From 88c9a65e13f393fd60d8b9e9c659a34f9e39967d Mon Sep 17 00:00:00 2001 From: Stephane Eranian Date: Thu, 9 Feb 2012 23:20:56 +0100 Subject: perf/x86: Disable LBR support for older Intel Atom processors The patch adds a restriction for Intel Atom LBR support. Only steppings 10 (PineView) and more recent are supported. Older models do not have a functional LBR. Their LBR does not freeze on PMU interrupt which makes LBR unusable in the context of perf_events. Signed-off-by: Stephane Eranian Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/1328826068-11713-7-git-send-email-eranian@google.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/perf_event_intel_lbr.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c b/arch/x86/kernel/cpu/perf_event_intel_lbr.c index e54a063b2863..07f0ff88e443 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c +++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c @@ -315,6 +315,16 @@ void intel_pmu_lbr_init_snb(void) /* atom */ void intel_pmu_lbr_init_atom(void) { + /* + * only models starting at stepping 10 seems + * to have an operational LBR which can freeze + * on PMU interrupt + */ + if (boot_cpu_data.x86_mask < 10) { + pr_cont("LBR disabled due to erratum"); + return; + } + x86_pmu.lbr_nr = 8; x86_pmu.lbr_tos = MSR_LBR_TOS; x86_pmu.lbr_from = MSR_LBR_CORE_FROM; -- cgit v1.2.1