4.16-stable review patch. If anyone has any objections, please let me know.
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From: Kan Liang kan.liang@linux.intel.com
[ Upstream commit f605cfca8c39ffa2b98c06d2b9f30ba64f1e54e3 ]
Large fixed period values could be truncated on Broadwell, for example:
perf record -e cycles -c 10000000000
Here the fixed period is 0x2540BE400, but the period which finally applied is 0x540BE400 - which is wrong.
The reason is that x86_pmu::limit_period() uses an u32 parameter, so the high 32 bits of 'period' get truncated.
This bug was introduced in:
commit 294fe0f52a44 ("perf/x86/intel: Add INST_RETIRED.ALL workarounds")
It's safe to use u64 instead of u32:
- Although the 'left' is s64, the value of 'left' must be positive when calling limit_period().
- bdw_limit_period() only modifies the lowest 6 bits, it doesn't touch the higher 32 bits.
Signed-off-by: Kan Liang kan.liang@linux.intel.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Cc: Alexander Shishkin alexander.shishkin@linux.intel.com Cc: Arnaldo Carvalho de Melo acme@redhat.com Cc: Jiri Olsa jolsa@redhat.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Stephane Eranian eranian@google.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Vince Weaver vincent.weaver@maine.edu Fixes: 294fe0f52a44 ("perf/x86/intel: Add INST_RETIRED.ALL workarounds") Link: http://lkml.kernel.org/r/1519926894-3520-1-git-send-email-kan.liang@linux.in... [ Rewrote unacceptably bad changelog. ] Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/events/intel/core.c | 2 +- arch/x86/events/perf_event.h | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)
--- a/arch/x86/events/intel/core.c +++ b/arch/x86/events/intel/core.c @@ -3196,7 +3196,7 @@ glp_get_event_constraints(struct cpu_hw_ * 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)) { --- a/arch/x86/events/perf_event.h +++ b/arch/x86/events/perf_event.h @@ -557,7 +557,7 @@ 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