tree: https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git kvm/protected-memory head: d9455e6eabef4b9be5f33c418a8046e0389edade commit: 5a774560c2b22a5e2ce3f0b0089c07312204e0c5 [4/16] x86/kvm: Use bounce buffers for KVM memory protection config: x86_64-randconfig-a014-20200916 (attached as .config) compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project 9e3842d60351f986d77dfe0a94f76e4fd895f188) reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # install x86_64 cross compiling tool for clang build # apt-get install binutils-x86-64-linux-gnu git checkout 5a774560c2b22a5e2ce3f0b0089c07312204e0c5 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): arch/x86/mm/mem_encrypt_common.c:16:6: warning: no previous prototype for function 'force_dma_unencrypted' [-Wmissing-prototypes] bool force_dma_unencrypted(struct device *dev) ^ arch/x86/mm/mem_encrypt_common.c:16:1: note: declare 'static' if the function is not intended to be used outside of this translation unit bool force_dma_unencrypted(struct device *dev) ^ static void __init mem_encrypt_init(void) ^ arch/x86/mm/mem_encrypt_common.c:41:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void __init mem_encrypt_init(void) ^ static 2 warnings generated. # https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/com... git remote add arm-platforms https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git git fetch --no-tags arm-platforms kvm/protected-memory git checkout 5a774560c2b22a5e2ce3f0b0089c07312204e0c5 vim +/mem_encrypt_init +41 arch/x86/mm/mem_encrypt_common.c 40 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org