[PATCH] perf kvm: Fix arm64 VM-EXIT event detection

[Haixin Yu]

A VM-EXIT event shall start at kvm:kvm_exit, and end with the next
kvm:kvm_entry. But it's reversed on arm64, which means the time running
guest code in fact.

Example:

 # perf kvm stat record -p 2772 -- sleep 1

Before this change:

 # perf kvm stat report

Analyze events for all VMs, all VCPUs:

    VM-EXIT Samples Samples%   Time%   Min Time   Max Time    Avg time

    IRQ      756     100.00%  100.00%   2.28us    3674.38us   1375.66us ( +-   4.34% )

Total Samples:756, Total events handled time:1039996.94us.

After:

 # perf kvm stat report

Analyze events for all VMs, all VCPUs:

    VM-EXIT Samples Samples%   Time%   Min Time   Max Time    Avg time

    IRQ     772      100.00%  100.00%   0.24us     62.86us    6.34us ( +-   3.55% )

Total Samples:772, Total events handled time:4890.80us.

IRQ average handled time decreases to 6us, which is a more rational result
as KVM handles IRQ by returning to guest directly.

Signed-off-by: Haixin Yu <yuhaixin.yhx at linux.alibaba.com>
---
 tools/perf/arch/arm64/util/kvm-stat.c | 24 +++---------------------
 tools/perf/builtin-kvm.c              |  2 +-
 2 files changed, 4 insertions(+), 22 deletions(-)

diff --git a/tools/perf/arch/arm64/util/kvm-stat.c b/tools/perf/arch/arm64/util/kvm-stat.c
index 6611aa21cba9..eeb659ceedc2 100644
--- a/tools/perf/arch/arm64/util/kvm-stat.c
+++ b/tools/perf/arch/arm64/util/kvm-stat.c
@@ -21,7 +21,7 @@ const char *kvm_events_tp[] = {
 	NULL,
 };
 
-static void event_get_key(struct evsel *evsel,
+void exit_event_get_key(struct evsel *evsel,
 			  struct perf_sample *sample,
 			  struct event_key *key)
 {
@@ -40,27 +40,9 @@ static void event_get_key(struct evsel *evsel,
 	}
 }
 
-static bool event_begin(struct evsel *evsel,
-			struct perf_sample *sample __maybe_unused,
-			struct event_key *key __maybe_unused)
-{
-	return evsel__name_is(evsel, kvm_entry_trace);
-}
-
-static bool event_end(struct evsel *evsel,
-		      struct perf_sample *sample,
-		      struct event_key *key)
-{
-	if (evsel__name_is(evsel, kvm_exit_trace)) {
-		event_get_key(evsel, sample, key);
-		return true;
-	}
-	return false;
-}
-
 static struct kvm_events_ops exit_events = {
-	.is_begin_event = event_begin,
-	.is_end_event	= event_end,
+	.is_begin_event = exit_event_begin,
+	.is_end_event	= exit_event_end,
 	.decode_key	= exit_event_decode_key,
 	.name		= "VM-EXIT"
 };
diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
index 71165036e4ca..498cd8e21134 100644
--- a/tools/perf/builtin-kvm.c
+++ b/tools/perf/builtin-kvm.c
@@ -615,7 +615,7 @@ static const char *get_filename_for_perf_kvm(void)
 
 #if defined(HAVE_KVM_STAT_SUPPORT) && defined(HAVE_LIBTRACEEVENT)
 
-void exit_event_get_key(struct evsel *evsel,
+void __weak exit_event_get_key(struct evsel *evsel,
 			struct perf_sample *sample,
 			struct event_key *key)
 {
-- 
2.34.1