Documentation: kunit: Reorganize documentation related to running tests

Consolidate documentation running tests into two pages: "run tests with
kunit_tool" and "run tests without kunit_tool".

Signed-off-by: Harinder Singh <sharinder@google.com>
Reviewed-by: Tim Bird <tim.bird@sony.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Link: https://lore.kernel.org/r/20211217044911.798817-5-sharinder@google.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/dev-tools/kunit/index.rst

@@ -10,6 +10,8 @@ KUnit - Linux Kernel Unit Testing
 
 	start
 	architecture
+	run_wrapper
+	run_manual
 	usage
 	kunit-tool
 	api/index
@@ -98,6 +100,8 @@ How do I use it?
 
 *   Documentation/dev-tools/kunit/start.rst - for KUnit new users.
 *   Documentation/dev-tools/kunit/architecture.rst - KUnit architecture.
+*   Documentation/dev-tools/kunit/run_wrapper.rst - run kunit_tool.
+*   Documentation/dev-tools/kunit/run_manual.rst - run tests without kunit_tool.
 *   Documentation/dev-tools/kunit/usage.rst - KUnit features.
 *   Documentation/dev-tools/kunit/tips.rst - best practices with
     examples.

Documentation/dev-tools/kunit/run_manual.rst

@@ -0,0 +1,57 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+============================
+Run Tests without kunit_tool
+============================
+
+If we do not want to use kunit_tool (For example: we want to integrate
+with other systems, or run tests on real hardware), we can
+include KUnit in any kernel, read out results, and parse manually.
+
+.. note:: KUnit is not designed for use in a production system. It is
+          possible that tests may reduce the stability or security of
+          the system.
+
+Configure the Kernel
+====================
+
+KUnit tests can run without kunit_tool. This can be useful, if:
+
+- We have an existing kernel configuration to test.
+- Need to run on real hardware (or using an emulator/VM kunit_tool
+  does not support).
+- Wish to integrate with some existing testing systems.
+
+KUnit is configured with the ``CONFIG_KUNIT`` option, and individual
+tests can also be built by enabling their config options in our
+``.config``. KUnit tests usually (but don't always) have config options
+ending in ``_KUNIT_TEST``. Most tests can either be built as a module,
+or be built into the kernel.
+
+.. note ::
+
+	We can enable the ``KUNIT_ALL_TESTS`` config option to
+	automatically enable all tests with satisfied dependencies. This is
+	a good way of quickly testing everything applicable to the current
+	config.
+
+Once we have built our kernel (and/or modules), it is simple to run
+the tests. If the tests are built-in, they will run automatically on the
+kernel boot. The results will be written to the kernel log (``dmesg``)
+in TAP format.
+
+If the tests are built as modules, they will run when the module is
+loaded.
+
+.. code-block :: bash
+
+	# modprobe example-test
+
+The results will appear in TAP format in ``dmesg``.
+
+.. note ::
+
+	If ``CONFIG_KUNIT_DEBUGFS`` is enabled, KUnit test results will
+	be accessible from the ``debugfs`` filesystem (if mounted).
+	They will be in ``/sys/kernel/debug/kunit/<test_suite>/results``, in
+	TAP format.

