Re: [PATCH V8 5/6] arm64/perf: Add branch stack support in ARMV8 PMU

[Anshuman Khandual <anshuman.khandual@arm.com>]

On 2/3/23 17:01, Will Deacon wrote:
> On Tue, Jan 31, 2023 at 12:28:17AM +0800, kernel test robot wrote:
>> Hi Anshuman,
>>
>> Thank you for the patch! Perhaps something to improve:
>>
>> [auto build test WARNING on arm64/for-next/core]
>> [also build test WARNING on tip/perf/core acme/perf/core linus/master v6.2-rc6 next-20230130]
>> [If your patch is applied to the wrong git tree, kindly drop us a note.
>> And when submitting patch, we suggest to use '--base' as documented in
>> https://git-scm.com/docs/git-format-patch#_base_tree_information]
>>
>> url:    https://github.com/intel-lab-lkp/linux/commits/Anshuman-Khandual/drivers-perf-arm_pmu-Add-new-sched_task-callback/20230123-210254
>> base:   https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-next/core
>> patch link:    https://lore.kernel.org/r/20230123125956.1350336-6-anshuman.khandual%40arm.com
>> patch subject: [PATCH V8 5/6] arm64/perf: Add branch stack support in ARMV8 PMU
>> config: arm64-randconfig-r016-20230130 (https://download.01.org/0day-ci/archive/20230131/202301310047.b5iv9hM8-lkp@intel.com/config)
>> compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project 4196ca3278f78c6e19246e54ab0ecb364e37d66a)
>> 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://github.com/intel-lab-lkp/linux/commit/0deba04ac45f8632b8579cb5cbf908b9f4428402
>>         git remote add linux-review https://github.com/intel-lab-lkp/linux
>>         git fetch --no-tags linux-review Anshuman-Khandual/drivers-perf-arm_pmu-Add-new-sched_task-callback/20230123-210254
>>         git checkout 0deba04ac45f8632b8579cb5cbf908b9f4428402
>>         # save the config file
>>         mkdir build_dir && cp config build_dir/.config
>>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm64 olddefconfig
>>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm64 prepare
>>
>> If you fix the issue, kindly add following tag where applicable
>> | Reported-by: kernel test robot <lkp@intel.com>
>>
>> All warnings (new ones prefixed by >>):
>>
>>    In file included from arch/arm64/kernel/asm-offsets.c:15:
>>    In file included from include/linux/kvm_host.h:45:
>>    In file included from arch/arm64/include/asm/kvm_host.h:36:
>>    In file included from include/kvm/arm_pmu.h:11:
>>>> arch/arm64/include/asm/perf_event.h:280:20: warning: function 'has_branch_stack' has internal linkage but is not defined [-Wundefined-internal]
>>    static inline bool has_branch_stack(struct perf_event *event);
>>                       ^
>>    arch/arm64/include/asm/perf_event.h:284:16: note: used here
>>            WARN_ON_ONCE(!has_branch_stack(event));
>>                          ^
>>    1 warning generated.
>> --
>>    In file included from arch/arm64/kernel/asm-offsets.c:15:
>>    In file included from include/linux/kvm_host.h:45:
>>    In file included from arch/arm64/include/asm/kvm_host.h:36:
>>    In file included from include/kvm/arm_pmu.h:11:
>>>> arch/arm64/include/asm/perf_event.h:280:20: warning: function 'has_branch_stack' has internal linkage but is not defined [-Wundefined-internal]
>>    static inline bool has_branch_stack(struct perf_event *event);
>>                       ^
>>    arch/arm64/include/asm/perf_event.h:284:16: note: used here
>>            WARN_ON_ONCE(!has_branch_stack(event));
>>                          ^
>>    1 warning generated.
> 
> This looks like it should be fixed. I'd also like to see Mark's ack on the

This build warning is triggered when CONFIG_PERF_EVENTS is not enabled, when
all the fallback stubs in there try to use has_branch_stack() which does not
get defined. The following change, fixes the problem.

diff --git a/arch/arm64/include/asm/perf_event.h b/arch/arm64/include/asm/perf_event.h
index 97db96326e13..1f68c125eb1a 100644
--- a/arch/arm64/include/asm/perf_event.h
+++ b/arch/arm64/include/asm/perf_event.h
@@ -277,8 +277,6 @@ struct pmu_hw_events;
 struct arm_pmu;
 struct perf_event;
 
-static inline bool has_branch_stack(struct perf_event *event);
-
 #ifdef CONFIG_ARM64_BRBE
 void armv8pmu_branch_read(struct pmu_hw_events *cpuc, struct perf_event *event);
 bool armv8pmu_branch_valid(struct perf_event *event);
@@ -289,6 +287,9 @@ void armv8pmu_branch_reset(void);
 int armv8pmu_private_alloc(struct arm_pmu *arm_pmu);
 void armv8pmu_private_free(struct arm_pmu *arm_pmu);
 #else
+#ifdef CONFIG_PERF_EVENTS
+static inline bool has_branch_stack(struct perf_event *event);
+
 static inline void armv8pmu_branch_read(struct pmu_hw_events *cpuc, struct perf_event *event)
 {
        WARN_ON_ONCE(!has_branch_stack(event));
@@ -316,3 +317,4 @@ static inline int armv8pmu_private_alloc(struct arm_pmu *arm_pmu) { return 0; }
 static inline void armv8pmu_private_free(struct arm_pmu *arm_pmu) { }
 #endif
 #endif
+#endif

> final series, since he had some detailed comments on the previous version.
> 
> Will