Message-ID: <20120509140632.GG22737@aftab.osrc.amd.com>
Date:	Wed, 9 May 2012 16:06:32 +0200
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>,
	Doug Thompson <norsk5@...oo.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>, Tony Luck <tony.luck@...el.com>
Subject: Re: [EDAC ABI v13 04/25] events/hw_event: Create a Hardware Events
 Report Mecanism (HERM)

On Wed, May 09, 2012 at 10:51:05AM -0300, Mauro Carvalho Chehab wrote:
> > Now, if you really want to have a generic mechanism for RAS, used
> > by all the kernel, then I don't have a problem with you adding it
> > to include/ras/hw_event.h or somewhere in that vicinity along with
> > making it generic enough for other users and then taking care of it and
> > developing it to address users' needs.
> 
> I'm ok to move it to include/ras, but, if I remember well from my initial
> tests when I wrote this, several kernel versions ago, there is/was
> a limitation that required that all trace events should be under
> include/trace/events/.
> 
> One other option would be to call it as "include/trace/events/ras.h".
> 
> Steven,
> 
> Would it be possible/recommendable to move this trace header
> to include/linux/ras/hw_event.h?

Oh, yeah, I remember vaguely something like that. Lets wait what Steven
has to say.

> In a matter of fact, my plan is to move the EDAC core to drivers/ras, after
> making it generic enough.

Now that sounds like a very bad idea to me. Why would you do that,
they're just fine under drivers/edac/ the way they are now. If there's
no real reason for doing that, then unnecessary code churn is not what
we want.

[ … ]

> events/hw_event: use a tracepoint-based Hardware Events Report Method (HERM)
> 
> From: Mauro Carvalho Chehab <mchehab@...hat.com>
> 
> Adds a trace class for handle hardware events

You just removed the class - what class now?

> Part of the description bellow is shamelessly copied from Tony
> Luck's notes about the Hardware Error BoF during LPC 2010 [1].
> Tony, thanks for your notes and discussions to generate the
> h/w error reporting requirements.
> 
> [1] http://lwn.net/Articles/416669/
> 
>     We have several subsystems & methods for reporting hardware errors:
> 
>     1) EDAC ("Error Detection and Correction").  In its original form
>     this consisted of a platform specific driver that read topology
>     information and error counts from chipset registers and reported
>     the results via a sysfs interface.
> 
>     2) mcelog - x86 specific decoding of machine check bank registers
>     reporting in binary form via /dev/mcelog. Recent additions make use
>     of the APEI extensions that were documented in version 4.0a of the
>     ACPI specification to acquire more information about errors without
>     having to rely reading chipset registers directly. A user level
>     programs decodes into somewhat human readable format.
> 
>     3) drivers/edac/mce_amd.c - this driver hooks into the mcelog path and
>     decodes errors reported via machine check bank registers in AMD
>     processors to the console log using printk();
> 
>     Each of these mechanisms has a band of followers ... and none
>     of them appear to meet all the needs of all users.
> 
> As part of a hardware event subsystem, let's encapsulate the memory
> error hardware events into a trace facility.
> 
> NOTE: The original patch was providing an additional mechanism for
> MCA-based trace events that also contained MCA error register data.
> Hoever, as no agreement was reached so far for the MCA-based trace
> events, for now, let's add events only for memory errors.
> A latter patch is planned to change the tracepoint, for those types
> of event.
> 
> Reviewed-by: Aristeu Rozanski <arozansk@...hat.com>
> Cc: Doug Thompson <norsk5@...oo.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Ingo Molnar <mingo@...hat.com>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@...hat.com>
> 
> diff --git a/drivers/edac/edac_core.h b/drivers/edac/edac_core.h
> index f06ce9a..eee7360 100644
> --- a/drivers/edac/edac_core.h
> +++ b/drivers/edac/edac_core.h
> @@ -468,7 +468,7 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
>  			  const int layer2,
>  			  const char *msg,
>  			  const char *other_detail,
> -			  const void *mcelog);
> +			  const void *arch_log);
>  
>  /*
>   * edac_device APIs
> diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c
> index e5b5563..eff8266 100644
> --- a/drivers/edac/edac_mc.c
> +++ b/drivers/edac/edac_mc.c
> @@ -33,6 +33,9 @@
>  #include "edac_core.h"
>  #include "edac_module.h"
>  
> +#define CREATE_TRACE_POINTS
> +#include <trace/events/hw_event.h>
> +
>  /* lock to memory controller's control array */
>  static DEFINE_MUTEX(mem_ctls_mutex);
>  static LIST_HEAD(mc_devices);
> @@ -381,6 +384,7 @@ struct mem_ctl_info *edac_mc_alloc(unsigned mc_num,
>  	 * which will perform kobj unregistration and the actual free
>  	 * will occur during the kobject callback operation
>  	 */
> +
>  	return mci;
>  }
>  EXPORT_SYMBOL_GPL(edac_mc_alloc);
> @@ -982,7 +986,7 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
>  			  const int layer2,
>  			  const char *msg,
>  			  const char *other_detail,
> -			  const void *mcelog)
> +			  const void *arch_log)
>  {
>  	/* FIXME: too much for stack: move it to some pre-alocated area */
>  	char detail[80], location[80];
> @@ -1119,21 +1123,27 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
>  	}
>  
>  	/* Memory type dependent details about the error */
> -	if (type == HW_EVENT_ERR_CORRECTED) {
> +	if (type == HW_EVENT_ERR_CORRECTED)
>  		snprintf(detail, sizeof(detail),
>  			"page:0x%lx offset:0x%lx grain:%d syndrome:0x%lx",
>  			page_frame_number, offset_in_page,
>  			grain, syndrome);
> -		edac_ce_error(mci, pos, msg, location, label, detail,
> -			      other_detail, enable_per_layer_report,
> -			      page_frame_number, offset_in_page, grain);
> -	} else {
> +	else
>  		snprintf(detail, sizeof(detail),
>  			"page:0x%lx offset:0x%lx grain:%d",
>  			page_frame_number, offset_in_page, grain);
>  
> +	/* Report the error via the trace interface */
> +	trace_mc_error(type, mci->mc_idx, msg, label, location,
> +		       detail, other_detail);
> +
> +	/* Report the error via the edac_mc_printk() interface */
> +	if (type == HW_EVENT_ERR_CORRECTED)
> +		edac_ce_error(mci, pos, msg, location, label, detail,
> +			      other_detail, enable_per_layer_report,
> +			      page_frame_number, offset_in_page, grain);
> +	else
>  		edac_ue_error(mci, pos, msg, location, label, detail,
>  			      other_detail, enable_per_layer_report);
> -	}
>  }
>  EXPORT_SYMBOL_GPL(edac_mc_handle_error);
> diff --git a/include/trace/events/hw_event.h b/include/trace/events/hw_event.h
> new file mode 100644
> index 0000000..234220a
> --- /dev/null
> +++ b/include/trace/events/hw_event.h
> @@ -0,0 +1,77 @@
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM hw_event
> +
> +#if !defined(_TRACE_HW_EVENT_MC_H) || defined(TRACE_HEADER_MULTI_READ)
> +#define _TRACE_HW_EVENT_MC_H
> +
> +#include <linux/tracepoint.h>
> +#include <linux/edac.h>
> +#include <linux/ktime.h>
> +
> +/*
> + * Hardware Anomaly Report Mecanism (HARM) events

