linux/Documentation/trace/events-msr.rst
Ross Zwisler 2abfcd293b docs: ftrace: always use canonical ftrace path
The canonical location for the tracefs filesystem is at /sys/kernel/tracing.

But, from Documentation/trace/ftrace.rst:

  Before 4.1, all ftrace tracing control files were within the debugfs
  file system, which is typically located at /sys/kernel/debug/tracing.
  For backward compatibility, when mounting the debugfs file system,
  the tracefs file system will be automatically mounted at:

  /sys/kernel/debug/tracing

Many parts of Documentation still reference this older debugfs path, so
let's update them to avoid confusion.

Signed-off-by: Ross Zwisler <zwisler@google.com>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20230125213251.2013791-1-zwisler@google.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2023-01-31 14:02:30 -07:00

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================
MSR Trace Events
================
The x86 kernel supports tracing most MSR (Model Specific Register) accesses.
To see the definition of the MSRs on Intel systems please see the SDM
at https://www.intel.com/sdm (Volume 3)
Available trace points:
/sys/kernel/tracing/events/msr/
Trace MSR reads:
read_msr
- msr: MSR number
- val: Value written
- failed: 1 if the access failed, otherwise 0
Trace MSR writes:
write_msr
- msr: MSR number
- val: Value written
- failed: 1 if the access failed, otherwise 0
Trace RDPMC in kernel:
rdpmc
The trace data can be post processed with the postprocess/decode_msr.py script::
cat /sys/kernel/tracing/trace | decode_msr.py /usr/src/linux/include/asm/msr-index.h
to add symbolic MSR names.