linux-kernel - Re: [PATCH] perf tools: Fix bug when recording SPE and non SPE events

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Date:   Mon, 13 Jan 2020 22:58:03 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Suzuki Kuruppassery Poulose <suzuki.poulose@....com>
Cc:     James Clark <james.clark@....com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        nd@....com, Mathieu Poirier <mathieu.poirier@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Igor Lubashev <ilubashe@...mai.com>
Subject: Re: [PATCH] perf tools: Fix bug when recording SPE and non SPE events

On Mon, Jan 13, 2020 at 10:17:51PM +0800, Leo Yan wrote:

[...]

> > > On Fri, Dec 20, 2019 at 11:05:25AM +0000, James Clark wrote:
> > > > This patch fixes an issue when non Arm SPE events are specified after an
> > > > Arm SPE event. In that case, perf will exit with an error code and not
> > > > produce a record file. This is because a loop index is used to store the
> > > > location of the relevant Arm SPE PMU, but if non SPE PMUs follow, that
> > > > index will be overwritten. Fix this issue by saving the PMU into a
> > > > variable instead of using the index, and also add an error message.
> > > > 
> > > > Before the fix:
> > > >      ./perf record -e arm_spe/ts_enable=1/ -e branch-misses ls; echo $?
> > > >      237
> > > > 
> > > > After the fix:
> > > >      ./perf record -e arm_spe/ts_enable=1/ -e branch-misses ls; echo $?
> > > >      ...
> > > >      0
> > > 
> > > Just bring up a question related with PMU event registration.  Let's
> > > see the DT binding in arch/arm64/boot/dts/arm/fvp-base-revc.dts:
> > > 
> > >           spe-pmu {
> > >                   compatible = "arm,statistical-profiling-extension-v1";
> > >                   interrupts = <GIC_PPI 5 IRQ_TYPE_LEVEL_HIGH>;
> > >           };
> > > 
> > > 
> > > Now SPE registers PMU event for every CPU; seem to me, though SPE is an
> > 
> > Do you mean "SPE PMU" here ? SPE is different from ETM, where the trace
> > data is micro-architecture dependent. And thus you cannot mix the trace
> > on different CPUs with different micro-archs.
> 
> Understood that SPE is micro-architecture dependent.

Maybe SPE is more general than we think :)

Since SPE is defined in ARMv8 architecture reference manual (ARM DDI
0487D.a); should SPE trace data format is unified and defined in Chapter
D9 "Statistical Profiling Extension Sample Record Specification"?

Thanks,
Leo