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authorVince Weaver <vincent.weaver@maine.edu>2012-10-17 13:03:21 -0400
committerIngo Molnar <mingo@kernel.org>2012-10-24 12:00:48 +0200
commitae5ba47a990a18c869d66916fd72fb334c45cf91 (patch)
treeca443900763ca1ad5bfd06a2d1017bb3f15be958 /arch
parent032c3851f51141e30de02ed0bc50a7743dfd776d (diff)
perf/x86: Make Intel KNC use full 40-bit width of counters
Early versions of Intel KNC chips have a bug where bits above 32 were not properly set. We worked around this by only using the bottom 32 bits (out of 40 that should be available). It turns out this workaround breaks overflow handling. The buggy silicon will in theory never be used in production systems, so remove this workaround so we get proper overflow support. Signed-off-by: Vince Weaver <vincent.weaver@maine.edu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net> Cc: eranian@gmail.com Cc: Meadows Lawrence F <lawrence.f.meadows@intel.com> Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1210171302140.23243@vincent-weaver-1.um.maine.edu Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/cpu/perf_event_knc.c7
1 files changed, 3 insertions, 4 deletions
diff --git a/arch/x86/kernel/cpu/perf_event_knc.c b/arch/x86/kernel/cpu/perf_event_knc.c
index 7c46bfdbc373..73bcfbdedd50 100644
--- a/arch/x86/kernel/cpu/perf_event_knc.c
+++ b/arch/x86/kernel/cpu/perf_event_knc.c
@@ -226,12 +226,11 @@ static __initconst struct x86_pmu knc_pmu = {
.event_map = knc_pmu_event_map,
.max_events = ARRAY_SIZE(knc_perfmon_event_map),
.apic = 1,
- .max_period = (1ULL << 31) - 1,
+ .max_period = (1ULL << 39) - 1,
.version = 0,
.num_counters = 2,
- /* in theory 40 bits, early silicon is buggy though */
- .cntval_bits = 32,
- .cntval_mask = (1ULL << 32) - 1,
+ .cntval_bits = 40,
+ .cntval_mask = (1ULL << 40) - 1,
.get_event_constraints = x86_get_event_constraints,
.event_constraints = knc_event_constraints,
.format_attrs = intel_knc_formats_attr,