linux-kernel - Re: [PATCH v8 2/6] cxl/trace: Add TRACE support for CXL media-error records

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Date:   Mon, 13 Mar 2023 17:21:19 -0700
From:   Alison Schofield <alison.schofield@...el.com>
To:     Ira Weiny <ira.weiny@...el.com>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Ben Widawsky <bwidawsk@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>
Subject: Re: [PATCH v8 2/6] cxl/trace: Add TRACE support for CXL media-error
 records

On Mon, Mar 13, 2023 at 03:47:35PM -0700, Ira Weiny wrote:
> alison.schofield@ wrote:
> > From: Alison Schofield <alison.schofield@...el.com>
> > 
> > CXL devices may support the retrieval of a device poison list.
> > Add a new trace event that the CXL subsystem may use to log
> > the media-error records returned in the poison list.
> > 
> > Log each media-error record as a trace event of type 'cxl_poison'.
> > 
> > Signed-off-by: Alison Schofield <alison.schofield@...el.com>
> > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> > ---
> >  drivers/cxl/core/mbox.c  |  4 +-
> >  drivers/cxl/core/trace.h | 84 ++++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 87 insertions(+), 1 deletion(-)

snip

> > 
> > +#define cxl_poison_overflow(flags, time)				\
> > +	(flags & CXL_POISON_FLAG_OVERFLOW ? le64_to_cpu(time) : 0)
> > +
> > +TRACE_EVENT(cxl_poison,
> > +
> > +	TP_PROTO(struct cxl_memdev *cxlmd, struct cxl_region *region,
> > +		 const struct cxl_poison_record *record,
> > +		 u8 flags, __le64 overflow_t),
> 
> FWIW I made event overflow a separate trace event.
> 
> Will this make all of the poisons in a single GetPoison command marked
> with overflow in the trace buffer?

Yes. Every record returned within a poison payload, gets the same flags and
overflow_t reported in its trace events. 

I took a peek at what you did.  (Perhaps we should have called that
cxl_event_overflow). I don't think the poison reporting allows a
similar, singular overflow trace event. The overflow setting means
the device has overflowed its poison list and the list may be
incomplete. I think we repeat the overflow state on every cxl_poison
trace event until the overflow status goes away. (Scan Media)

Alison


> 
> Ira
> 
> > +
snip

> 
>