From: Yang Jihong yangjihong1@huawei.com
commit fdbef8c4e68ad423416aa6cc93d1616d6f8ac5b3 upstream.
Commit 3a95200d3f89 ("arm_pmu: Change API to support 64bit counter values") changes the input "value" type from 32-bit to 64-bit, which introduces the following problem: ARMv7 PMU counters is 32-bit width, in big-endian mode, write counter uses high 32-bit, which writes an incorrect value.
Before:
Performance counter stats for 'ls':
2.22 msec task-clock # 0.675 CPUs utilized 0 context-switches # 0.000 K/sec 0 cpu-migrations # 0.000 K/sec 49 page-faults # 0.022 M/sec 2150476593 cycles # 966.663 GHz 2148588788 instructions # 1.00 insn per cycle 2147745484 branches # 965435.074 M/sec 2147508540 branch-misses # 99.99% of all branches
None of the above hw event counters are correct.
Solution:
"value" forcibly converted to 32-bit type before being written to PMU register.
After:
Performance counter stats for 'ls':
2.09 msec task-clock # 0.681 CPUs utilized 0 context-switches # 0.000 K/sec 0 cpu-migrations # 0.000 K/sec 46 page-faults # 0.022 M/sec 2807301 cycles # 1.344 GHz 1060159 instructions # 0.38 insn per cycle 250496 branches # 119.914 M/sec 23192 branch-misses # 9.26% of all branches
Fixes: 3a95200d3f89 ("arm_pmu: Change API to support 64bit counter values") Cc: stable@vger.kernel.org Signed-off-by: Yang Jihong yangjihong1@huawei.com Acked-by: Mark Rutland mark.rutland@arm.com Link: https://lore.kernel.org/r/20210430012659.232110-1-yangjihong1@huawei.com Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/arm/kernel/perf_event_v7.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/arch/arm/kernel/perf_event_v7.c +++ b/arch/arm/kernel/perf_event_v7.c @@ -773,10 +773,10 @@ static inline void armv7pmu_write_counte pr_err("CPU%u writing wrong counter %d\n", smp_processor_id(), idx); } else if (idx == ARMV7_IDX_CYCLE_COUNTER) { - asm volatile("mcr p15, 0, %0, c9, c13, 0" : : "r" (value)); + asm volatile("mcr p15, 0, %0, c9, c13, 0" : : "r" ((u32)value)); } else { armv7_pmnc_select_counter(idx); - asm volatile("mcr p15, 0, %0, c9, c13, 2" : : "r" (value)); + asm volatile("mcr p15, 0, %0, c9, c13, 2" : : "r" ((u32)value)); } }