reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/ardb/linux.git/commit/?id=83f306426e8464e9a9d0734d96b6e23b80d1fb2b
        git remote add ardb git://git.kernel.org/pub/scm/linux/kernel/git/ardb/linux.git
        git fetch --no-tags ardb x86-pie-for-sev-v2a
        git checkout 83f306426e8464e9a9d0734d96b6e23b80d1fb2b
        # 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 arch/x86/kernel/ arch/x86/mm/