From 425507fa5f321bb5ce1b5eb57a9586e0cf0b9802 Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Sun, 10 May 2015 12:22:46 -0700 Subject: [PATCH] perf/x86/intel/lbr: Optimize v4 LBR unfreezing In Arch perfmon v4 the GLOBAL_STATUS reset automatically unfreezes LBRs. So no need to do it manually in the LBR code. Add a check to skip it. v2: Move test up to beginning of function. Signed-off-by: Andi Kleen Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: eranian@google.com Link: http://lkml.kernel.org/r/1431285767-27027-9-git-send-email-andi@firstfloor.org Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/perf_event_intel_lbr.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c b/arch/x86/kernel/cpu/perf_event_intel_lbr.c index 2fb57373beca..769a42f874dc 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c +++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c @@ -140,6 +140,13 @@ static void __intel_pmu_lbr_enable(bool pmi) struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events); u64 debugctl, lbr_select = 0, orig_debugctl; + /* + * No need to unfreeze manually, as v4 can do that as part + * of the GLOBAL_STATUS ack. + */ + if (pmi && x86_pmu.version >= 4) + return; + /* * No need to reprogram LBR_SELECT in a PMI, as it * did not change.