[PATCH v4 5/5] perf cs-etm: Detect pid in VMID for kernel running at EL2

[Leo Yan]

From: Suzuki K Poulose <suzuki.poulose at 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 CONTEXTIDR (Arm32)
or CONTEXTIDR_EL1 (Arm64) is invalid but we have a valid VMID.

Cc: Mike Leach <mike.leach at linaro.org>
Cc: Mathieu Poirier <mathieu.poirier at linaro.org>
Cc: Al Grant <al.grant at arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose at arm.com>
Co-developed-by: Leo Yan <leo.yan at linaro.org>
Signed-off-by: Leo Yan <leo.yan at linaro.org>
Reviewed-by: Mathieu Poirier <mathieu.poirier at linaro.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 at linaro.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