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

[Suzuki Kuruppassery Poulose]

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