[PATCH 1/2] doc: kunit: add information about cleaning source trees

[Shuah Khan <skhan@linuxfoundation.org>]

If kunit run happens in a tree in which a x86_64 kernel was built,
the source tree could be dirty.

"make ARCH=um mrproper" will not clean the x86_64 build artifacts.
Running "make ARCH=x86_64 mrproper" is necessary to clean them.

Add this information to the documentation.

Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
---
 Documentation/dev-tools/kunit/start.rst | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/Documentation/dev-tools/kunit/start.rst b/Documentation/dev-tools/kunit/start.rst
index a98235326bab..568e29aebd6e 100644
--- a/Documentation/dev-tools/kunit/start.rst
+++ b/Documentation/dev-tools/kunit/start.rst
@@ -39,6 +39,18 @@ can run kunit_tool:
 	``make ARCH=um mrproper``, just be aware that this will delete the
 	current configuration and all generated files.
 
+	You may see the following error if a prior build leaves behind
+	header files which 'make ARCH=um mrproper' fails to clean:
+
+	"undefined symbol sev_es_trampoline_start referenced ..."
+
+	This is special case scenario when a prior x86_64 build populates
+	the source tree with arch/x86/realmode/rm/pasyms.h. This header
+	will not be cleaned by 'make ARCH=um mrproper'
+
+	If you encouter this problem, run 'make ARCH=x86_64 mrproper' to
+	remove generated header files.
+
 If everything worked correctly, you should see the following:
 
 .. code-block::
-- 
2.47.2