linux-kernel - Re: [PATCH] perf jevents: Fix event syntax error caused by ExtSel

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Message-ID: <CAP-5=fUm4G043v6-pToBiT-psxt-_r4kxtsWwkjLh=ARmhmP_A@mail.gmail.com>
Date:   Wed, 25 May 2022 07:27:08 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     zhengjun.xing@...ux.intel.com
Cc:     acme@...nel.org, peterz@...radead.org, mingo@...hat.com,
        alexander.shishkin@...el.com, jolsa@...hat.com,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        adrian.hunter@...el.com, ak@...ux.intel.com,
        kan.liang@...ux.intel.com
Subject: Re: [PATCH] perf jevents: Fix event syntax error caused by ExtSel

On Wed, May 25, 2022 at 7:04 AM <zhengjun.xing@...ux.intel.com> wrote:
>
> From: Zhengjun Xing <zhengjun.xing@...ux.intel.com>
>
> In the origin code, when "ExtSel" is 1, the eventcode will change to
> "eventcode |= 1 << 21”. For event “UNC_Q_RxL_CREDITS_CONSUMED_VN0.DRS",
> its "ExtSel" is "1", its eventcode will change from 0x1E to 0x20001E,
> but in fact the eventcode should <=0x1FF, so this will cause the parse
> fail:
>
>   # perf stat -e "UNC_Q_RxL_CREDITS_CONSUMED_VN0.DRS" -a sleep 0.1
> event syntax error: '.._RxL_CREDITS_CONSUMED_VN0.DRS'
>                                   \___ value too big for format, maximum is 511
>
> On the perf kernel side, the kernel assumes the valid bits are continuous.
> It will adjust the 0x100 (bit 8 for perf tool) to bit 21 in HW.
>
> DEFINE_UNCORE_FORMAT_ATTR(event_ext, event, "config:0-7,21");
>
> So the perf tool follows the kernel side and just set bit8 other than bit21.
>
> Fixes: fedb2b518239 ("perf jevents: Add support for parsing uncore json files")
> Signed-off-by: Zhengjun Xing <zhengjun.xing@...ux.intel.com>
> Reviewed-by: Kan Liang <kan.liang@...ux.intel.com>

Acked-by: Ian Rogers <irogers@...gle.com>

Thanks,
Ian

> ---
>  tools/perf/pmu-events/jevents.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/perf/pmu-events/jevents.c b/tools/perf/pmu-events/jevents.c
> index cee61c4ed59e..e597e4bac90f 100644
> --- a/tools/perf/pmu-events/jevents.c
> +++ b/tools/perf/pmu-events/jevents.c
> @@ -605,7 +605,7 @@ static int json_events(const char *fn,
>                         } else if (json_streq(map, field, "ExtSel")) {
>                                 char *code = NULL;
>                                 addfield(map, &code, "", "", val);
> -                               eventcode |= strtoul(code, NULL, 0) << 21;
> +                               eventcode |= strtoul(code, NULL, 0) << 8;
>                                 free(code);
>                         } else if (json_streq(map, field, "EventName")) {
>                                 addfield(map, &je.name, "", "", val);
> --
> 2.25.1
>