Re: [PATCH v1 7/7] perf cs-etm: Detect pid in VMID for kernel running at EL2

Suzuki K Poulose
2021-01-11T10:08:08Z

Hi Leo

On 1/9/21 7:44 AM, Leo Yan wrote:
> From: Suzuki K Poulose <suzuki.poulose@arm.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
> context_id is invalid but we have a valid VMID.

Thank you again for cleaning up this ! Please see one comment
below.

>
> Cc: Mike Leach <mike.leach@linaro.org>
> Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
> Cc: Al Grant <al.grant@arm.com>
> Co-developed-by: Leo Yan <leo.yan@linaro.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> Signed-off-by: Leo Yan <leo.yan@linaro.org>
> ---
> .../perf/util/cs-etm-decoder/cs-etm-decoder.c | 32 ++++++++++++++++---
> 1 file changed, 28 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 cd007cc9c283..9e81169dfa76 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@linaro.org>
> */
>
> +#include <linux/coresight-pmu.h>
> #include <linux/err.h>
> #include <linux/list.h>
> #include <linux/zalloc.h>
> @@ -500,13 +501,36 @@ 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;
> + u64 pid_fmt;
> + int ret;
>
> - /* Ignore PE_CONTEXT packets that don't have a valid contextID */
> - if (!elem->context.ctxt_id_valid)
> + ret = cs_etm__get_pid_fmt(trace_chan_id, &pid_fmt);
> + if (ret)
> + return OCSD_RESP_FATAL_SYS_ERR;

The patch looks fine to me. I am wondering if this can be cached somewhere in
the etmq to avoid doing the search everytime we hit a CID ? Surely for a session,
this woudn't change and thus for the decoder life time.

Cheers
Suzuki