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

Naveen N. Rao
2013-08-12T12:42:02Z

On 08/12/2013 05:03 PM, Mauro Carvalho Chehab wrote:
> Em Sat, 10 Aug 2013 20:03:22 +0200
> Borislav Petkov <bp@alien8.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@linux.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