linux-kernel - Re: [PATCH v3 01/31] events/hw_event: Create a Hardware Events Report Mecanism (HERM)

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Message-ID: <4F37F526.8090907@redhat.com>
Date:	Sun, 12 Feb 2012 15:21:42 -0200
From:	Mauro Carvalho Chehab <mchehab@...hat.com>
To:	Borislav Petkov <bp@...64.org>
CC:	Linux Edac Mailing List <linux-edac@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 01/31] events/hw_event: Create a Hardware Events Report
 Mecanism (HERM)

Em 12-02-2012 10:48, Borislav Petkov escreveu:
> On Fri, Feb 10, 2012 at 12:17:51PM -0200, Mauro Carvalho Chehab wrote:
>> Em 10-02-2012 11:41, Borislav Petkov escreveu:
>>> On Thu, Feb 09, 2012 at 10:01:00PM -0200, Mauro Carvalho Chehab wrote:
>>>> In order to provide a proper hardware event subsystem, let's
>>>> encapsulate hardware events into a common trace facility, and
>>>> make both edac and mce drivers to use it. After that, common
>>>> facilities can be moved into a new core for hardware events
>>>> reporting subsystem. This patch is the first of a series, and just
>>>> touches at mce.
>>>
>>> I think it would work too if you had only one event:
>>>
>>> * trace_hw_error(...)
>>>
>>> which would have as an argument a string describing it, like
>>> "Uncorrected Memory Read Error", "Memory Read Error (out of range)" "TLB
>>> Multimatch Error" etc., followed by the rest of the error info.
>>>
>>> Currently, you're introducing at least 5 trace_* calls _only_ for memory
>>> errors. What about the remaining couples of tens of errors which haven't
>>> been addressed yet?
>>
>> Good point.
>>
>> The way I see it is that:
>>
>> - a non-memory related, non-parsed MCE event would generate a "mce_record" trace
>> 	(we need an additional patch to disable it when the error is parsed.
>> 	 I'll address it after finishing the tests with a few other platforms);
>>
>> As more MCE parsers are added at the core, the situations where such event will
>> be generated will reduce, and will eventually disappear in long term.
>>
>> - a non-x86 event (or a x86 event for a memory controller that is not addressed
>> by MCE events) will use a "mc_error";
>>
>> - a x86 event generated via MCE will use a "mc_error_mce".
>>
>> There are two special events defined when there's a memory error _and_ a driver
>> bug:
>>
>> 	"mc_out_of_range_mce" and "mc_out_of_range".
>>
>> While the name of them and one of the parameters are memory-controller specific,
>> it should be easy to make it generic enough to be used by other types of errors.
>>
>> The previous EDAC logic were to generate an out of range printk and return. With
>> the changes I made, it is possible to let the EDAC to provide the information
>> parsed, just discarding the bad parsed value. That's the approach I took, as the
>> other information there may be useful. By taking such approach, the MCE information
>> will be shown by the "mc_error_mce" trace. So, we can remove the "mc_out_of_range_mce"
>> without loosing any information.
>>
>> In any case, we can't merge the *_mce with the non-mce variant, as the mce.h header
>> is arch specific and doesn't exist on PPC and tilera architectures.
>>
>> So, the only event that we can actually remove is "mc_out_of_range_mce", if we let
>> the core generate two events for badly parsed error events. What do you think?
> 
> As I said already, error messages from the drivers should be something
> very seldom so they don't need a special trace event.
> 
> But most importantly, _ALL_ hw errors could use a single
> trace_hw_error() macro which has a single string argument containing all
> the required error info as a string since the error format is different
> based on the error type. In any case, memory errors are not special! As
> I said also before, we cannot have a trace-call for every error type
> which adds additional information or which might generate an error while
> producing that error info.

All trace events could be resumed into a single string. That's what the
TK_printk macro does.

As I said before, there's just one trace call for memory error events 
(hw_event:mc_error) on my second RFC.

I've added the mce-variant (mc_error_mce) for the version 3 because of what I
understood from the feedback you've provided me in priv, that the mce_record
event should be merged with it. I'm more than happy to remove it, if I
miss-understood you.

Regards,
Mauro.

> 

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