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, 92 insertions, 0 deletions

diff --git a/docs/devel/qtest.rst b/docs/devel/qtest.rst
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+========================================
+QTest Device Emulation Testing Framework
+========================================
+
+.. toctree::
+   :hidden:
+
+   qgraph
+
+QTest is a device emulation testing framework.  It can be very useful to test
+device models; it could also control certain aspects of QEMU (such as virtual
+clock stepping), with a special purpose "qtest" protocol.  Refer to
+:ref:`qtest-protocol` for more details of the protocol.
+
+QTest cases can be executed with
+
+.. code::
+
+   make check-qtest
+
+The QTest library is implemented by ``tests/qtest/libqtest.c`` and the API is
+defined in ``tests/qtest/libqtest.h``.
+
+Consider adding a new QTest case when you are introducing a new virtual
+hardware, or extending one if you are adding functionalities to an existing
+virtual device.
+
+On top of libqtest, a higher level library, ``libqos``, was created to
+encapsulate common tasks of device drivers, such as memory management and
+communicating with system buses or devices. Many virtual device tests use
+libqos instead of directly calling into libqtest.
+Libqos also offers the Qgraph API to increase each test coverage and
+automate QEMU command line arguments and devices setup.
+Refer to :ref:`qgraph` for Qgraph explanation and API.
+
+Steps to add a new QTest case are:
+
+1. Create a new source file for the test. (More than one file can be added as
+   necessary.) For example, ``tests/qtest/foo-test.c``.
+
+2. Write the test code with the glib and libqtest/libqos API. See also existing
+   tests and the library headers for reference.
+
+3. Register the new test in ``tests/qtest/meson.build``. Add the test
+   executable name to an appropriate ``qtests_*`` variable. There is
+   one variable per architecture, plus ``qtests_generic`` for tests
+   that can be run for all architectures.  For example::
+
+     qtests_generic = [
+       ...
+       'foo-test',
+       ...
+     ]
+
+4. If the test has more than one source file or needs to be linked with any
+   dependency other than ``qemuutil`` and ``qos``, list them in the ``qtests``
+   dictionary.  For example a test that needs to use the ``QIO`` library
+   will have an entry like::
+
+     {
+       ...
+       'foo-test': [io],
+       ...
+     }
+
+Debugging a QTest failure is slightly harder than the unit test because the
+tests look up QEMU program names in the environment variables, such as
+``QTEST_QEMU_BINARY`` and ``QTEST_QEMU_IMG``, and also because it is not easy
+to attach gdb to the QEMU process spawned from the test. But manual invoking
+and using gdb on the test is still simple to do: find out the actual command
+from the output of
+
+.. code::
+
+  make check-qtest V=1
+
+which you can run manually.
+
+
+.. _qtest-protocol:
+
+QTest Protocol
+--------------
+
+.. kernel-doc:: softmmu/qtest.c
+   :doc: QTest Protocol
+
+
+libqtest API reference
+----------------------
+
+.. kernel-doc:: tests/qtest/libqos/libqtest.h