Re: [PATCH v1 2/7] perf cs_etm: Use pid tracing explicitly instead of contextid

From: Leo Yan <leo.yan@linaro.org>
To: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Mike Leach <mike.leach@linaro.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	John Garry <john.garry@huawei.com>, Will Deacon <will@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Mark Rutland <mark.rutland@arm.com>, Jiri Olsa <jolsa@redhat.com>,
	Namhyung Kim <namhyung@kernel.org>,
	Daniel Kiss <Daniel.Kiss@arm.com>,
	Denis Nikitin <denik@chromium.org>,
	coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, Al Grant <al.grant@arm.com>
Subject: Re: [PATCH v1 2/7] perf cs_etm: Use pid tracing explicitly instead of contextid
Date: Tue, 19 Jan 2021 10:32:07 +0800	[thread overview]
Message-ID: <20210119023207.GA6483@leoy-ThinkPad-X240s> (raw)
In-Reply-To: <20210115224416.GB375055@xps15>

Hi Mathieu,

On Fri, Jan 15, 2021 at 03:44:16PM -0700, Mathieu Poirier wrote:
> On Sat, Jan 09, 2021 at 03:44:30PM +0800, Leo Yan wrote:
> > From: Suzuki K Poulose <suzuki.poulose@arm.com>
> > 
> > If the kernel is running at EL2, the pid of the task is exposed
> > via VMID instead of the CONTEXTID. Add support for this in the
> > perf tool.
> > 
> > By default the perf tool requests contextid and timestamp for
> > task bound events. Instead of hard coding contextid, switch
> > to "pid" config exposed by the kernel. While at it, define new
> > independent macros (rather than using the "config" bits) for
> > requesting the "pid" and "timestamp" for cs_etm_set_option(),
> > since the PID config is now dynamic depending on the kernel
> > exception level.
> > 
> > Cc: Mike Leach <mike.leach@linaro.org>
> > Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
> > Cc: Al Grant <al.grant@arm.com>
> > Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> > Signed-off-by: Leo Yan <leo.yan@linaro.org>
> > ---
> >  tools/include/linux/coresight-pmu.h | 11 +++--
> >  tools/perf/arch/arm/util/cs-etm.c   | 68 ++++++++++++++++++++++-------
> >  2 files changed, 59 insertions(+), 20 deletions(-)
> > 
> > diff --git a/tools/include/linux/coresight-pmu.h b/tools/include/linux/coresight-pmu.h
> > index b0e35eec6499..927c6285ce5d 100644
> > --- a/tools/include/linux/coresight-pmu.h
> > +++ b/tools/include/linux/coresight-pmu.h
> > @@ -11,16 +11,19 @@
> >  #define CORESIGHT_ETM_PMU_SEED  0x10
> >  
> >  /* ETMv3.5/PTM's ETMCR config bit */
> > -#define ETM_OPT_CYCACC  12
> > -#define ETM_OPT_CTXTID	14
> > -#define ETM_OPT_TS      28
> > -#define ETM_OPT_RETSTK	29
> > +#define ETM_OPT_CYCACC		12
> > +#define ETM_OPT_CTXTID		14
> > +#define ETM_OPT_CTXTID_IN_VMID	15
> > +#define ETM_OPT_TS		28
> > +#define ETM_OPT_RETSTK		29
> >  
> >  /* ETMv4 CONFIGR programming bits for the ETM OPTs */
> >  #define ETM4_CFG_BIT_CYCACC	4
> >  #define ETM4_CFG_BIT_CTXTID	6
> > +#define ETM4_CFG_BIT_VMID	7
> >  #define ETM4_CFG_BIT_TS		11
> >  #define ETM4_CFG_BIT_RETSTK	12
> > +#define ETM4_CFG_BIT_VMID_OPT	15
> 
> Wasn't this done in the previous patch?

In the previous patch, these bits are defined in the kernel's header
include/linux/coresight-pmu.h; at here it defines the same bits in
tool's header.

To be honest, I struggled to understand your suggestions, finally I
think it's feasbile and we can simplify the implementation.  I will
try to refine the patch series for the review.

Appreciate for good suggestions!

Leo