tree: https://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux.git hyperv-next head: 0d9f8d427756841b79df5da8bed98dc113299637 commit: 325d7a85e1ea52c5ca82b246c332e08939b085df [3/5] Drivers: hv: Make portions of Hyper-V init code be arch neutral config: x86_64-randconfig-c002-20210713 (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/hyperv/linux.git/commit/?... git remote add hyperv-linux https://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux.git git fetch --no-tags hyperv-linux hyperv-next git checkout 325d7a85e1ea52c5ca82b246c332e08939b085df # save the attached .config to linux build tree mkdir build_dir make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All errors (new ones prefixed by >>): ld: arch/x86/kernel/cpu/mshyperv.o: in function `ms_hyperv_init_platform': mshyperv.c:(.init.text+0x130): undefined reference to `ms_hyperv' ld: mshyperv.c:(.init.text+0x147): undefined reference to `ms_hyperv' ld: mshyperv.c:(.init.text+0x153): undefined reference to `ms_hyperv' ld: mshyperv.c:(.init.text+0x15e): undefined reference to `ms_hyperv' ld: mshyperv.c:(.init.text+0x16c): undefined reference to `ms_hyperv' ld: arch/x86/kernel/cpu/mshyperv.o:mshyperv.c:(.init.text+0x17b): more undefined references to `ms_hyperv' follow ld: arch/x86/kernel/cpu/mshyperv.o: in function `ms_hyperv_init_platform': mshyperv.c:(.init.text+0x25d): undefined reference to `hv_root_partition' ld: mshyperv.c:(.init.text+0x2d6): undefined reference to `ms_hyperv' ld: mshyperv.c:(.init.text+0x2e1): undefined reference to `ms_hyperv' ld: mshyperv.c:(.init.text+0x2eb): undefined reference to `ms_hyperv' ld: mshyperv.c:(.init.text+0x2f6): undefined reference to `ms_hyperv' ld: mshyperv.c:(.init.text+0x32e): undefined reference to `ms_hyperv' ld: arch/x86/kernel/cpu/mshyperv.o:mshyperv.c:(.init.text+0x339): more undefined references to `ms_hyperv' follow --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org