From ae5ba47a990a18c869d66916fd72fb334c45cf91 Mon Sep 17 00:00:00 2001 From: Vince Weaver Date: Wed, 17 Oct 2012 13:03:21 -0400 Subject: [PATCH] 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 Cc: Peter Zijlstra Cc: Paul Mackerras Cc: Arnaldo Carvalho de Melo Cc: eranian@gmail.com Cc: Meadows Lawrence F Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1210171302140.23243@vincent-weaver-1.um.maine.edu Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/perf_event_knc.c | 7 +++---- 1 file 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, -- 2.20.1