Messages in this thread | | | From | Rob Herring <> | Date | Mon, 26 Sep 2022 08:32:21 -0500 | Subject | Re: [PATCH v3 1/3] perf: Skip and warn on unknown format 'configN' attrs |
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On Fri, Sep 16, 2022 at 1:12 PM Namhyung Kim <namhyung@kernel.org> wrote: > > On Wed, Sep 14, 2022 at 1:09 PM Rob Herring <robh@kernel.org> wrote: > > > > If the kernel exposes a new perf_event_attr field in a format attr, perf > > will return an error stating the specified PMU can't be found. For > > example, a format attr with 'config3:0-63' causes an error as config3 is > > unknown to perf. This causes a compatibility issue between a newer > > kernel with older perf tool. > > > > Before this change with a kernel adding 'config3' I get: > > > > $ perf record -e arm_spe// -- true > > event syntax error: 'arm_spe//' > > \___ Cannot find PMU `arm_spe'. Missing kernel support? > > Run 'perf list' for a list of valid events > > > > Usage: perf record [<options>] [<command>] > > or: perf record [<options>] -- <command> [<options>] > > > > -e, --event <event> event selector. use 'perf list' to list > > available events > > > > After this change, I get: > > > > $ perf record -e arm_spe// -- true > > WARNING: 'arm_spe_0' format 'inv_event_filter' requires 'perf_event_attr::config3' which is not supported by this version of perf! > > [ perf record: Woken up 2 times to write data ] > > [ perf record: Captured and wrote 0.091 MB perf.data ] > > > > To support unknown configN formats, rework the YACC implementation to > > pass any config[0-9]+ format to perf_pmu__new_format() to handle with a > > warning. > > It only handles configN formats but it might add a completely different > name later, right?
Right. An unknown configN is a warning. An unknown name is still an error as before. Given that sysfs format attrs are for mapping fields which could be anything to "generic" perf_event_attr fields, how would we ever have anything other than configN?
Rob
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