tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master head: 92477dd1faa650e50bd3bb35a6c0b8d09198cc35 commit: 501444905fcb4166589fda99497c273ac5efc65e x86/centaur: Use common IA32_FEAT_CTL MSR initialization date: 1 year, 9 months ago config: i386-randconfig-r036-20210927 (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/?id=501444905fcb4166589fda99497c273ac5efc65e git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git git fetch --no-tags linus master git checkout 501444905fcb4166589fda99497c273ac5efc65e # save the attached .config to linux build tree make W=1 ARCH=i386 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot All warnings (new ones prefixed by >>): >> arch/x86/kernel/cpu/feat_ctl.c:8:6: warning: no previous prototype for 'init_ia32_feat_ctl' [-Wmissing-prototypes] 8 | void init_ia32_feat_ctl(struct cpuinfo_x86 *c) | ^~~~~~~~~~~~~~~~~~ vim +/init_ia32_feat_ctl +8 arch/x86/kernel/cpu/feat_ctl.c 1db2a6e1e29ff994 Sean Christopherson 2019-12-20 7 1db2a6e1e29ff994 Sean Christopherson 2019-12-20 @8 void init_ia32_feat_ctl(struct cpuinfo_x86 *c) :::::: The code at line 8 was first introduced by commit :::::: 1db2a6e1e29ff994443a9eef7cf3d26104c777a7 x86/intel: Initialize IA32_FEAT_CTL MSR at boot :::::: TO: Sean Christopherson :::::: CC: Borislav Petkov --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org