and above says "Hardware Events Report Method (HERM)" The fact that you
yourself are not exactly sure about what this abbreviation is supposed
to be/mean/etc, simply should tell you that it is causing only confusion
with no benefit what-so-ever, even to you!

So stop calling it names and simply say "add a tracepoint for memory
controller errors" and be done with it. There's no need for marketing
speak in the kernel.

> + *
> + * Those events are generated when hardware detected a corrected or
> + * uncorrected event, and are meant to replace the current API to report
> + * errors defined on both EDAC and MCE subsystems.
> + *
> + * FIXME: Add events for handling memory errors originated from the
> + *        MCE subsystem.
> + */
> +
> +/*
> + * Hardware-independent Memory Controller specific events
> + */
> +
> +/*
> + * Default error mechanisms for Memory Controller errors (CE and UE)
> + */
> +TRACE_EVENT(mc_error,
> +
> +	TP_PROTO(const unsigned int err_type,
> +		 const unsigned int mc_index,
> +		 const char *msg,
> +		 const char *label,
> +		 const char *location,
> +		 const char *detail,
> +		 const char *driver_detail),
> +
> +	TP_ARGS(err_type, mc_index, msg, label, location,
> +		detail, driver_detail),
> +
> +	TP_STRUCT__entry(
> +		__field(	unsigned int,	err_type		)
> +		__field(	unsigned int,	mc_index		)
> +		__string(	msg,		msg			)
> +		__string(	label,		label			)
> +		__string(	detail,		detail			)
> +		__string(	location,	location		)
> +		__string(	driver_detail,	driver_detail		)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->err_type		= err_type;
> +		__entry->mc_index		= mc_index;
> +		__assign_str(msg, msg);
> +		__assign_str(label, label);
> +		__assign_str(location, location);
> +		__assign_str(detail, detail);
> +		__assign_str(driver_detail, driver_detail);
> +	),
> +
> +	TP_printk(HW_ERR "mce#%d: %s error %s on memory stick \"%s\" (%s %s %s)",
> +		  __entry->mc_index,
> +		  (__entry->err_type == HW_EVENT_ERR_CORRECTED) ? "Corrected" :
> +			((__entry->err_type == HW_EVENT_ERR_FATAL) ?
> +			"Fatal" : "Uncorrected"),
> +		  __get_str(msg),
> +		  __get_str(label),
> +		  __get_str(location),
> +		  __get_str(detail),
> +		  __get_str(driver_detail))
> +);
> +
> +#endif /* _TRACE_HW_EVENT_MC_H */
> +
> +/* This part must be outside protection */
> +#include <trace/define_trace.h>
> 

-- 
Regards/Gruss,
Boris.

Advanced Micro Devices GmbH
Einsteinring 24, 85609 Dornach
GM: Alberto Bozzo
Reg: Dornach, Landkreis Muenchen
HRB Nr. 43632 WEEE Registernr: 129 19551
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