reproduce (this is a W=1 build):
        # https://github.com/sean-jc/linux/commit/b2746b169a9de85ccd1760906aadedd71e30497d
        git remote add sean-jc https://github.com/sean-jc/linux
        git fetch --no-tags sean-jc x86/fastpath_pi_nv
        git checkout b2746b169a9de85ccd1760906aadedd71e30497d
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=i386 olddefconfig
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash arch/x86/kvm/