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

On Mon, Jan 11, 2021 at 10:07:03AM +0000, Suzuki Kuruppassery Poulose wrote:

Hi Leo

On 1/9/21 7:44 AM, Leo Yan wrote:

quoted

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.

Welcome!

quoted

Cc: Mike Leach <redacted>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Al Grant <redacted>
Co-developed-by: Leo Yan <redacted>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Leo Yan <redacted>
---
  .../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.

Good suggestion, will refine for this in next version.

Thanks,
Leo

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