Hi Dan, FYI, the error/warning still remains. tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master head: 368094df48e680fa51cedb68537408cfa64b788e commit: ec6347bb43395cb92126788a1a5b25302543f815 x86, powerpc: Rename memcpy_mcsafe() to copy_mc_to_{user, kernel}() date: 8 months ago config: x86_64-randconfig-r025-20210610 (attached as .config) compiler: gcc-9 (Debian 9.3.0-22) 9.3.0 reproduce (this is a W=1 build): # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit... git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git git fetch --no-tags linus master git checkout ec6347bb43395cb92126788a1a5b25302543f815 # save the attached .config to linux build tree make W=1 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 >>): 30 | copy_mc_fragile_handle_tail(char *to, char *from, unsigned len) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~ vim +/copy_mc_fragile_handle_tail +30 arch/x86/lib/copy_mc.c 24 25 /* 26 * Similar to copy_user_handle_tail, probe for the write fault point, or 27 * source exception point. 28 */ 29 __visible notrace unsigned long 31 { 32 for (; len; --len, to++, from++) 33 if (copy_mc_fragile(to, from, 1)) 34 break; 35 return len; 36 } 37 #else 38 /* 39 * No point in doing careful copying, or consulting a static key when 40 * there is no #MC handler in the CONFIG_X86_MCE=n case. 41 */ 42 void enable_copy_mc_fragile(void) 43 { 44 } 45 #define copy_mc_fragile_enabled (0) 46 #endif 47 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org