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Documentation: kunit: Add some troubleshooting tips to the FAQ 

Add an FAQ entry to the KUnit documentation with some tips for
troubleshooting KUnit and kunit_tool.

These suggestions largely came from an email thread:
https://lore.kernel.org/linux-kselftest/41db8bbd-3ba0-8bde-7352-083bf4b947ff@intel.com/T/#m23213d4e156db6d59b0b460a9014950f5ff6eb03

Signed-off-by: David Gow <davidgow@google.com>
Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
This commit is contained in:
David Gow 2020-06-02 20:37:25 -07:00 committed by Shuah Khan
parent ee61492ab9
commit c63d2dd7e1
1 changed files with 40 additions and 0 deletions
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Documentation/dev-tools/kunit/faq.rst
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@ -61,3 +61,43 @@ test, or an end-to-end test.
kernel by installing a production configuration of the kernel on production
hardware with a production userspace and then trying to exercise some behavior
that depends on interactions between the hardware, the kernel, and userspace.
KUnit isn't working, what should I do?
======================================
Unfortunately, there are a number of things which can break, but here are some
things to try.
1. Try running ``./tools/testing/kunit/kunit.py run`` with the ``--raw_output``
parameter. This might show details or error messages hidden by the kunit_tool
parser.
2. Instead of running ``kunit.py run``, try running ``kunit.py config``,
``kunit.py build``, and ``kunit.py exec`` independently. This can help track
down where an issue is occurring. (If you think the parser is at fault, you
can run it manually against stdin or a file with ``kunit.py parse``.)
3. Running the UML kernel directly can often reveal issues or error messages
kunit_tool ignores. This should be as simple as running ``./vmlinux`` after
building the UML kernel (e.g., by using ``kunit.py build``). Note that UML
has some unusual requirements (such as the host having a tmpfs filesystem
mounted), and has had issues in the past when built statically and the host
has KASLR enabled. (On older host kernels, you may need to run ``setarch
`uname -m` -R ./vmlinux`` to disable KASLR.)
4. Make sure the kernel .config has ``CONFIG_KUNIT=y`` and at least one test
(e.g. ``CONFIG_KUNIT_EXAMPLE_TEST=y``). kunit_tool will keep its .config
around, so you can see what config was used after running ``kunit.py run``.
It also preserves any config changes you might make, so you can
enable/disable things with ``make ARCH=um menuconfig`` or similar, and then
re-run kunit_tool.
5. Try to run ``make ARCH=um defconfig`` before running ``kunit.py run``. This
may help clean up any residual config items which could be causing problems.
6. Finally, try running KUnit outside UML. KUnit and KUnit tests can run be
built into any kernel, or can be built as a module and loaded at runtime.
Doing so should allow you to determine if UML is causing the issue you're
seeing. When tests are built-in, they will execute when the kernel boots, and
modules will automatically execute associated tests when loaded. Test results
can be collected from ``/sys/kernel/debug/kunit/<test suite>/results``, and
can be parsed with ``kunit.py parse``. For more details, see "KUnit on
non-UML architectures" in :doc:`usage`.
If none of the above tricks help, you are always welcome to email any issues to
kunit-dev@googlegroups.com.