From: Markus Metzger <[email protected]> Starting with Nehalem, the BTS "from" information may in some cases be incorrect (AAJ122).
This has been detected while adding branch tracing support to gdb, where it results in sporadic test fails. Disable BTS support on Nehalem, Westmere, Sandy Bridge, and Ivy Bridge. CC: Mark Kettenis <[email protected]> CC: Pedro Alves <[email protected]> CC: Jan Kratochvil <[email protected]> CC: [email protected] Signed-off-by: Markus Metzger <[email protected]> --- arch/x86/kernel/cpu/perf_event_intel.c | 14 ++++++++++++++ 1 files changed, 14 insertions(+), 0 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c index 6bca492..e72aac9 100644 --- a/arch/x86/kernel/cpu/perf_event_intel.c +++ b/arch/x86/kernel/cpu/perf_event_intel.c @@ -1893,6 +1893,16 @@ static __init void intel_nehalem_quirk(void) } } +static __init void intel_disable_bts(void) +{ + /* + * Erratum AAJ122: LBR, BTM, or BTS records may have incorrect branch + * "from" information afer an EIST transition, T-states, C1E, or + * Adaptive Thermal Throttling. + */ + x86_pmu.bts = 0; +} + __init int intel_pmu_init(void) { union cpuid10_edx edx; @@ -2003,6 +2013,7 @@ __init int intel_pmu_init(void) X86_CONFIG(.event=0xb1, .umask=0x3f, .inv=1, .cmask=1); x86_add_quirk(intel_nehalem_quirk); + intel_disable_bts(); pr_cont("Nehalem events, "); break; @@ -2042,6 +2053,7 @@ __init int intel_pmu_init(void) intel_perfmon_event_map[PERF_COUNT_HW_STALLED_CYCLES_BACKEND] = X86_CONFIG(.event=0xb1, .umask=0x3f, .inv=1, .cmask=1); + intel_disable_bts(); pr_cont("Westmere events, "); break; @@ -2070,6 +2082,7 @@ __init int intel_pmu_init(void) intel_perfmon_event_map[PERF_COUNT_HW_STALLED_CYCLES_BACKEND] = X86_CONFIG(.event=0xb1, .umask=0x01, .inv=1, .cmask=1); + intel_disable_bts(); pr_cont("SandyBridge events, "); break; case 58: /* IvyBridge */ @@ -2092,6 +2105,7 @@ __init int intel_pmu_init(void) intel_perfmon_event_map[PERF_COUNT_HW_STALLED_CYCLES_FRONTEND] = X86_CONFIG(.event=0x0e, .umask=0x01, .inv=1, .cmask=1); + intel_disable_bts(); pr_cont("IvyBridge events, "); break; -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
