reproduce:
        # https://git.kernel.org/pub/scm/linux/kernel/git/sashal/linux.git/commit/?id=340fcb4bf8938a649242cde84aa7bafe17dd5325
        git remote add sashal https://git.kernel.org/pub/scm/linux/kernel/git/sashal/linux.git
        git fetch --no-tags sashal dedup-lsb128
        git checkout 340fcb4bf8938a649242cde84aa7bafe17dd5325
        make menuconfig
        # enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
        # pip install -r Documentation/sphinx/requirements.txt
        make htmldocs