linux-kernel - Re: [PATCH] x86, MCE, AMD: save IA32_MCi_STATUS before machine_check

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Date:	Mon, 29 Sep 2014 14:05:46 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Chen Yucong <slaoub@...il.com>
Cc:	tony.luck@...el.com, linux-edac@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86, MCE, AMD: save IA32_MCi_STATUS before
 machine_check_poll() resets it

On Tue, Sep 23, 2014 at 04:19:14PM +0800, Chen Yucong wrote:
> machine_check_poll() will reset IA32_MCi_STATUS register to zero.
> So we need to save the content of IA32_MCi_STATUS MSRs before
> calling machine_check_poll() for logging threshold interrupt event.
> 
> mce_setup() does not gather the content of IA32_MCG_STATUS, so it
> should be read explicitly.
> 
> Signed-off-by: Chen Yucong <slaoub@...il.com>
> ---
>  arch/x86/kernel/cpu/mcheck/mce_amd.c |   13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/mcheck/mce_amd.c b/arch/x86/kernel/cpu/mcheck/mce_amd.c
> index f8c56bd..9148b4d 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce_amd.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce_amd.c
> @@ -275,6 +275,12 @@ static void amd_threshold_interrupt(void)
>  
>  	mce_setup(&m);
>  
> +	/*
> +	 * mce_setup() can't gather the content of IA32_MCG_STATUS,
> +	 * so it should be read explicitly.
> +	 */

No need for that comment.

> +	rdmsrl(MSR_IA32_MCG_STATUS, m.mcgstatus);
> +
>  	/* assume first bank caused it */
>  	for (bank = 0; bank < mca_cfg.banks; ++bank) {
>  		if (!(per_cpu(bank_map, m.cpu) & (1 << bank)))
> @@ -305,6 +311,12 @@ static void amd_threshold_interrupt(void)
>  			     (high & MASK_LOCKED_HI))
>  				continue;
>  
> +			/*
> +			 * machine_check_poll() will reset IA32_MCi_STATUS
> +			 * register to zero, save it for use later.
> +			 */
> +			rdmsrl(MSR_IA32_MCx_STATUS(bank), m.status);

Actually, to be more future-proof, I'd like to do the AMD-specific
logging first, i.e. before machine_check_poll() so that any future
changes there don't influence what we do in mce_amd.c.

So please move the machine_check_poll() call behind the

	if (high & MASK_OVERFLOW_HI) {

test and drop the return.

But the patch makes sense so good catch!

Thanks.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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