Re: [PATCH v2 5/7] perf cs-etm: Add helper cs_etm__get_pid_fmt()

On Tue, Feb 02, 2021 at 11:19:22PM +0000, Suzuki Kuruppassery Poulose wrote:

On 2/2/21 4:38 PM, Leo Yan wrote:

quoted

This patch adds helper function cs_etm__get_pid_fmt(), by passing
parameter "traceID", it returns the PID format.

Signed-off-by: Leo Yan <redacted>
---
  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.

Sorry for confusion.  I'd like to rephrase as:

It's possible that the two bits ETM_OPT_CTXTID and ETM_OPT_CTXTID2 are
enabled at the same time when the session runs on an EL2 kernel.  This
means the CONTEXTIDR_EL1 and CONTEXTIDR_EL2 both will be recorded in
the trace data, the tool will selectively use CONTEXTIDR_EL2 as PID.

quoted

+ */
+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)) ?

Actually it's deliberately to set both bits ETM_OPT_CTXTID2 and
ETM_OPT_CTXTID if user has enable configs "contextid1" and
"contextid2".  So this is exactly the reversed flow in the
function cs_etmv4_get_config().

Thanks,
Leo

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