Documentation: kunit: document support for QEMU in kunit_tool

Document QEMU support, what it does, and how to use it in kunit_tool.

Signed-off-by: Brendan Higgins <brendanhiggins@google.com>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

1 files changed, 39 insertions, 11 deletions

diff --git a/Documentation/dev-tools/kunit/usage.rst b/Documentation/dev-tools/kunit/usage.rst
index 650f99590df5..888c341701da 100644
--- a/Documentation/dev-tools/kunit/usage.rst
+++ b/Documentation/dev-tools/kunit/usage.rst
@@ -609,17 +609,45 @@ non-UML architectures:
 None of these are reasons not to run your KUnit tests on real hardware; they are
 only things to be aware of when doing so.
 
-The biggest impediment will likely be that certain KUnit features and
-infrastructure may not support your target environment. For example, at this
-time the KUnit Wrapper (``tools/testing/kunit/kunit.py``) does not work outside
-of UML. Unfortunately, there is no way around this. Using UML (or even just a
-particular architecture) allows us to make a lot of assumptions that make it
-possible to do things which might otherwise be impossible.
-
-Nevertheless, all core KUnit framework features are fully supported on all
-architectures, and using them is straightforward: all you need to do is to take
-your kunitconfig, your Kconfig options for the tests you would like to run, and
-merge them into whatever config your are using for your platform. That's it!
+Currently, the KUnit Wrapper (``tools/testing/kunit/kunit.py``) (aka
+kunit_tool) only fully supports running tests inside of UML and QEMU; however,
+this is only due to our own time limitations as humans working on KUnit. It is
+entirely possible to support other emulators and even actual hardware, but for
+now QEMU and UML is what is fully supported within the KUnit Wrapper. Again, to
+be clear, this is just the Wrapper. The actualy KUnit tests and the KUnit
+library they are written in is fully architecture agnostic and can be used in
+virtually any setup, you just won't have the benefit of typing a single command
+out of the box and having everything magically work perfectly.
+
+Again, all core KUnit framework features are fully supported on all
+architectures, and using them is straightforward: Most popular architectures
+are supported directly in the KUnit Wrapper via QEMU. Currently, supported
+architectures on QEMU include:
+
+*   i386
+*   x86_64
+*   arm
+*   arm64
+*   alpha
+*   powerpc
+*   riscv
+*   s390
+*   sparc
+
+In order to run KUnit tests on one of these architectures via QEMU with the
+KUnit wrapper, all you need to do is specify the flags ``--arch`` and
+``--cross_compile`` when invoking the KUnit Wrapper. For example, we could run
+the default KUnit tests on ARM in the following manner (assuming we have an ARM
+toolchain installed):
+
+.. code-block:: bash
+
+	tools/testing/kunit/kunit.py run --timeout=60 --jobs=12 --arch=arm --cross_compile=arm-linux-gnueabihf-
+
+Alternatively, if you want to run your tests on real hardware or in some other
+emulation environment, all you need to do is to take your kunitconfig, your
+Kconfig options for the tests you would like to run, and merge them into
+whatever config your are using for your platform. That's it!
 
 For example, let's say you have the following kunitconfig: