linux-kernel - Re: [PATCH 3/3] mce: acpi/apei: trace: Enable ghes memory error trace event

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Date:	Mon, 12 Aug 2013 18:11:49 +0530
From:	"Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:	Mauro Carvalho Chehab <m.chehab@...sung.com>
CC:	Borislav Petkov <bp@...en8.de>, tony.luck@...el.com,
	bhelgaas@...gle.com, rostedt@...dmis.org, rjw@...k.pl,
	lance.ortiz@...com, linux-pci@...r.kernel.org,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] mce: acpi/apei: trace: Enable ghes memory error trace
 event

On 08/12/2013 05:03 PM, Mauro Carvalho Chehab wrote:
> Em Sat, 10 Aug 2013 20:03:22 +0200
> Borislav Petkov <bp@...en8.de> escreveu:
>
>> On Thu, Aug 08, 2013 at 04:38:22PM -0300, Mauro Carvalho Chehab wrote:
>>> Em Thu, 08 Aug 2013 23:57:51 +0530
>>> "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com> escreveu:
>>>
>>>> Enable memory error trace event in cper.c
>>>
>>> Why do we need to do that? Memory error events are already handled
>>> via edac_ghes module,
>>
>> If APEI gives me all the required information in order to deal with the
>> hardware error - and it looks like it does - then the additional layer
>> of ghes_edac is not needed.
>
> APEI is just the mechanism that collects the data, not the mechanism
> that reports to userspace.

I think what Boris is saying is that ghes_edac isn't adding anything 
more here given what we get from APEI structures. So, there doesn't seem 
to be a need to add dependency on edac for this purpose.

Further, ghes_edac seems to require EDAC_MM_EDAC to be compiled into the 
kernel (not a module). So, more dependencies.

>
> The current implementation is that APEI already reports those errors
> via ghes_edac driver. It also reports the very same error via MCE
> (although the APEI interface to MCE is currently broken for everything
> that it is not Nehalem-EX - as it basically emulates the MCE log for
> that specific architecture).

So, I looked at ghes_edac and it basically seems to boil down to 
trace_mc_event. But, this only seems to expose the APEI data as a string 
and doesn't look to really make all the fields available to user-space 
in a raw manner. Not sure how well this can be utilised by a user-space 
tool. Do you have suggestions on how we can do this?

Thanks,
Naveen

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