reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # https://github.com/alexshi/linux/commit/a158e7e787b56bc7f1b4bb582a0e8ec65cacec4b
        git remote add alexshi https://github.com/alexshi/linux.git
        git fetch --no-tags alexshi mmunstable
        git checkout a158e7e787b56bc7f1b4bb582a0e8ec65cacec4b
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-14.1.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-14.1.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash arch/s390/mm/