From: Vince Weaver Date: Wed, 17 Oct 2012 17:03:21 +0000 (-0400) Subject: perf/x86: Make Intel KNC use full 40-bit width of counters X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=ae5ba47a990a18c869d66916fd72fb334c45cf91;p=linux.git 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 --- diff --git a/arch/x86/kernel/cpu/perf_event_knc.c b/arch/x86/kernel/cpu/perf_event_knc.c index 7c46bfdbc3732..73bcfbdedd50a 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,