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authorStephane Eranian <eranian@google.com>2012-02-09 23:20:56 +0100
committerIngo Molnar <mingo@elte.hu>2012-03-05 14:55:41 +0100
commit88c9a65e13f393fd60d8b9e9c659a34f9e39967d (patch)
treea609acb6ae06c162015d6d32b9c8a1d5313ec3e2
parentc5cc2cd906ea9fe73e3c93f9ad824996faa278cc (diff)
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 <eranian@google.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1328826068-11713-7-git-send-email-eranian@google.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--arch/x86/kernel/cpu/perf_event_intel_lbr.c10
1 files changed, 10 insertions, 0 deletions
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;