reproduce (this is a W=1 build):
        git checkout 98f7e32f20d28ec452afb208f9cffc08448a2652
        b4 shazam https://lore.kernel.org/r/20240919-selective-mitigation-v1-2-1846cf41895e@linux.intel.com
        # 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/kernel/cpu/