reproduce:
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # apt-get install sparse
        # sparse version: v0.6.4-61-g09411a7a-dirty
        # https://github.com/jcmvbkbc/linux-xtensa/commit/1d4c0e9d617182a90eb506db56bff1b70f01c2ed
        git remote add jcmvbkbc-xtensa https://github.com/jcmvbkbc/linux-xtensa
        git fetch --no-tags jcmvbkbc-xtensa xtensa-6.8-rc2-esp32
        git checkout 1d4c0e9d617182a90eb506db56bff1b70f01c2ed
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        ~/lkp-tests/kbuild/make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=s390 olddefconfig
        ~/lkp-tests/kbuild/make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=s390 SHELL=/bin/bash drivers/misc/ mm/