linux-kernel - Re: [PATCH -v4] x86: MCE: Re-implement MCE log ring buffer as per-CPU ring buffer

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Message-ID: <4A28D738.8010202@jp.fujitsu.com>
Date:	Fri, 05 Jun 2009 17:28:40 +0900
From:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
To:	Huang Ying <ying.huang@...el.com>
CC:	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andi Kleen <ak@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -v4] x86: MCE: Re-implement MCE log ring buffer as per-CPU
 ring buffer

Huang Ying wrote:
> On Fri, 2009-06-05 at 15:01 +0800, Hidetoshi Seto wrote:
>> Huang Ying wrote:
>>>  struct mce_log {
>>> -	char signature[12]; /* "MACHINECHECK" */
>>> +	char signature[12]; /* "MACHINECHEC2" */
>>>  	unsigned len;	    /* = MCE_LOG_LEN */
>>> -	unsigned next;
>>>  	unsigned flags;
>>>  	unsigned pad0;
>>> -	struct mce entry[MCE_LOG_LEN];
>>> +	struct mce_log_cpu *mcelog_cpus;
>>>  };
>> What is this *mcelog_cpus to be used for?
>> It seems it will point one of per-CPU buffers (maybe cpu#0's buffer)
>> if I have read the following mce_log_init() correctly.
> 
> It is mainly used by something like kdump, which can search
> "MACHINECHEC2", and analyze mce_log. mcelog_cpus can help kdump find the
> real mcelog storage.

Hum, but it help tools only to find one of buffers, not to find all.

I think it would be better help for tools if we have another signature
on struct mce_log_cpu, e.g.: 

 +struct mce_log_cpu {
+ 	char signature[**];	/* "MCE_LOG_CPU_VER_1" or so */
+	__u32 cpuid;		/* cpuid or extcpu, same as struct mce */
 +	int head;
 +	int tail;
 +	unsigned long flags;
 +	struct mce entry[MCE_LOG_LEN];
 +};

How about this?


Thanks,
H.Seto

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