[rfc 1/3] perf, x86: P4 PMU - describe config format

Cyrill Gorcunov
2010-11-23T22:48:11Z

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Add description of .config in a sake of RAW events.
At least this should bring some light to those who
will be reading this code.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
CC: Lin Ming <ming.m.lin@intel.com>
CC: Stephane Eranian <eranian@google.com>
CC: Peter Zijlstra <peterz@infradead.org>
---
arch/x86/include/asm/perf_event_p4.h | 62 ++++++++++++++++++++++++++++++-----
1 file changed, 54 insertions(+), 8 deletions(-)

Index: linux-2.6.git/arch/x86/include/asm/perf_event_p4.h
=====================================================================
--- linux-2.6.git.orig/arch/x86/include/asm/perf_event_p4.h
+++ linux-2.6.git/arch/x86/include/asm/perf_event_p4.h
@@ -744,14 +744,6 @@ enum P4_ESCR_EMASKS {
};

/*
- * P4 PEBS specifics (Replay Event only)
- *
- * Format (bits):
- * 0-6: metric from P4_PEBS_METRIC enum
- * 7 : reserved
- * 8 : reserved
- * 9-11 : reserved
- *
* Note we have UOP and PEBS bits reserved for now
* just in case if we will need them once
*/
@@ -788,5 +780,59 @@ enum P4_PEBS_METRIC {
P4_PEBS_METRIC__max
};

+/*
+ * Notes on internal configuration of ESCR+CCCR tuples
+ *
+ * Since P4 has quite the different architecture of
+ * performance registers in compare with "architectural"
+ * once and we have on 64 bits to keep configuration
+ * of performance event, the following trick is used.
+ *
+ * 1) Since both ESCR and CCCR registers have only low
+ * 32 bits valuable, we pack them into a single 64 bit
+ * configuration. Low 32 bits of such config correspond
+ * to low 32 bits of CCCR register and high 32 bits
+ * correspond to low 32 bits of ESCR register.
+ *
+ * 2) The meaning of every bit of such config field can
+ * be found in Intel SDM but it should be noted that
+ * we "borrow" some reserved bits for own usage and
+ * clean them or set to a proper value when we do
+ * a real write to hardware registers.
+ *
+ * 3) The format of bits of config is the following
+ * and should be either 0 or set to some predefined
+ * values:
+ *
+ * Low 32 bits
+ * -----------
+ * 0-6: P4_PEBS_METRIC enum
+ * 7-11: reserved
+ * 12: Active thread
+ * 13-15: reserved (ESCR select)
+ * 16-17: Compare
+ * 18: Complement
+ * 20-23: Threshold
+ * 24: Edge
+ * 25: reserved (FORCE_OVF)
+ * 26: reserved (OVF_PMI_T0)
+ * 27: reserved (OVF_PMI_T1)
+ * 28-29: reserved
+ * 30: reserved (Cascade)
+ * 31: reserved (OVF)
+ *
+ * High 32 bits
+ * ------------
+ * 0: reserved (T1_USR)
+ * 1: reserved (T1_OS)
+ * 2: reserved (T0_USR)
+ * 3: reserved (T0_OS)
+ * 4: Tag Enable
+ * 5-8: Tag Value
+ * 9-24: Event Mask (may use P4_ESCR_EMASK_BIT helper)
+ * 25-30: enum P4_EVENTS
+ * 31: reserved (HT thread)
+ */
+
#endif /* PERF_EVENT_P4_H */