23:13:02.000000000 +0100
> +++ linux/arch/x86/kernel/cpu/mcheck/mce_64.c	2008-12-15 23:13:44.000000000 +0100
> @@ -510,12 +510,9 @@
>   */
>  void __cpuinit mcheck_init(struct cpuinfo_x86 *c)
>  {
> -	static cpumask_t mce_cpus = CPU_MASK_NONE;
> -
>  	mce_cpu_quirks(c);
>  
>  	if (mce_dont_init ||
> -	    cpu_test_and_set(smp_processor_id(), mce_cpus) ||
>  	    !mce_available(c))
>  		return;
>  
> 


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