Introduce Virtio-loopback epsilon release:

Epsilon release introduces a new compatibility layer which make virtio-loopback
design to work with QEMU and rust-vmm vhost-user backend without require any
changes.

Signed-off-by: Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
Change-Id: I52e57563e08a7d0bdc002f8e928ee61ba0c53dd9

1 files changed, 125 insertions, 0 deletions

diff --git a/docs/tools/qemu-trace-stap.rst b/docs/tools/qemu-trace-stap.rst
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+=========================
+QEMU SystemTap trace tool
+=========================
+
+Synopsis
+--------
+
+**qemu-trace-stap** [*GLOBAL-OPTIONS*] *COMMAND* [*COMMAND-OPTIONS*] *ARGS*...
+
+Description
+-----------
+
+The ``qemu-trace-stap`` program facilitates tracing of the execution
+of QEMU emulators using SystemTap.
+
+It is required to have the SystemTap runtime environment installed to use
+this program, since it is a wrapper around execution of the ``stap``
+program.
+
+Options
+-------
+
+.. program:: qemu-trace-stap
+
+The following global options may be used regardless of which command
+is executed:
+
+.. option:: --verbose, -v
+
+  Display verbose information about command execution.
+
+The following commands are valid:
+
+.. option:: list BINARY PATTERN...
+
+  List all the probe names provided by *BINARY* that match
+  *PATTERN*.
+
+  If *BINARY* is not an absolute path, it will be located by searching
+  the directories listed in the ``$PATH`` environment variable.
+
+  *PATTERN* is a plain string that is used to filter the results of
+  this command. It may optionally contain a ``*`` wildcard to facilitate
+  matching multiple probes without listing each one explicitly. Multiple
+  *PATTERN* arguments may be given, causing listing of probes that match
+  any of the listed names. If no *PATTERN* is given, the all possible
+  probes will be listed.
+
+  For example, to list all probes available in the ``qemu-system-x86_64``
+  binary:
+
+  ::
+
+    $ qemu-trace-stap list qemu-system-x86_64
+
+  To filter the list to only cover probes related to QEMU's cryptographic
+  subsystem, in a binary outside ``$PATH``
+
+  ::
+
+    $ qemu-trace-stap list /opt/qemu/4.0.0/bin/qemu-system-x86_64 'qcrypto*'
+
+.. option:: run OPTIONS BINARY PATTERN...
+
+  Run a trace session, printing formatted output any time a process that is
+  executing *BINARY* triggers a probe matching *PATTERN*.
+
+  If *BINARY* is not an absolute path, it will be located by searching
+  the directories listed in the ``$PATH`` environment variable.
+
+  *PATTERN* is a plain string that matches a probe name shown by the
+  *LIST* command. It may optionally contain a ``*`` wildcard to
+  facilitate matching multiple probes without listing each one explicitly.
+  Multiple *PATTERN* arguments may be given, causing all matching probes
+  to be monitored. At least one *PATTERN* is required, since stap is not
+  capable of tracing all known QEMU probes concurrently without overflowing
+  its trace buffer.
+
+  Invocation of this command does not need to be synchronized with
+  invocation of the QEMU process(es). It will match probes on all
+  existing running processes and all future launched processes,
+  unless told to only monitor a specific process.
+
+  Valid command specific options are:
+
+  .. program:: qemu-trace-stap-run
+
+  .. option:: --pid=PID, -p PID
+
+    Restrict the tracing session so that it only triggers for the process
+    identified by *PID*.
+
+  For example, to monitor all processes executing ``qemu-system-x86_64``
+  as found on ``$PATH``, displaying all I/O related probes:
+
+  ::
+
+    $ qemu-trace-stap run qemu-system-x86_64 'qio*'
+
+  To monitor only the QEMU process with PID 1732
+
+  ::
+
+    $ qemu-trace-stap run --pid=1732 qemu-system-x86_64 'qio*'
+
+  To monitor QEMU processes running an alternative binary outside of
+  ``$PATH``, displaying verbose information about setup of the
+  tracing environment:
+
+  ::
+
+    $ qemu-trace-stap -v run /opt/qemu/4.0.0/qemu-system-x86_64 'qio*'
+
+See also
+--------
+
+:manpage:`qemu(1)`, :manpage:`stap(1)`
+
+..
+  Copyright (C) 2019 Red Hat, Inc.
+
+  This program is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 of the License, or
+  (at your option) any later version.