tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git x86/entry head: da0d0553b69e8159a4f25f7981d752e20c22f2ab commit: 096b735813d5fef5b6b0e80e7585fba57c55e05b [93/119] x86/entry: Switch XEN/PV hypercall entry to IDTENTRY config: x86_64-allyesconfig (attached as .config) compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project 3393cc4cebf9969db94dc424b7a2b6195589c33b) 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 096b735813d5fef5b6b0e80e7585fba57c55e05b # 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: kbuild test robot <lkp(a)intel.com&gt; All error/warnings (new ones prefixed by >>, old ones prefixed by <<): arch/x86/entry/common.c:272:24: warning: no previous prototype for function 'prepare_exit_to_usermode' [-Wmissing-prototypes] __visible noinstr void prepare_exit_to_usermode(struct pt_regs *regs) ^ arch/x86/entry/common.c:272:19: note: declare 'static' if the function is not intended to be used outside of this translation unit __visible noinstr void prepare_exit_to_usermode(struct pt_regs *regs) ^ static arch/x86/entry/common.c:334:24: warning: no previous prototype for function 'syscall_return_slowpath' [-Wmissing-prototypes] __visible noinstr void syscall_return_slowpath(struct pt_regs *regs) ^ arch/x86/entry/common.c:334:19: note: declare 'static' if the function is not intended to be used outside of this translation unit __visible noinstr void syscall_return_slowpath(struct pt_regs *regs) ^ static boot inhcall = __this_cpu_read(xen_in_preemptible_hcall); ^~~~ bool include/linux/types.h:30:17: note: 'bool' declared here typedef _Bool bool; ^ __visible noinstr void xen_pv_evtchn_do_upcall(struct pt_regs *regs) ^ arch/x86/entry/common.c:731:19: note: declare 'static' if the function is not intended to be used outside of this translation unit __visible noinstr void xen_pv_evtchn_do_upcall(struct pt_regs *regs) ^ static 3 warnings and 1 error generated. vim +707 arch/x86/entry/common.c 700 701 /* 702 * In case of scheduling the flag must be cleared and restored after 703 * returning from schedule as the task might move to a different CPU. 704 */ 705 static __always_inline bool get_and_clear_inhcall(void) 706 { 708 709 __this_cpu_write(xen_in_preemptible_hcall, false); 710 } 711 712 static __always_inline void restore_inhcall(bool inhcall) 713 { 714 __this_cpu_write(xen_in_preemptible_hcall, inhcall); 715 } 716 #else 717 static __always_inline bool get_and_clear_inhcall(void) { return false; } 718 static __always_inline void restore_inhcall(bool inhcall) { } 719 #endif 720 721 static void __xen_pv_evtchn_do_upcall(void) 722 { 723 irq_enter_rcu(); 724 inc_irq_stat(irq_hv_callback_count); 725 726 xen_hvm_evtchn_do_upcall(); 727 728 irq_exit_rcu(); 729 } 730 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org