Re: [PATCH 7/7] perf arm-spe: Don't hard code config attribute

Leo Yan
2025-12-02T12:42:50Z

On Tue, Dec 02, 2025 at 12:28:35PM +0000, Coresight ML wrote:
> On Mon, Dec 01, 2025 at 04:41:10PM +0000, Coresight ML wrote:
> > Use the config attribute that's published by the driver instead of
> > hard coding "attr.config".
> >
> > Signed-off-by: James Clark <james.clark@linaro.org>
> > ---
> > tools/perf/arch/arm64/util/arm-spe.c | 15 ++++++++-------
> > 1 file changed, 8 insertions(+), 7 deletions(-)
> >
> > diff --git a/tools/perf/arch/arm64/util/arm-spe.c b/tools/perf/arch/arm64/util/arm-spe.c
> > index d5ec1408d0ae..6c3dc97fde30 100644
> > --- a/tools/perf/arch/arm64/util/arm-spe.c
> > +++ b/tools/perf/arch/arm64/util/arm-spe.c
> > @@ -256,7 +256,7 @@ static __u64 arm_spe_pmu__sample_period(const struct perf_pmu *arm_spe_pmu)
> >
> > static void arm_spe_setup_evsel(struct evsel *evsel, struct perf_cpu_map *cpus)
> > {
> > - u64 bit;
> > + u64 pa_enable_bit;
> >
> > evsel->core.attr.freq = 0;
> > evsel->core.attr.sample_period = arm_spe_pmu__sample_period(evsel->pmu);
> > @@ -288,9 +288,10 @@ static void arm_spe_setup_evsel(struct evsel *evsel, struct perf_cpu_map *cpus)
> > * inform that the resulting output's SPE samples contain physical addresses
> > * where applicable.
> > */
> > - bit = perf_pmu__format_bits(evsel->pmu, "pa_enable");
> > - if (evsel->core.attr.config & bit)
> > - evsel__set_sample_bit(evsel, PHYS_ADDR);
> > +
> > + if (!evsel__get_config_val(evsel->pmu, evsel, "pa_enable", &pa_enable_bit))
> > + if (pa_enable_bit)
> > + evsel__set_sample_bit(evsel, PHYS_ADDR);
>
> Hmm... I am a bit concerned for the evsel__get_config_val() usage
> throughout the series.
>
> evsel__get_config_val() returns a whole config value rather than the
> bit field specified by the format name. If other bits (but not the
> "pa_enable" bit) are set in the same config set, would it wrongly set
> the PHYS_ADDR sample bit?

I saw you used FIELD_GET() to read specific bit field in
evsel__get_config_val(). This is not concerned anymore.

Sorry for noise.

> Seems to me, for reading specific format, perf_pmu__format_bits() is
> more suitable than evsel__get_config_val().

For me, this comment is still valid, given perf_pmu__format_bits()
will always exist.

Thanks,
Leo