linux-kernel - Re: [PATCH v2 5/7] perf cs-etm: Add helper cs_etm__get_pid

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Date:   Tue, 2 Feb 2021 23:19:22 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Leo Yan <leo.yan@...aro.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Mike Leach <mike.leach@...aro.org>,
        Jonathan Corbet <corbet@....net>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        John Garry <john.garry@...wei.com>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Daniel Kiss <Daniel.Kiss@....com>,
        Denis Nikitin <denik@...omium.org>, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/7] perf cs-etm: Add helper cs_etm__get_pid_fmt()

On 2/2/21 4:38 PM, Leo Yan wrote:
> This patch adds helper function cs_etm__get_pid_fmt(), by passing
> parameter "traceID", it returns the PID format.
> 
> Signed-off-by: Leo Yan <leo.yan@...aro.org>
> ---
>   tools/perf/util/cs-etm.c | 43 ++++++++++++++++++++++++++++++++++++++++
>   tools/perf/util/cs-etm.h |  1 +
>   2 files changed, 44 insertions(+)
> 
> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
> index a2a369e2fbb6..8194ddbd01e5 100644
> --- a/tools/perf/util/cs-etm.c
> +++ b/tools/perf/util/cs-etm.c
> @@ -7,6 +7,7 @@
>    */
>   
>   #include <linux/bitops.h>
> +#include <linux/coresight-pmu.h>
>   #include <linux/err.h>
>   #include <linux/kernel.h>
>   #include <linux/log2.h>
> @@ -156,6 +157,48 @@ int cs_etm__get_cpu(u8 trace_chan_id, int *cpu)
>   	return 0;
>   }
>   
> +/*
> + * The returned PID format is presented by two bits:
> + *
> + *   Bit ETM_OPT_CTXTID: CONTEXTIDR or CONTEXTIDR_EL1 is traced;
> + *   Bit ETM_OPT_CTXTID2: CONTEXTIDR_EL2 is traced.
> + *
> + * It's possible that these two bits are set together, this means the tracing
> + * contains PIDs for both CONTEXTIDR_EL1 and CONTEXTIDR_EL2.

This is a bit confusing. If both the bits are set, the session
was run on an EL2 kernel. Thus, the PID is always in CONTEXTIDR_EL2.

> + */
> +int cs_etm__get_pid_fmt(u8 trace_chan_id, u64 *pid_fmt)
> +{
> +	struct int_node *inode;
> +	u64 *metadata, val;
> +
> +	inode = intlist__find(traceid_list, trace_chan_id);
> +	if (!inode)
> +		return -EINVAL;
> +
> +	metadata = inode->priv;
> +
> +	if (metadata[CS_ETM_MAGIC] == __perf_cs_etmv3_magic) {
> +		val = metadata[CS_ETM_ETMCR];
> +		/* CONTEXTIDR is traced */
> +		if (val & BIT(ETM_OPT_CTXTID))
> +			*pid_fmt = BIT(ETM_OPT_CTXTID);
> +	} else {
> +		val = metadata[CS_ETMV4_TRCCONFIGR];
> +
> +		*pid_fmt = 0;
> +
> +		/* CONTEXTIDR_EL2 is traced */
> +		if (val & (BIT(ETM4_CFG_BIT_VMID) | BIT(ETM4_CFG_BIT_VMID_OPT)))
> +			*pid_fmt = BIT(ETM_OPT_CTXTID2);
> +
> +		/* CONTEXTIDR_EL1 is traced */
> +		if (val & BIT(ETM4_CFG_BIT_CTXTID))

I haven't looked at how this gets used. But, Shouldn't this be :

		else if (val & BIT(ETM4_CFG_BIT_CTXTID)) ?

Suzuki