[RFC PATCH 1/2] perf: arm_spe: Fix consistency of PMSCR register bit CX
Leo Yan
leo.yan at linaro.org
Fri Feb 11 02:45:28 PST 2022
Hi German,
On Thu, Feb 10, 2022 at 05:23:50PM +0000, German Gomez wrote:
[...]
> >>>> One way to fix this is by caching the value of the CX bit during the
> >>>> initialization of the PMU event, so that it remains consistent for the
> >>>> duration of the session.
> >>>>
> >>>> [...]
> > So the patch makes sense to me. Just a minor comment:
> >
> > Here we can define a u64 for recording pmscr value rather than a
> > bool value.
> >
> > struct arm_spe_pmu {
> > ...
> > u64 pmscr;
> > };
>
> I agree with the comment from Will that it makes more sense to store the
> value of the register in the perf_event somehow (due to misunderstanding
> from my side, I thought arm_spe_pmu struct was local to the session).
It's shame that I miss this point :) As you said, struct arm_spe_pmu is
a data structure for Arm SPE device driver instance and it's not
allocated for perf session.
> What about perf_event's void *pmu_private?
Before we use perf_event::pmu_private, could you check the data
structure arm_spe_pmu_buf firstly? This data structure is allocated
when setup AUX ring buffer (so it's allocated for perf session).
IIUC, the function arm_spe_pmu_setup_aux() will be invoked in the perf
process, so it's good for us to initialize pmscr in this function.
Thanks,
Leo
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