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Diffstat (limited to 'Documentation/trace')
| -rw-r--r-- | Documentation/trace/coresight/coresight.rst | 32 |
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diff --git a/Documentation/trace/coresight/coresight.rst b/Documentation/trace/coresight/coresight.rst index 0b73acb44efa..169749efd8d1 100644 --- a/Documentation/trace/coresight/coresight.rst +++ b/Documentation/trace/coresight/coresight.rst @@ -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 --------------------------------------------------------------------- |