linux-kernel - Re: [PATCH v3 8/9] ACPI, APEI, CPER: Cleanup CPER memory error output format

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Date:	Tue, 22 Oct 2013 10:42:19 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	"Luck, Tony" <tony.luck@...el.com>
Cc:	"Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
	"joe@...ches.com" <joe@...ches.com>,
	"m.chehab@...sung.com" <m.chehab@...sung.com>,
	"arozansk@...hat.com" <arozansk@...hat.com>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Chen Gong <gong.chen@...ux.intel.com>
Subject: Re: [PATCH v3 8/9] ACPI, APEI, CPER: Cleanup CPER memory error
 output format

On Mon, Oct 21, 2013 at 05:14:05PM +0000, Luck, Tony wrote:
> Even if we recovered from a UC error (which is by no means a sure
> thing) ... I don't think the "requires no further action" message
> applies.
>
> Soft single bit errors are common (well, common-ish ... they should
> still be somewhat rare by most objective standard). Double bit errors
> are much rarer ... and are very unlikely to be the result of two
> single bit errors happening to be inside the same cache line. I'd
> recommend further investigation of the source of a UC error (even one
> that is "recovered" in software).

Btw, do we even need to make this distinction? I mean, do we even reach
this path on an error where we need to raise a #MC exception? In the
initial design we were called from machine_check_poll which is not the
exception path and now we're on the decode_chain which gets all errors.

Are we ready to handle all? And also, why do we even need to
differentiate the error types on reporting? I mean, if it is, say, a
contained UC error and we can start a recovery action from userspace
like killing the process, we probably want to have that same detailed
report too?

 [ This is purely hypothetical, of course, as we do the poisoning game
 and killing of processes from kernel space now but still... ]

Thanks.
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