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-s021-20200916 (attached as .config) compiler: gcc-9 (Debian 9.3.0-15) 9.3.0 reproduce: # apt-get install sparse # sparse version: v0.6.2-201-g24bdaac6-dirty git checkout 5a774560c2b22a5e2ce3f0b0089c07312204e0c5 # save the attached .config to linux build tree make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' 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 'force_dma_unencrypted' [-Wmissing-prototypes] 16 | bool force_dma_unencrypted(struct device *dev) | ^~~~~~~~~~~~~~~~~~~~~ 41 | void __init mem_encrypt_init(void) | ^~~~~~~~~~~~~~~~ # 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