Documentation/dev-tools/kunit/run_wrapper.rst

@@ -0,0 +1,247 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=========================
+Run Tests with kunit_tool
+=========================
+
+We can either run KUnit tests using kunit_tool or can run tests
+manually, and then use kunit_tool to parse the results. To run tests
+manually, see: Documentation/dev-tools/kunit/run_manual.rst.
+As long as we can build the kernel, we can run KUnit.
+
+kunit_tool is a Python script which configures and builds a kernel, runs
+tests, and formats the test results.
+
+Run command:
+
+.. code-block::
+
+	./tools/testing/kunit/kunit.py run
+
+We should see the following:
+
+.. code-block::
+
+	Generating .config...
+	Building KUnit kernel...
+	Starting KUnit kernel...
+
+We may want to use the following options:
+
+.. code-block::
+
+	./tools/testing/kunit/kunit.py run --timeout=30 --jobs=`nproc --all
+
+- ``--timeout`` sets a maximum amount of time for tests to run.
+- ``--jobs`` sets the number of threads to build the kernel.
+
+kunit_tool will generate a ``.kunitconfig`` with a default
+configuration, if no other ``.kunitconfig`` file exists
+(in the build directory). In addition, it verifies that the
+generated ``.config`` file contains the ``CONFIG`` options in the
+``.kunitconfig``.
+It is also possible to pass a separate ``.kunitconfig`` fragment to
+kunit_tool. This is useful if we have several different groups of
+tests we want to run independently, or if we want to use pre-defined
+test configs for certain subsystems.
+
+To use a different ``.kunitconfig`` file (such as one
+provided to test a particular subsystem), pass it as an option:
+
+.. code-block::
+
+	./tools/testing/kunit/kunit.py run --kunitconfig=fs/ext4/.kunitconfig
+
+To view kunit_tool flags (optional command-line arguments), run:
+
+.. code-block::
+
+	./tools/testing/kunit/kunit.py run --help
+
+Create a  ``.kunitconfig`` File
+===============================
+
+If we want to run a specific set of tests (rather than those listed
+in the KUnit ``defconfig``), we can provide Kconfig options in the
+``.kunitconfig`` file. For default .kunitconfig, see:
+https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/testing/kunit/configs/default.config.
+A ``.kunitconfig`` is a ``minconfig`` (a .config
+generated by running ``make savedefconfig``), used for running a
+specific set of tests. This file contains the regular Kernel configs
+with specific test targets. The ``.kunitconfig`` also
+contains any other config options required by the tests (For example:
+dependencies for features under tests, configs that enable/disable
+certain code blocks, arch configs and so on).
+
+To create a ``.kunitconfig``, using the KUnit ``defconfig``:
+
+.. code-block::
+
+	cd $PATH_TO_LINUX_REPO
+	cp tools/testing/kunit/configs/default.config .kunit/.kunitconfig
+
+We can then add any other Kconfig options. For example:
+
+.. code-block::
+
+	CONFIG_LIST_KUNIT_TEST=y
+
+kunit_tool ensures that all config options in ``.kunitconfig`` are
+set in the kernel ``.config`` before running the tests. It warns if we
+have not included the options dependencies.
+
+.. note:: Removing something from the ``.kunitconfig`` will
+   not rebuild the ``.config file``. The configuration is only
+   updated if the ``.kunitconfig`` is not a subset of ``.config``.
+   This means that we can use other tools
+   (For example: ``make menuconfig``) to adjust other config options.
+   The build dir needs to be set for ``make menuconfig`` to
+   work, therefore  by default use ``make O=.kunit menuconfig``.
+
+Configure, Build, and Run Tests
+===============================
+
+If we want to make manual changes to the KUnit build process, we
+can run part of the KUnit build process independently.
+When running kunit_tool, from a ``.kunitconfig``, we can generate a
+``.config`` by using the ``config`` argument:
+
+.. code-block::
+
+	./tools/testing/kunit/kunit.py config
+
+To build a KUnit kernel from the current ``.config``, we can use the
+``build`` argument:
+
+.. code-block::
+
+	./tools/testing/kunit/kunit.py build
+
+If we already have built UML kernel with built-in KUnit tests, we
+can run the kernel, and display the test results with the ``exec``
+argument:
+
+.. code-block::
+
+	./tools/testing/kunit/kunit.py exec
+
+The ``run`` command discussed in section: **Run Tests with kunit_tool**,
+is equivalent to running the above three commands in sequence.
+
+Parse Test Results
+==================
+
+KUnit tests output displays results in TAP (Test Anything Protocol)
+format. When running tests, kunit_tool parses this output and prints
+a summary. To see the raw test results in TAP format, we can pass the
+``--raw_output`` argument:
+
+.. code-block::
+
+	./tools/testing/kunit/kunit.py run --raw_output
+
+If we have KUnit results in the raw TAP format, we can parse them and
+print the human-readable summary with the ``parse`` command for
