Re: [PATCH v2 4/7] perf cs-etm: Support PID tracing in config

[Mike Leach]

On Tue, 2 Feb 2021 at 16:39, Leo Yan <leo.yan@xxxxxxxxxx> wrote:
>
> From: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
>
> If the kernel is running at EL2, the pid of a task is exposed via VMID
> instead of the CONTEXTID.  Add support for this in the perf tool.
>
> This patch respects user setting if user has specified any configs
> from "contextid", "contextid1" or "contextid2"; otherwise, it
> dynamically sets config based on PMU format "contextid".
>
> Cc: Mike Leach <mike.leach@xxxxxxxxxx>
> Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
> Cc: Al Grant <al.grant@xxxxxxx>
> Co-developed-by: Leo Yan <leo.yan@xxxxxxxxxx>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> Signed-off-by: Leo Yan <leo.yan@xxxxxxxxxx>
> ---
>  tools/include/linux/coresight-pmu.h |  3 ++
>  tools/perf/arch/arm/util/cs-etm.c   | 61 +++++++++++++++++++++++------
>  2 files changed, 52 insertions(+), 12 deletions(-)
>
> diff --git a/tools/include/linux/coresight-pmu.h b/tools/include/linux/coresight-pmu.h
> index 5dc47cfdcf07..4ac5c081af93 100644
> --- a/tools/include/linux/coresight-pmu.h
> +++ b/tools/include/linux/coresight-pmu.h
> @@ -20,14 +20,17 @@
>   */
>  #define ETM_OPT_CYCACC         12
>  #define ETM_OPT_CTXTID         14
> +#define ETM_OPT_CTXTID2                15
>  #define ETM_OPT_TS             28
>  #define ETM_OPT_RETSTK         29
>
>  /* ETMv4 CONFIGR programming bits for the ETM OPTs */
>  #define ETM4_CFG_BIT_CYCACC    4
>  #define ETM4_CFG_BIT_CTXTID    6
> +#define ETM4_CFG_BIT_VMID      7
>  #define ETM4_CFG_BIT_TS                11
>  #define ETM4_CFG_BIT_RETSTK    12
> +#define ETM4_CFG_BIT_VMID_OPT  15
>
>  static inline int coresight_get_trace_id(int cpu)
>  {
> diff --git a/tools/perf/arch/arm/util/cs-etm.c b/tools/perf/arch/arm/util/cs-etm.c
> index c25c878fd06c..fa6f91a7c8a1 100644
> --- a/tools/perf/arch/arm/util/cs-etm.c
> +++ b/tools/perf/arch/arm/util/cs-etm.c
> @@ -67,6 +67,7 @@ static int cs_etm_set_context_id(struct auxtrace_record *itr,
>         char path[PATH_MAX];
>         int err = -EINVAL;
>         u32 val;
> +       u64 contextid;
>
>         ptr = container_of(itr, struct cs_etm_recording, itr);
>         cs_etm_pmu = ptr->cs_etm_pmu;
> @@ -86,25 +87,59 @@ static int cs_etm_set_context_id(struct auxtrace_record *itr,
>                 goto out;
>         }
>
> +       /* User has configured for PID tracing, respects it. */
> +       contextid = evsel->core.attr.config &
> +                       (BIT(ETM_OPT_CTXTID) | BIT(ETM_OPT_CTXTID2));
> +
>         /*
> -        * TRCIDR2.CIDSIZE, bit [9-5], indicates whether contextID tracing
> -        * is supported:
> -        *  0b00000 Context ID tracing is not supported.
> -        *  0b00100 Maximum of 32-bit Context ID size.
> -        *  All other values are reserved.
> +        * If user doesn't configure the contextid format, parse PMU format and
> +        * enable PID tracing according to the "contextid" format bits:
> +        *
> +        *   If bit ETM_OPT_CTXTID is set, trace CONTEXTIDR_EL1;
> +        *   If bit ETM_OPT_CTXTID2 is set, trace CONTEXTIDR_EL2.
>          */
> -       val = BMVAL(val, 5, 9);
> -       if (!val || val != 0x4) {
> -               err = -EINVAL;
> -               goto out;
> +       if (!contextid)
> +               contextid = perf_pmu__format_bits(&cs_etm_pmu->format,
> +                                                 "contextid");
> +
> +       if (contextid & BIT(ETM_OPT_CTXTID)) {
> +               /*
> +                * TRCIDR2.CIDSIZE, bit [9-5], indicates whether contextID
> +                * tracing is supported:
> +                *  0b00000 Context ID tracing is not supported.
> +                *  0b00100 Maximum of 32-bit Context ID size.
> +                *  All other values are reserved.
> +                */
> +               val = BMVAL(val, 5, 9);
> +               if (!val || val != 0x4) {
> +                       pr_err("%s: CONTEXTIDR_EL1 isn't supported\n",
> +                              CORESIGHT_ETM_PMU_NAME);
> +                       err = -EINVAL;
> +                       goto out;
> +               }
> +       }
> +
> +       if (contextid & BIT(ETM_OPT_CTXTID2)) {
> +               /*
> +                * TRCIDR2.VMIDOPT[30:29] != 0 and
> +                * TRCIDR2.VMIDSIZE[14:10] == 0b00100 (32bit virtual contextid)
> +                * We can't support CONTEXTIDR in VMID if the size of the
> +                * virtual context id is < 32bit.
> +                * Any value of VMIDSIZE >= 4 (i.e, > 32bit) is fine for us.
> +                */
> +               if (!BMVAL(val, 29, 30) || BMVAL(val, 10, 14) < 4) {
> +                       pr_err("%s: CONTEXTIDR_EL2 isn't supported\n",
> +                              CORESIGHT_ETM_PMU_NAME);
> +                       err = -EINVAL;
> +                       goto out;
> +               }
>         }
>
>         /* All good, let the kernel know */
> -       evsel->core.attr.config |= (1 << ETM_OPT_CTXTID);
> +       evsel->core.attr.config |= contextid;
>         err = 0;
>
>  out:
> -
>         return err;
>  }
>
> @@ -489,7 +524,9 @@ static u64 cs_etmv4_get_config(struct auxtrace_record *itr)
>                 config |= BIT(ETM4_CFG_BIT_TS);
>         if (config_opts & BIT(ETM_OPT_RETSTK))
>                 config |= BIT(ETM4_CFG_BIT_RETSTK);
> -
> +       if (config_opts & BIT(ETM_OPT_CTXTID2))
> +               config |= BIT(ETM4_CFG_BIT_VMID) |
> +                         BIT(ETM4_CFG_BIT_VMID_OPT);
>         return config;
>  }
>
> --
> 2.25.1
>

reviewed-by: Mike Leach <mike.leach@xxxxxxxxxx>


--
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK