linux-kernel - Re: [PATCH v3 7/8] perf cs-etm: Detect pid in VMID for kernel running at EL2

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Date:   Mon, 8 Feb 2021 13:33:20 -0700
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Leo Yan <leo.yan@...aro.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Jonathan Corbet <corbet@....net>,
        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>,
        Al Grant <al.grant@....com>, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 7/8] perf cs-etm: Detect pid in VMID for kernel
 running at EL2

On Sat, Feb 06, 2021 at 11:08:32PM +0800, Leo Yan wrote:
> From: Suzuki K Poulose <suzuki.poulose@....com>
> 
> The PID of the task could be traced as VMID when the kernel is running
> at EL2.  Teach the decoder to look for VMID when the CONTEXTIDR (Arm32)
> or CONTEXTIDR_EL1 (Arm64) is invalid but we have a valid VMID.
> 
> Cc: Mike Leach <mike.leach@...aro.org>
> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> Cc: Al Grant <al.grant@....com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> Co-developed-by: Leo Yan <leo.yan@...aro.org>
> Signed-off-by: Leo Yan <leo.yan@...aro.org>

Reviewed-by: Mathieu Poirier <mathieu.poirier@...aro.org>

> ---
>  .../perf/util/cs-etm-decoder/cs-etm-decoder.c | 38 +++++++++++++++++--
>  1 file changed, 34 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
> index 3f4bc4050477..4052c9ce6e2f 100644
> --- a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
> +++ b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
> @@ -6,6 +6,7 @@
>   * Author: Mathieu Poirier <mathieu.poirier@...aro.org>
>   */
>  
> +#include <linux/coresight-pmu.h>
>  #include <linux/err.h>
>  #include <linux/list.h>
>  #include <linux/zalloc.h>
> @@ -491,13 +492,42 @@ cs_etm_decoder__set_tid(struct cs_etm_queue *etmq,
>  			const ocsd_generic_trace_elem *elem,
>  			const uint8_t trace_chan_id)
>  {
> -	pid_t tid;
> +	pid_t tid = -1;
> +	static u64 pid_fmt;
> +	int ret;
>  
> -	/* Ignore PE_CONTEXT packets that don't have a valid contextID */
> -	if (!elem->context.ctxt_id_valid)
> +	/*
> +	 * As all the ETMs run at the same exception level, the system should
> +	 * have the same PID format crossing CPUs.  So cache the PID format
> +	 * and reuse it for sequential decoding.
> +	 */
> +	if (!pid_fmt) {
> +		ret = cs_etm__get_pid_fmt(trace_chan_id, &pid_fmt);
> +		if (ret)
> +			return OCSD_RESP_FATAL_SYS_ERR;
> +	}
> +
> +	/*
> +	 * Process the PE_CONTEXT packets if we have a valid contextID or VMID.
> +	 * If the kernel is running at EL2, the PID is traced in CONTEXTIDR_EL2
> +	 * as VMID, Bit ETM_OPT_CTXTID2 is set in this case.
> +	 */
> +	switch (pid_fmt) {
> +	case BIT(ETM_OPT_CTXTID):
> +		if (elem->context.ctxt_id_valid)
> +			tid = elem->context.context_id;
> +		break;
> +	case BIT(ETM_OPT_CTXTID2):
> +		if (elem->context.vmid_valid)
> +			tid = elem->context.vmid;
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	if (tid == -1)
>  		return OCSD_RESP_CONT;
>  
> -	tid =  elem->context.context_id;
>  	if (cs_etm__etmq_set_tid(etmq, tid, trace_chan_id))
>  		return OCSD_RESP_FATAL_SYS_ERR;
>  
> -- 
> 2.25.1
>