tree: https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git kvm-arm64/mmu/guest-MMIO-guard head: 63d0c848f6eeb82c8abbdc836c6c71a1c907a5cd commit: 63d0c848f6eeb82c8abbdc836c6c71a1c907a5cd [18/18] guest hacks config: um-x86_64_defconfig (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/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-arm64/mmu/guest-MMIO-guard git checkout 63d0c848f6eeb82c8abbdc836c6c71a1c907a5cd # save the attached .config to linux build tree make W=1 ARCH=um SUBARCH=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 >>): 31 | void __weak ioremap_page_range_hook(unsigned long addr, unsigned long end, | ^~~~~~~~~~~~~~~~~~~~~~~ vim +/ioremap_page_range_hook +31 mm/ioremap.c 30 32 phys_addr_t phys_addr, pgprot_t prot) 33 { 34 } 35 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org