acpi/tests/avocado/bits/doc: add a doc file to describe the acpi bits test

A doc file is added under docs/devel that describes the purpose of the various
test files and gives guidance to developers on where and how to make changes.

Cc: Daniel P. Berrange" <berrange@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Maydell Peter <peter.maydell@linaro.org>
Cc: John Snow <jsnow@redhat.com>
Cc: Thomas Huth <thuth@redhat.com>
Cc: Alex Bennée <alex.bennee@linaro.org>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Michael Tsirkin <mst@redhat.com>
Signed-off-by: Ani Sinha <ani@anisinha.ca>
Message-Id: <20221021095108.104843-7-ani@anisinha.ca>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

2 files changed, 146 insertions, 0 deletions

diff --git a/docs/devel/acpi-bits.rst b/docs/devel/acpi-bits.rst
new file mode 100644
index 0000000000..c9564d871a
--- /dev/null
+++ b/docs/devel/acpi-bits.rst
@@ -0,0 +1,145 @@
+=============================================================================
+ACPI/SMBIOS avocado tests using biosbits
+=============================================================================
+
+Biosbits is a software written by Josh Triplett that can be downloaded
+from https://biosbits.org/. The github codebase can be found
+`here <https://github.com/biosbits/bits/tree/master>`__. It is a software that executes
+the bios components such as acpi and smbios tables directly through acpica
+bios interpreter (a freely available C based library written by Intel,
+downloadable from https://acpica.org/ and is included with biosbits) without an
+operating system getting involved in between.
+There are several advantages to directly testing the bios in a real physical
+machine or VM as opposed to indirectly discovering bios issues through the
+operating system. For one thing, the OSes tend to hide bios problems from the
+end user. The other is that we have more control of what we wanted to test
+and how by directly using acpica interpreter on top of the bios on a running
+system. More details on the inspiration for developing biosbits and its real
+life uses can be found in [#a]_ and [#b]_.
+This directory contains tests written in python using avocado framework that
+exercises the QEMU bios components using biosbits and reports test failures.
+For QEMU, we maintain a fork of bios bits in gitlab along with all the
+dependent submodules:
+https://gitlab.com/qemu-project/biosbits-bits
+This fork contains numerous fixes, a newer acpica and changes specific to
+running this avocado QEMU tests using bits. The author of this document
+is the sole maintainer of the QEMU fork of bios bits repo.
+
+Under the directory ``tests/avocado/``, ``acpi-bits.py`` is a QEMU avocado
+test that drives all this.
+
+A brief description of the various test files follows.
+
+Under ``tests/avocado/`` as the root we have:
+
+::
+
+   ├── acpi-bits
+   │ ├── bits-config
+   │ │ └── bits-cfg.txt
+   │ ├── bits-tests
+   │ │ ├── smbios.py2
+   │ │ ├── testacpi.py2
+   │ │ └── testcpuid.py2
+   │ └── README
+   ├── acpi-bits.py
+
+* ``tests/avocado``:
+
+   ``acpi-bits.py``:
+   This is the main python avocado test script that generates a
+   biosbits iso. It then spawns a QEMU VM with it, collects the log and reports
+   test failures. This is the script one would be interested in if they wanted
+   to add or change some component of the log parsing, add a new command line
+   to alter how QEMU is spawned etc. Test writers typically would not need to
+   modify this script unless they wanted to enhance or change the log parsing
+   for their tests. In order to enable debugging, you can set **V=1**
+   environment variable. This enables verbose mode for the test and also dumps
+   the entire log from bios bits and more information in case failure happens.
+
+   In order to run this test, please perform the following steps from the QEMU
+   build directory:
+   ::
+
+     $ make check-venv (needed only the first time to create the venv)
+     $ ./tests/venv/bin/avocado run -t acpi tests/avocado
+
+   The above will run all acpi avocado tests including this one.
+   In order to run the individual tests, perform the following:
