Messages in this thread | | | Date | Fri, 29 Sep 2017 17:19:40 -0500 | From | Kim Phillips <> | Subject | Re: [PATCH v5 6/7] drivers/perf: Add support for ARMv8.2 Statistical Profiling Extension |
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On Thu, 28 Sep 2017 15:09:50 +0100 Will Deacon <will.deacon@arm.com> wrote:
> +/* Perf callbacks */ > +static int arm_spe_pmu_event_init(struct perf_event *event) > +{ > + u64 reg; > + struct perf_event_attr *attr = &event->attr; > + struct arm_spe_pmu *spe_pmu = to_spe_pmu(event->pmu); > + > + /* This is, of course, deeply driver-specific */ > + if (attr->type != event->pmu->type) > + return -ENOENT; > + > + if (event->cpu >= 0 && > + !cpumask_test_cpu(event->cpu, &spe_pmu->supported_cpus)) > + return -ENOENT;
So -ENOENT will make tools/perf/util/evsel.c tell the user "The %s event is not supported." whereas returning -ENODEV will say "No such device - did you specify an out-of-range profile CPU?" which may or may not be more appropriate for this check.
> + if (arm_spe_event_to_pmsevfr(event) & SYS_PMSEVFR_EL1_RES0) > + return -EOPNOTSUPP; > + if (attr->exclude_idle) > + return -EOPNOTSUPP;
"PMU Hardware doesn't support sampling/overflow-interrupts." will be printed if the user didn't specify a sample period. Otherwise, a string with "/bin/dmesg may provide additional information." will be printed.
I was hoping for a response from acme by now for this:
https://www.spinics.net/lists/linux-perf-users/msg04066.html
Alas, nothing. Looking at the #ifdef x86 in evsel.c, I'm guessing it'll be ok, although I'm still not sure how PMU-specific we can get in evsel.c, nor whether it's ok to communicate lists of h/w supported sample periods through /sys/bus/event_source/devices/...
acme? OK to refactor evsel messaging for Arm, including parsing for which PMUs are being used, so customize the message?
Kim
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