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

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Date:	Sun, 12 Feb 2012 13:48:25 +0100
From:	Borislav Petkov <bp@...64.org>
To:	Mauro Carvalho Chehab <mchehab@...hat.com>
Cc:	Borislav Petkov <bp@...64.org>,
	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)

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.

-- 
Regards/Gruss,
Boris.

Advanced Micro Devices GmbH
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