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Subject[PATCH 4/5] perf, x86: Clear the LBRs on init
Some CPUs have errata where the LBR is not cleared on Power-On. So
always clear the LBRs before use.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
arch/x86/kernel/cpu/perf_event_intel.c | 18 ++++++++++++++++--
arch/x86/kernel/cpu/perf_event_intel_lbr.c | 3 +++
2 files changed, 19 insertions(+), 2 deletions(-)
Index: linux-2.6/arch/x86/kernel/cpu/perf_event_intel.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/perf_event_intel.c
+++ linux-2.6/arch/x86/kernel/cpu/perf_event_intel.c
@@ -775,6 +775,20 @@ static __initconst struct x86_pmu core_p
.event_constraints = intel_core_event_constraints,
};

+static void intel_pmu_cpu_starting(int cpu)
+{
+ init_debug_store_on_cpu(cpu);
+ /*
+ * Deal with CPUs that don't clear their LBRs on power-up.
+ */
+ intel_pmu_lbr_reset();
+}
+
+static void intel_pmu_cpu_dying(int cpu)
+{
+ fini_debug_store_on_cpu(cpu);
+}
+
static __initconst struct x86_pmu intel_pmu = {
.name = "Intel",
.handle_irq = intel_pmu_handle_irq,
@@ -796,8 +810,8 @@ static __initconst struct x86_pmu intel_
.max_period = (1ULL << 31) - 1,
.get_event_constraints = intel_get_event_constraints,

- .cpu_starting = init_debug_store_on_cpu,
- .cpu_dying = fini_debug_store_on_cpu,
+ .cpu_starting = intel_pmu_cpu_starting,
+ .cpu_dying = intel_pmu_cpu_dying,
};

static void intel_clowertown_quirks(void)
Index: linux-2.6/arch/x86/kernel/cpu/perf_event_intel_lbr.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/perf_event_intel_lbr.c
+++ linux-2.6/arch/x86/kernel/cpu/perf_event_intel_lbr.c
@@ -53,6 +53,9 @@ static void intel_pmu_lbr_reset_64(void)

static void intel_pmu_lbr_reset(void)
{
+ if (!x86_pmu.lbr_nr)
+ return;
+
if (x86_pmu.intel_cap.lbr_format == LBR_FORMAT_32)
intel_pmu_lbr_reset_32();
else
--



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