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

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Message-ID: <fd4f4278-fa43-86dc-1f2f-3439f19fea9e@arm.com>
Date:   Mon, 13 Jan 2020 12:27:38 +0000
From:   Suzuki Kuruppassery Poulose <suzuki.poulose@....com>
To:     Leo Yan <leo.yan@...aro.org>, James Clark <james.clark@....com>
Cc:     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

Hi Leo,

On 23/12/2019 03:48, Leo Yan wrote:
> Hi James,
> 
> 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.

As such I don't see any issue with this patch.

Suzuki