linux-kernel - Re: [PATCH] [3/4] x86: MCE: Improve mce_get

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Date:	Fri, 24 Apr 2009 16:52:27 +0800
From:	Huang Ying <ying.huang@...el.com>
To:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
Cc:	Andi Kleen <andi@...stfloor.org>, "hpa@...or.com" <hpa@...or.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"tglx@...utronix.de" <tglx@...utronix.de>
Subject: Re: [PATCH] [3/4] x86: MCE: Improve mce_get_rip

On Fri, 2009-04-24 at 15:28 +0800, Hidetoshi Seto wrote:
> Huang Ying wrote:
> > On Fri, 2009-04-24 at 14:16 +0800, Hidetoshi Seto wrote:
> >> One question is: if (RIPV,EIPV) = (0,0), then is the IP on the stack
> >> really invalid value, or is it still point IP when MCE is generated?
> >> I suppose it is not invalid.  If a processor encounters MCE and if it
> >> is not sure what happened, then it will store the IP on the stack,
> >> indicating neither of flags.
> >>
> >> If this supposition is correct, the best way is pick the value on
> >> the stack unconditionally, and record valid flags together.
> > 
> > According to spec, the IP on stack can be not related to MCE if
> > (RIPV,EIPV) = (0,0). So it is meaningless to report them. If you report
> > them unconditionally, you just push the logic to user space or
> > administrator.
> 
> Sorry, I could not find good page in the spec (Intel64 and IA-32 ASDM)...
> Could you point one?

14.3.1.2 IA32_MCG_STATUS MSR
* EIPV

> I believe that the IP with (RIPV,EIPV) = (1,0) is "not associated with the
> error" too, so is it meaningless to report the IP?
> If you think so then correct fix is replacing RIPV check by EIPV check.

In theory, that is possible (not associated), but I think in practical,
IP with (RIPV,EIPV) = (1,0) is still meaningful as Andi said.

> From another point of view, the reported IP will be one of followings:
>   - IP that associated with error (= related to MCE)
>   - IP that the interrupted program can restart from
>   - IP that when MCE is generated
> Are there no way to distinguish them in user space?

I think you just push same logic to user space.

Best Regards,
Huang Ying


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