+   ::
+
+     $ ./tests/venv/bin/avocado run tests/avocado/acpi-bits.py --tap -
+
+   The above will produce output in tap format. You can omit "--tap -" in the
+   end and it will produce output like the following:
+   ::
+
+      $ ./tests/venv/bin/avocado run tests/avocado/acpi-bits.py
+      Fetching asset from tests/avocado/acpi-bits.py:AcpiBitsTest.test_acpi_smbios_bits
+      JOB ID     : eab225724da7b64c012c65705dc2fa14ab1defef
+      JOB LOG    : /home/anisinha/avocado/job-results/job-2022-10-10T17.58-eab2257/job.log
+      (1/1) tests/avocado/acpi-bits.py:AcpiBitsTest.test_acpi_smbios_bits: PASS (33.09 s)
+      RESULTS    : PASS 1 | ERROR 0 | FAIL 0 | SKIP 0 | WARN 0 | INTERRUPT 0 | CANCEL 0
+      JOB TIME   : 39.22 s
+
+   You can inspect the log file for more information about the run or in order
+   to diagnoze issues. If you pass V=1 in the environment, more diagnostic logs
+   would be found in the test log.
+
+* ``tests/avocado/acpi-bits/bits-config``:
+
+   This location contains biosbits configuration files that determine how the
+   software runs the tests.
+
+   ``bits-config.txt``:
+   This is the biosbits config file that determines what tests
+   or actions are performed by bits. The description of the config options are
+   provided in the file itself.
+
+* ``tests/avocado/acpi-bits/bits-tests``:
+
+   This directory contains biosbits python based tests that are run from within
+   the biosbits environment in the spawned VM. New additions of test cases can
+   be made in the appropriate test file. For example, new acpi tests can go
+   into testacpi.py2 and one would call testsuite.add_test() to register the new
+   test so that it gets executed as a part of the ACPI tests.
+   It might be occasionally necessary to disable some subtests or add a new
+   test that belongs to a test suite not already present in this directory. To
+   do this, please clone the bits source from
+   https://gitlab.com/qemu-project/biosbits-bits/-/tree/qemu-bits.
+   Note that this is the "qemu-bits" branch and not the "bits" branch of the
+   repository. "qemu-bits" is the branch where we have made all the QEMU
+   specific enhancements and we must use the source from this branch only.
+   Copy the test suite/script that needs modification (addition of new tests
+   or disabling them) from python directory into this directory. For
+   example, in order to change cpuid related tests, copy the following
+   file into this directory and rename it with .py2 extension:
+   https://gitlab.com/qemu-project/biosbits-bits/-/blob/qemu-bits/python/testcpuid.py
+   Then make your additions and changes here. Therefore, the steps are:
+
+       (a) Copy unmodified test script to this directory from bits source.
+       (b) Add a SPDX license header.
+       (c) Perform modifications to the test.
+
+   Commits (a), (b) and (c) should go under separate commits so that the original
+   test script and the changes we have made are separated and clear.
+
+   The test framework will then use your modified test script to run the test.
+   No further changes would be needed. Please check the logs to make sure that
+   appropriate changes have taken effect.
+
+   The tests have an extension .py2 in order to indicate that:
+
+   (a) They are python2.7 based scripts and not python 3 scripts.
+   (b) They are run from within the bios bits VM and is not subjected to QEMU
+       build/test python script maintainance and dependency resolutions.
+   (c) They need not be loaded by avocado framework when running tests.
+
+
+Author: Ani Sinha <ani@anisinha.ca>
+
+References:
+-----------
+.. [#a] https://blog.linuxplumbersconf.org/2011/ocw/system/presentations/867/original/bits.pdf
+.. [#b] https://www.youtube.com/watch?v=36QIepyUuhg
+
diff --git a/docs/devel/index-build.rst b/docs/devel/index-build.rst
index 1002a533a6..57e8d39d98 100644
--- a/docs/devel/index-build.rst
+++ b/docs/devel/index-build.rst
@@ -11,6 +11,7 @@ the basics if you are adding new files and targets to the build.
    build-system
    kconfig
    testing
+   acpi-bits
    qtest
    ci
    qapi-code-gen