linux-kernel - Re: [PATCH v1 2/2] perf bpf filter: Support pre-5.16 kernels

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Message-ID: <CAM9d7cgfkx6VEazYpJEFZ=OTvJL+875_kHShSET4qyN_t9ixkQ@mail.gmail.com>
Date:   Mon, 10 Apr 2023 08:34:34 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org
Subject: Re: [PATCH v1 2/2] perf bpf filter: Support pre-5.16 kernels

On Fri, Apr 7, 2023 at 10:52 PM Ian Rogers <irogers@...gle.com> wrote:
>
> The mem_hops bits were added in 5.16 with no prior equivalent.
>
> Signed-off-by: Ian Rogers <irogers@...gle.com>

Acked-by: Namhyung Kim <namhyung@...nel.org>

Thanks,
Namhyung


> ---
>  tools/perf/util/bpf_skel/sample_filter.bpf.c | 28 ++++++++++++++++++--
>  1 file changed, 26 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/util/bpf_skel/sample_filter.bpf.c b/tools/perf/util/bpf_skel/sample_filter.bpf.c
> index 57e3c67d6d37..cffe493af1ed 100644
> --- a/tools/perf/util/bpf_skel/sample_filter.bpf.c
> +++ b/tools/perf/util/bpf_skel/sample_filter.bpf.c
> @@ -24,6 +24,24 @@ struct perf_sample_data___new {
>         __u64 sample_flags;
>  } __attribute__((preserve_access_index));
>
> +/* new kernel perf_mem_data_src definition */
> +union perf_mem_data_src__new {
> +       __u64 val;
> +       struct {
> +               __u64   mem_op:5,       /* type of opcode */
> +                       mem_lvl:14,     /* memory hierarchy level */
> +                       mem_snoop:5,    /* snoop mode */
> +                       mem_lock:2,     /* lock instr */
> +                       mem_dtlb:7,     /* tlb access */
> +                       mem_lvl_num:4,  /* memory hierarchy level number */
> +                       mem_remote:1,   /* remote */
> +                       mem_snoopx:2,   /* snoop mode, ext */
> +                       mem_blk:3,      /* access blocked */
> +                       mem_hops:3,     /* hop level */
> +                       mem_rsvd:18;
> +       };
> +};
> +
>  /* helper function to return the given perf sample data */
>  static inline __u64 perf_get_sample(struct bpf_perf_event_data_kern *kctx,
>                                     struct perf_bpf_filter_entry *entry)
> @@ -89,8 +107,14 @@ static inline __u64 perf_get_sample(struct bpf_perf_event_data_kern *kctx,
>                         return kctx->data->data_src.mem_dtlb;
>                 if (entry->part == 7)
>                         return kctx->data->data_src.mem_blk;
> -               if (entry->part == 8)
> -                       return kctx->data->data_src.mem_hops;
> +               if (entry->part == 8) {
> +                       union perf_mem_data_src__new *data = (void *)&kctx->data->data_src;
> +
> +                       if (bpf_core_field_exists(data->mem_hops))
> +                               return data->mem_hops;
> +
> +                       return 0;
> +               }
>                 /* return the whole word */
>                 return kctx->data->data_src.val;
>         default:
> --
> 2.40.0.577.gac1e443424-goog
>