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

Cyrill Gorcunov
2010-11-26T11:32:12Z

On Fri, Nov 26, 2010 at 2:14 PM, Cyrill Gorcunov <gorcunov@openvz.org> wrote:
> Stephane, this is a misprint, I'll update this comments on format
> (giod catch btw!). in real low 32 bits are considered as cccr in ht
> mode. wait a bit, i'll post update.
>
> On 11/26/10, Stephane Eranian <eranian@google.com> wrote:
...
>>> + *    Low 32 bits
>>> + *    -----------
>>> + *      0-6: P4_PEBS_METRIC enum
>>> + *     7-11:                    reserved
>>> + *       12: Active thread
>>
>> I don't understand bit 12. In the actual register, it
>> corresponds to the enable bit. Seems you're overriding
>> its usage. Do I interpret this as saying: 0 = enable when
>> running on thread0, 1=monitoring when running on thread1?
>> And if I don't care?
...
I believe it simply escaped quilt refresh somehow. Here is the 'refreshed'
copy (note the low bits 12-19 updated here).
---
perf, x86: P4 PMU - describe config format v2

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 | 63 ++++++++++++++++++++++++++++++-----
1 file changed, 55 insertions(+), 8 deletions(-)

Index: linux-2.6.tip/arch/x86/include/asm/perf_event_p4.h
===================================================================
--- linux-2.6.tip.orig/arch/x86/include/asm/perf_event_p4.h
+++ linux-2.6.tip/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 +780,60 @@ 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: reserved (Enable)
+ * 13-15: reserved (ESCR select)
+ * 16-17: Active Thread
+ * 18: Compare
+ * 19: 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 */