reproduce (this is a W=1 build):
        git checkout 254f49634ee16a731174d2ae34bc50bd5f45e731
        b4 shazam https://lore.kernel.org/r/6-v1-045258567bd6+9fe-ib_uverbs_support_ko_jgg@nvidia.com
        # apt-get install sparse
        # sparse: v0.6.5-rc1

        # 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/infiniband/core/