Hi, On 4/13/21 9:00 PM, Nathan Chancellor wrote: > On Fri, Mar 26, 2021 at 08:27:13PM +0800, kernel test robot wrote: >> Hi Marc, >> >> FYI, the error/warning still remains. >> >> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git >> master >> head: db24726bfefa68c606947a86132591568a06bfb4 >> commit: 6b5b368fccd7109b052e45af8ba1464c8d140a49 KVM: arm64: Turn >> kvm_arm_support_pmu_v3() into a static key >> date: 3 weeks ago >> config: arm64-randconfig-r005-20210326 (attached as .config) >> compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project >> f490a5969bd52c8a48586f134ff8f02ccbb295b3) >> 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 arm64 cross compiling tool for clang build >> # apt-get install binutils-aarch64-linux-gnu >> # >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6b5b368fccd7109b052e45af8ba1464c8d140a49 >> git remote add linus >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git >> git fetch --no-tags linus master >> git checkout 6b5b368fccd7109b052e45af8ba1464c8d140a49 >> # save the attached .config to linux build tree >> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross >> ARCH=arm64 >> >> If you fix the issue, kindly add following tag as appropriate >> Reported-by: kernel test robot <l...@intel.com> >> >> All errors (new ones prefixed by >>): >> >>>> arch/arm64/kvm/perf.c:58:36: error: implicit declaration of function >>>> 'perf_num_counters' [-Werror,-Wimplicit-function-declaration] >> if (IS_ENABLED(CONFIG_ARM_PMU) && perf_num_counters() > 0) >> ^ >> 1 error generated. >> >> >> vim +/perf_num_counters +58 arch/arm64/kvm/perf.c >> >> 50 >> 51 int kvm_perf_init(void) >> 52 { >> 53 /* >> 54 * Check if HW_PERF_EVENTS are supported by checking >> the number of >> 55 * hardware performance counters. This could ensure the >> presence of >> 56 * a physical PMU and CONFIG_PERF_EVENT is selected. >> 57 */ >> > 58 if (IS_ENABLED(CONFIG_ARM_PMU) && perf_num_counters() > >> 0) >> 59 static_branch_enable(&kvm_arm_pmu_available); >> 60 >> 61 return >> perf_register_guest_info_callbacks(&kvm_guest_cbs); >> 62 } >> 63 >> >> --- >> 0-DAY CI Kernel Test Service, Intel Corporation >> https://lists.01.org/hyperkitty/list/kbuild-...@lists.01.org > I just ran into this again. It is not a clang specific issue, it > reproduces quite easily with arm64 defconfig minus CONFIG_PERF_EVENTS > and gcc 10.3.0: > > arch/arm64/kvm/perf.c: In function 'kvm_perf_init': > arch/arm64/kvm/perf.c:58:36: error: implicit declaration of function > 'perf_num_counters'; did you mean 'dec_mm_counter'? > [-Werror=implicit-function-declaration] > 58 | if (IS_ENABLED(CONFIG_ARM_PMU) && perf_num_counters() > 0) > | ^~~~~~~~~~~~~~~~~ > | dec_mm_counter > cc1: some warnings being treated as errors
I was also able to reproduce it with gcc 10.2.0. I think the problem is that the perf_num_counters() declaration is guarded by CONFIG_PERF_EVENTS (in include/linux/perf_event.h), the implementation is in drivers/perf/arm_pmu.c, which depends on CONFIG_ARM_PMU, but CONFIG_ARM_PMU=y doesn't select CONFIG_PERF_EVENTS. So we end up in a situation where we have the implementation of perf_num_counters(), but no prototype (CONFIG_ARM_PMU=y, CONFIG_PERF_EVENTS is not set). Thanks, Alex > > I am not sure what the cleanest solution would be for providing a static > inline version of perf_num_counters() would be, as only arm64 actually > uses it (sh and s390 define it but it does not appear to be used) but it > is only available through CONFIG_ARM_PMU instead of just > CONFIG_PERF_EVENTS like the other two architectures mentioned above. > > Cheers, > Nathan
