Messages in this thread Patch in this message | | | From | kan.liang@linux ... | Subject | [PATCH] perf/x86/intel: Fix: Use u64 for limit_period | Date | Thu, 1 Mar 2018 12:54:54 -0500 |
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From: Kan Liang <kan.liang@linux.intel.com>
The large fixed period could be truncated on Broadwell. For example, perf record -e cycles -c 10000000000. The fixed period is 0x2540BE400. But the period which finally applied is 0x540BE400.
Because the limit_period is unsigned, which is 32bit. The higher 32bit of the period will be truncated.
The issue is introduced since 'commit 294fe0f52a44 ("perf/x86/intel: Add INST_RETIRED.ALL workarounds")
Although the 'left' is s64, the value of 'left' must be positive when calling limit_period. bdw_limit_period() only modify the lowest 6 bits. It doesn't touch the higher 32bit. So it's safe to use u64 to replace the unsigned.
Fixes: 294fe0f52a44 ("perf/x86/intel: Add INST_RETIRED.ALL workarounds") Signed-off-by: Kan Liang <kan.liang@linux.intel.com> --- arch/x86/events/intel/core.c | 2 +- arch/x86/events/perf_event.h | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c index 916b6e6..8e722e4 100644 --- a/arch/x86/events/intel/core.c +++ b/arch/x86/events/intel/core.c @@ -3222,7 +3222,7 @@ glp_get_event_constraints(struct cpu_hw_events *cpuc, int idx, * Therefore the effective (average) period matches the requested period, * despite coarser hardware granularity. */ -static unsigned bdw_limit_period(struct perf_event *event, unsigned left) +static u64 bdw_limit_period(struct perf_event *event, u64 left) { if ((event->hw.config & INTEL_ARCH_EVENT_MASK) == X86_CONFIG(.event=0xc0, .umask=0x01)) { diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h index b5352f1..810013d 100644 --- a/arch/x86/events/perf_event.h +++ b/arch/x86/events/perf_event.h @@ -561,7 +561,7 @@ struct x86_pmu { struct x86_pmu_quirk *quirks; int perfctr_second_write; bool late_ack; - unsigned (*limit_period)(struct perf_event *event, unsigned l); + u64 (*limit_period)(struct perf_event *event, u64 l); /* * sysfs attrs -- 2.4.11
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