[RFC][PATCH] perf, pebs: Add PEBS v3 record decoding

[Peter Zijlstra]

So seeing how I have both this series and Andi's SKL patches, I did the
below on top of them both.

Could someone try that?

---
Subject: perf, pebs: Add PEBS v3 record decoding
From: Peter Zijlstra <pet...@infradead.org>
Date: Tue May 12 15:18:18 CEST 2015

PEBS v3 as present on Skylake fixed the long standing issue of the
status bits. They now really reflect the events that generated the
record.

Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
---
 arch/x86/kernel/cpu/perf_event_intel_ds.c |   30 +++++++++++++++++++-----------
 1 file changed, 19 insertions(+), 11 deletions(-)

--- a/arch/x86/kernel/cpu/perf_event_intel_ds.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_ds.c
@@ -1034,6 +1034,9 @@ get_next_pebs_record_by_bit(void *base,
                struct pebs_record_nhm *p = at;
 
                if (test_bit(bit, (unsigned long *)&p->status)) {
+                       /* PEBS v3 has accurate status bits */
+                       if (x86_pmu.intel_cap.pebs_format >= 3)
+                               return at;
 
                        if (p->status == (1 << bit))
                                return at;
@@ -1055,20 +1058,18 @@ static void __intel_pmu_pebs_event(struc
 {
        struct perf_sample_data data;
        struct pt_regs regs;
-       int i;
        void *at = get_next_pebs_record_by_bit(base, top, bit);
 
        if (!intel_pmu_save_and_restart(event) &&
            !(event->hw.flags & PERF_X86_EVENT_AUTO_RELOAD))
                return;
 
-       if (count > 1) {
-               for (i = 0; i < count - 1; i++) {
-                       setup_pebs_sample_data(event, iregs, at, &data, &regs);
-                       perf_event_output(event, &data, &regs);
-                       at += x86_pmu.pebs_record_size;
-                       at = get_next_pebs_record_by_bit(at, top, bit);
-               }
+       while (count > 1) {
+               setup_pebs_sample_data(event, iregs, at, &data, &regs);
+               perf_event_output(event, &data, &regs);
+               at += x86_pmu.pebs_record_size;
+               at = get_next_pebs_record_by_bit(at, top, bit);
+               count--;
        }
 
        setup_pebs_sample_data(event, iregs, at, &data, &regs);
@@ -1124,9 +1125,9 @@ static void intel_pmu_drain_pebs_nhm(str
        struct debug_store *ds = cpuc->ds;
        struct perf_event *event;
        void *base, *at, *top;
-       int bit;
        short counts[MAX_PEBS_EVENTS] = {};
        short error[MAX_PEBS_EVENTS] = {};
+       int bit, i;
 
        if (!x86_pmu.pebs_active)
                return;
@@ -1142,6 +1143,15 @@ static void intel_pmu_drain_pebs_nhm(str
        for (at = base; at < top; at += x86_pmu.pebs_record_size) {
                struct pebs_record_nhm *p = at;
 
+               /* PEBS v3 has accurate status bits */
+               if (x86_pmu.intel_cap.pebs_format >= 3) {
+                       for_each_set_bit(bit, (unsigned long *)&p->status,
+                                        MAX_PEBS_EVENTS)
+                               counts[bit]++;
+
+                       continue;
+               }
+
                bit = find_first_bit((unsigned long *)&p->status,
                                        x86_pmu.max_pebs_events);
                if (bit >= x86_pmu.max_pebs_events)
@@ -1171,8 +1181,6 @@ static void intel_pmu_drain_pebs_nhm(str
                        pebs_status = p->status & cpuc->pebs_enabled;
                        pebs_status &= (1ULL << MAX_PEBS_EVENTS) - 1;
                        if (pebs_status != (1 << bit)) {
-                               u8 i;
-
                                for_each_set_bit(i, (unsigned long 
*)&pebs_status,
                                                 MAX_PEBS_EVENTS)
                                        error[i]++;
--
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