reproduce:
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # apt-get install sparse
        # sparse version: v0.6.4-66-g0196afe1
        # https://github.com/avpatel/linux/commit/345c59795f11af97ca737e8316ad347f67dc4929
        git remote add avpatel https://github.com/avpatel/linux.git
        git fetch --no-tags avpatel riscv_sbi_nested_v2
        git checkout 345c59795f11af97ca737e8316ad347f67dc4929
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        ~/lkp-tests/kbuild/make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=riscv olddefconfig
        ~/lkp-tests/kbuild/make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=riscv SHELL=/bin/bash drivers/iommu/riscv/