+ struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
+ static const unsigned long nhm_magic[4] = {
+ 0x4300B5,
+ 0x4300D2,
+ 0x4300B1,
+ 0x4300B1
+ };
+ struct perf_event *event;
+ int i;
+
+ /*
+ * The Errata requires below steps:
+ * 1) Clear MSR_IA32_PEBS_ENABLE and MSR_CORE_PERF_GLOBAL_CTRL;
+ * 2) Configure 4 PERFEVTSELx with the magic events and clear
+ * the corresponding PMCx;
+ * 3) set bit0~bit3 of MSR_CORE_PERF_GLOBAL_CTRL;
+ * 4) Clear MSR_CORE_PERF_GLOBAL_CTRL;
+ * 5) Clear 4 pairs of ERFEVTSELx and PMCx;
+ */
+
+ /*
+ * The real steps we choose are a little different from above.
+ * A) To reduce MSR operations, we don't run step 1) as they
+ * are already cleared before this function is called;
+ * B) Call x86_perf_event_update to save PMCx before configuring
+ * PERFEVTSELx with magic number;
+ * C) With step 5), we do clear only when the PERFEVTSELx is
+ * not used currently.
+ * D) Call x86_perf_event_set_period to restore PMCx;
+ */