reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git/commit/?id=5990078704982cce2dc9a952fb328771a7e7d991
        git remote add rppt https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git
        git fetch --no-tags rppt direct-map/v0
        git checkout 5990078704982cce2dc9a952fb328771a7e7d991

        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=x86_64 olddefconfig
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash kernel/