From 3c413cfdf8ac1b63b5cc9af2d2c69b5b0973579f Mon Sep 17 00:00:00 2001 From: Yang Jihong Date: Fri, 30 Apr 2021 09:26:59 +0800 Subject: [PATCH] arm_pmu: Fix write counter incorrect in ARMv7 big-endian mode BugLink: https://bugs.launchpad.net/bugs/1938340 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: Signed-off-by: Yang Jihong Acked-by: Mark Rutland Link: https://lore.kernel.org/r/20210430012659.232110-1-yangjihong1@huawei.com Signed-off-by: Will Deacon Signed-off-by: Greg Kroah-Hartman Signed-off-by: Kamal Mostafa Signed-off-by: Stefan Bader --- arch/arm/kernel/perf_event_v7.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/arm/kernel/perf_event_v7.c b/arch/arm/kernel/perf_event_v7.c index 2924d7910b10..eb2190477da1 100644 --- 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_counter(struct perf_event *event, u64 value) 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)); } } -- 2.39.5