reproduce:
        # apt-get install sparse
        # sparse version: v0.6.4-66-g0196afe1
        git remote add vivek-drm-tip https://gitlab.freedesktop.org/Vivek/drm-tip.git
        git fetch --no-tags vivek-drm-tip vfio_dmabuf_v1
        git checkout 5ef225e951f7d39f11703af6060984e434c6dc4b
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=x86_64 olddefconfig
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=x86_64 SHELL=/bin/bash drivers/vfio/pci/