@@ -512,6 +512,38 @@ The --itrace option controls the type and frequency of synthesized events
Note that only 64-bit programs are currently supported - further work is
required to support instruction decode of 32-bit Arm programs.
+2.2) Tracing PID
+
+The kernel can be built to write the PID value into the PE ContextID registers.
+For a kernel running at EL1, the PID is stored in CONTEXTIDR_EL1. A PE may
+implement Arm Virtualization Host Extensions (VHE), which the kernel can
+run at EL2 as a virtualisation host; in this case, the PID value is stored in
+CONTEXTIDR_EL2.
+
+perf provides PMU formats that program the ETM to insert these values into the
+trace data; the PMU formats are defined as below:
+
+ "contextid1": Available on both EL1 kernel and EL2 kernel. When the
+ kernel is running at EL1, "contextid1" enables the PID
+ tracing; when the kernel is running at EL2, this enables
+ tracing the PID of guest applications.
+
+ "contextid2": Only usable when the kernel is running at EL2. When
+ selected, enables PID tracing on EL2 kernel.
+
+ "contextid": Will be an alias for the option that enables PID
+ tracing. I.e,
+ contextid == contextid1, on EL1 kernel.
+ contextid == contextid2, on EL2 kernel.
+
+perf will always enable PID tracing at the relevant EL, this is accomplished by
+automatically enable the "contextid" config - but for EL2 it is possible to make
+specific adjustments using configs "contextid1" and "contextid2", E.g. if a user
+wants to trace PIDs for both host and guest, the two configs "contextid1" and
+"contextid2" can be set at the same time:
+
+ perf record -e cs_etm/contextid1,contextid2/u -- vm
+
Generating coverage files for Feedback Directed Optimization: AutoFDO
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