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 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