+kunit_tool. This accepts a filename for an argument, or will read from
+standard input.
+
+.. code-block:: bash
+
+	# Reading from a file
+	./tools/testing/kunit/kunit.py parse /var/log/dmesg
+	# Reading from stdin
+	dmesg | ./tools/testing/kunit/kunit.py parse
+
+Run Selected Test Suites
+========================
+
+By passing a bash style glob filter to the ``exec`` or ``run``
+commands, we can run a subset of the tests built into a kernel . For
+example: if we only want to run KUnit resource tests, use:
+
+.. code-block::
+
+	./tools/testing/kunit/kunit.py run 'kunit-resource*'
+
+This uses the standard glob format with wildcard characters.
+
+Run Tests on qemu
+=================
+
+kunit_tool supports running tests on  qemu as well as
+via UML. To run tests on qemu, by default it requires two flags:
+
+- ``--arch``: Selects a configs collection (Kconfig, qemu config options
+  and so on), that allow KUnit tests to be run on the specified
+  architecture in a minimal way. The architecture argument is same as
+  the option name passed to the ``ARCH`` variable used by Kbuild.
+  Not all architectures currently support this flag, but we can use
+  ``--qemu_config`` to handle it. If ``um`` is passed (or this flag
+  is ignored), the tests will run via UML. Non-UML architectures,
+  for example: i386, x86_64, arm and so on; run on qemu.
+
+- ``--cross_compile``: Specifies the Kbuild toolchain. It passes the
+  same argument as passed to the ``CROSS_COMPILE`` variable used by
+  Kbuild. As a reminder, this will be the prefix for the toolchain
+  binaries such as GCC. For example:
+
+  - ``sparc64-linux-gnu`` if we have the sparc toolchain installed on
+    our system.
+
+  - ``$HOME/toolchains/microblaze/gcc-9.2.0-nolibc/microblaze-linux/bin/microblaze-linux``
+    if we have downloaded the microblaze toolchain from the 0-day
+    website to a directory in our home directory called toolchains.
+
+If we want to run KUnit tests on an architecture not supported by
+the ``--arch`` flag, or want to run KUnit tests on qemu using a
+non-default configuration; then we can write our own``QemuConfig``.
+These ``QemuConfigs`` are written in Python. They have an import line
+``from..qemu_config import QemuArchParams`` at the top of the file.
+The file must contain a variable called ``QEMU_ARCH`` that has an
+instance of ``QemuArchParams`` assigned to it. See example in:
+``tools/testing/kunit/qemu_configs/x86_64.py``.
+
+Once we have a ``QemuConfig``, we can pass it into kunit_tool,
+using the ``--qemu_config`` flag. When used, this flag replaces the
+``--arch`` flag. For example: using
+``tools/testing/kunit/qemu_configs/x86_64.py``, the invocation appear
+as
+
+.. code-block:: bash
+
+	./tools/testing/kunit/kunit.py run \
+		--timeout=60 \
+		--jobs=12 \
+		--qemu_config=./tools/testing/kunit/qemu_configs/x86_64.py
+
+To run existing KUnit tests on non-UML architectures, see:
+Documentation/dev-tools/kunit/non_uml.rst.
+
+Command-Line Arguments
+======================
+
+kunit_tool has a number of other command-line arguments which can
+be useful for our test environment. Below the most commonly used
+command line arguments:
+
+- ``--help``: Lists all available options. To list common options,
+  place ``--help`` before the command. To list options specific to that
+  command, place ``--help`` after the command.
+
+  .. note:: Different commands (``config``, ``build``, ``run``, etc)
+            have different supported options.
+- ``--build_dir``: Specifies kunit_tool build directory. It includes
+  the ``.kunitconfig``, ``.config`` files and compiled kernel.
+
+- ``--make_options``: Specifies additional options to pass to make, when
+  compiling a kernel (using ``build`` or ``run`` commands). For example:
+  to enable compiler warnings, we can pass ``--make_options W=1``.
+
+- ``--alltests``: Builds a UML kernel with all config options enabled
+  using ``make allyesconfig``. This allows us to run as many tests as
+  possible.
+
+  .. note:: It is slow and prone to breakage as new options are
+            added or modified. Instead, enable all tests
+            which have satisfied dependencies by adding
+            ``CONFIG_KUNIT_ALL_TESTS=y`` to your ``.kunitconfig``.

Documentation/dev-tools/kunit/start.rst

@@ -20,7 +20,7 @@ can run kunit_tool:
 	./tools/testing/kunit/kunit.py run
 
 For more information on this wrapper, see:
-Documentation/dev-tools/kunit/kunit-tool.rst.
+Documentation/dev-tools/kunit/run_wrapper.rst.
 
 Creating a ``.kunitconfig``
 ---------------------------
@@ -241,6 +241,8 @@ Next Steps
 ==========
 
 *   Documentation/dev-tools/kunit/architecture.rst - KUnit architecture.
+*   Documentation/dev-tools/kunit/run_wrapper.rst - run kunit_tool.
+*   Documentation/dev-tools/kunit/run_manual.rst - run tests without kunit_tool.
 *   Documentation/dev-tools/kunit/usage.rst - KUnit features.
 *   Documentation/dev-tools/kunit/tips.rst - best practices with
     examples.