From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1192BC433ED for ; Wed, 14 Apr 2021 10:16:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DE2F5613D7 for ; Wed, 14 Apr 2021 10:16:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233095AbhDNKQV (ORCPT ); Wed, 14 Apr 2021 06:16:21 -0400 Received: from foss.arm.com ([217.140.110.172]:54358 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232032AbhDNKQT (ORCPT ); Wed, 14 Apr 2021 06:16:19 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 8E88611B3; Wed, 14 Apr 2021 03:15:58 -0700 (PDT) Received: from [192.168.0.110] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 91D153F73B; Wed, 14 Apr 2021 03:15:57 -0700 (PDT) Subject: Re: arch/arm64/kvm/perf.c:58:36: error: implicit declaration of function 'perf_num_counters' To: Nathan Chancellor , kernel test robot Cc: Marc Zyngier , kbuild-all@lists.01.org, clang-built-linux@googlegroups.com, linux-kernel@vger.kernel.org, Paolo Bonzini References: <202103262006.nHFq086E-lkp@intel.com> <20210413200057.ankb4e26ytgal7ev@archlinux-ax161> From: Alexandru Elisei Message-ID: <9bdf177a-8fe2-effc-be88-3b65fe175292@arm.com> Date: Wed, 14 Apr 2021 11:16:30 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.9.0 MIME-Version: 1.0 In-Reply-To: <20210413200057.ankb4e26ytgal7ev@archlinux-ax161> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 >> >> 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-all@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