reproduce:
        # apt-get install sparse
        # sparse version: v0.6.4-66-g0196afe1
        # https://github.com/sean-jc/linux/commit/1a7d10e3e2f52c629b2957b331f206685f11d310
        git remote add sean-jc https://github.com/sean-jc/linux
        git fetch --no-tags sean-jc x86/unfudge_irq_bypass
        git checkout 1a7d10e3e2f52c629b2957b331f206685f11d310
        # 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=i386 olddefconfig
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=i386 SHELL=/bin/bash arch/x86/kvm/