reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # https://git.kernel.org/pub/scm/linux/kernel/git/djiang/linux.git/commit/?id=6c38847990ac33ff84ee4c96452cecff09caac37
        git remote add djiang https://git.kernel.org/pub/scm/linux/kernel/git/djiang/linux.git
        git fetch --no-tags djiang cxl/extended-linear
        git checkout 6c38847990ac33ff84ee4c96452cecff09caac37
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=riscv olddefconfig
        ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=riscv SHELL=/bin/bash drivers/cxl/core/