linux-kernel - Re: [PATCH v2 09/14] perf arm-spe: Refactor counter packet handling

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Date:   Wed, 21 Oct 2020 11:52:12 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     André Przywara <andre.przywara@....com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Wei Li <liwei391@...wei.com>,
        James Clark <james.clark@....com>,
        Dave Martin <Dave.Martin@....com>,
        linux-kernel@...r.kernel.org, Al Grant <Al.Grant@....com>
Subject: Re: [PATCH v2 09/14] perf arm-spe: Refactor counter packet handling

On Tue, Oct 20, 2020 at 10:53:47PM +0100, André Przywara wrote:
> On 29/09/2020 14:39, Leo Yan wrote:
> 
> Hi,
> 
> > This patch defines macros for counter packet header, and uses macro to
> > replace hard code values for packet parsing.
> > 
> > Signed-off-by: Leo Yan <leo.yan@...aro.org>
> > ---
> >  .../util/arm-spe-decoder/arm-spe-pkt-decoder.c  | 17 ++++++++++-------
> >  .../util/arm-spe-decoder/arm-spe-pkt-decoder.h  |  9 +++++++++
> >  2 files changed, 19 insertions(+), 7 deletions(-)
> > 
> > diff --git a/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c b/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
> > index 00a2cd1af422..ed0f4c74dfc5 100644
> > --- a/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
> > +++ b/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
> > @@ -150,10 +150,13 @@ static int arm_spe_get_counter(const unsigned char *buf, size_t len,
> >  			       const unsigned char ext_hdr, struct arm_spe_pkt *packet)
> >  {
> >  	packet->type = ARM_SPE_COUNTER;
> > -	if (ext_hdr)
> > -		packet->index = ((buf[0] & 0x3) << 3) | (buf[1] & 0x7);
> > -	else
> > -		packet->index = buf[0] & 0x7;
> > +	if (ext_hdr) {
> > +		packet->index  = (buf[1] & SPE_CNT_PKT_HDR_INDEX_MASK);
> > +		packet->index |= ((buf[0] & SPE_CNT_PKT_HDR_EXT_INDEX_MASK)
> > +			<< SPE_CNT_PKT_HDR_EXT_INDEX_SHIFT);
> > +	} else {
> > +		packet->index = buf[0] & SPE_CNT_PKT_HDR_INDEX_MASK;
> 
> That looks suspiciously similar to the extended header in the address
> packet. Can you use the same name for that?

Checked for counter packet and address packet, they are using the same
format for index.  Will use the same name.

> And, similar to the address packet, what about:
> 	packet->index |= SPE_PKT_EXT_HEADER_INDEX(buf[0]);

Will do.

> (merging the mask and the shift in the macro definition)
> 
> > +	}
> >  
> >  	return arm_spe_get_payload(buf, len, ext_hdr, packet);
> >  }
> > @@ -431,17 +434,17 @@ int arm_spe_pkt_desc(const struct arm_spe_pkt *packet, char *buf,
> >  			return ret;
> >  
> >  		switch (idx) {
> > -		case 0:
> > +		case SPE_CNT_PKT_HDR_INDEX_TOTAL_LAT:
> >  			ret = arm_spe_pkt_snprintf(&buf, &blen, "TOT");
> >  			if (ret < 0)
> >  				return ret;
> >  			break;
> > -		case 1:
> > +		case SPE_CNT_PKT_HDR_INDEX_ISSUE_LAT:
> >  			ret = arm_spe_pkt_snprintf(&buf, &blen, "ISSUE");
> >  			if (ret < 0)
> >  				return ret;
> >  			break;
> > -		case 2:
> > +		case SPE_CNT_PKT_HDR_INDEX_TRANS_LAT:
> >  			ret = arm_spe_pkt_snprintf(&buf, &blen, "XLAT");
> >  			if (ret < 0)
> >  				return ret;
> > diff --git a/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.h b/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.h
> > index 62db4ff91832..18667a63f5ba 100644
> > --- a/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.h
> > +++ b/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.h
> > @@ -89,6 +89,15 @@ struct arm_spe_pkt {
> >  /* Context packet header */
> >  #define SPE_CTX_PKT_HDR_INDEX_MASK		GENMASK_ULL(1, 0)
> >  
> > +/* Counter packet header */
> > +#define SPE_CNT_PKT_HDR_INDEX_MASK		GENMASK_ULL(2, 0)
> > +#define SPE_CNT_PKT_HDR_INDEX_TOTAL_LAT		(0x0)
> > +#define SPE_CNT_PKT_HDR_INDEX_ISSUE_LAT		(0x1)
> > +#define SPE_CNT_PKT_HDR_INDEX_TRANS_LAT		(0x2)
> 
> I think the Linux kernel coding style does not mention parentheses just
> around numbers, so just 0x2 would suffice, for instance.
> See section 12) in Documentation/process/coding-style.rst

Yeah, it gives example as "#define CONSTANT 0x4000"; will follow the
coding style.

Thanks for suggestions!
Leo