tree: https://github.com/weiny2/linux-kernel.git lm-misc head: 8c385a87dc5cb4d98fa417d3dd9481f3fbe4c625 commit: 9bbedda97f815fb2b6478966706968af63c983c2 [7/8] arch/kmap_atomic: Consolidate duplicate code config: i386-allnoconfig (attached as .config) compiler: gcc-7 (Ubuntu 7.5.0-6ubuntu2) 7.5.0 reproduce: git checkout 9bbedda97f815fb2b6478966706968af63c983c2 # save the attached .config to linux build tree make ARCH=i386 If you fix the issue, kindly add following tag as appropriate Reported-by: kbuild test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): In file included from arch/x86/mm/highmem_32.c:2:0: include/linux/highmem.h: In function 'kmap': include/linux/highmem.h:40:9: error: implicit declaration of function '__kmap'; did you mean 'kmap'? [-Werror=implicit-function-declaration] return __kmap(page); ^~~~~~ kmap include/linux/highmem.h:40:9: warning: return makes pointer from integer without a cast [-Wint-conversion] return __kmap(page); ^~~~~~~~~~~~ include/linux/highmem.h: In function 'kunmap': include/linux/highmem.h:48:3: warning: 'return' with no value, in function returning non-void [-Wreturn-type] return; ^~~~~~ include/linux/highmem.h:44:21: note: declared here static inline void *kunmap(struct page *page) ^~~~~~ arch/x86/mm/highmem_32.c: In function 'kmap_atomic_prot': unsigned long vaddr = __kmap_atomic(page); ^~~~~~~~~~~~~ cc1: some warnings being treated as errors vim +17 arch/x86/mm/highmem_32.c 6 7 /* 8 * kmap_atomic/kunmap_atomic is significantly faster than kmap/kunmap because 9 * no global lock is needed and because the kmap code must perform a global TLB 10 * invalidation when the kmap pool wraps. 11 * 12 * However when holding an atomic kmap it is not legal to sleep, so atomic 13 * kmaps are appropriate for short, tight code paths only. 14 */ 15 void *kmap_atomic_prot(struct page *page, pgprot_t prot) 16 { 18 int idx, type; 19 20 if (vaddr) 21 return (void *)vaddr; 22 23 type = kmap_atomic_idx_push(); 24 idx = type + KM_TYPE_NR*smp_processor_id(); 25 vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx); 26 BUG_ON(!pte_none(*(kmap_pte-idx))); 27 set_pte(kmap_pte-idx, mk_pte(page, prot)); 28 arch_flush_lazy_mmu_mode(); 29 30 return (void *)vaddr; 31 } 32 EXPORT_SYMBOL(kmap_atomic_prot); 33 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org