oprofile: Implement performance counter multiplexing

The number of hardware counters is limited. The multiplexing feature
enables OProfile to gather more events than counters are provided by
the hardware. This is realized by switching between events at an user
specified time interval.

A new file (/dev/oprofile/time_slice) is added for the user to specify
the timer interval in ms. If the number of events to profile is higher
than the number of hardware counters available, the patch will
schedule a work queue that switches the event counter and re-writes
the different sets of values into it. The switching mechanism needs to
be implemented for each architecture to support multiplexing. This
patch only implements AMD CPU support, but multiplexing can be easily
extended for other models and architectures.

There are follow-on patches that rework parts of this patch.

Signed-off-by: Jason Yeh <jason.yeh@amd.com>
Signed-off-by: Robert Richter <robert.richter@amd.com>

arch/x86/oprofile/op_x86_model.h

@@ -23,6 +23,7 @@ struct op_msr {
 struct op_msrs {
 	struct op_msr *counters;
 	struct op_msr *controls;
+	struct op_msr *multiplex;
 };
 
 struct pt_regs;
@@ -35,6 +36,8 @@ struct oprofile_operations;
 struct op_x86_model_spec {
 	unsigned int	num_counters;
 	unsigned int	num_controls;
+	unsigned int	num_virt_counters;
+	unsigned int	num_virt_controls;
 	u64		reserved;
 	u16		event_mask;
 	int		(*init)(struct oprofile_operations *ops);
@@ -47,6 +50,10 @@ struct op_x86_model_spec {
 	void		(*start)(struct op_msrs const * const msrs);
 	void		(*stop)(struct op_msrs const * const msrs);
 	void		(*shutdown)(struct op_msrs const * const msrs);
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+	void		(*switch_ctrl)(struct op_x86_model_spec const *model,
+				       struct op_msrs const * const msrs);
+#endif
 };
 
 struct op_counter_config;