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Subject[PATCH v4] perf evsel: Fix missing exclude_{host,guest} setting
Date
The current logic for the perf missing feature has a bug that it can
wrongly clear some modifiers like G or H. Actually some PMUs don't
support any filtering or exclusion while others do. But we check it
as a global feature.

For example, the cycles event can have 'G' modifier to enable it only
in the guest mode on x86. When you don't run any VMs it'll return 0.

# perf stat -a -e cycles:G sleep 1

Performance counter stats for 'system wide':

0 cycles:G

1.000721670 seconds time elapsed

But when it's used with other pmu events that don't support G modifier,
it'll be reset and return non-zero values.

# perf stat -a -e cycles:G,msr/tsc/ sleep 1

Performance counter stats for 'system wide':

538,029,960 cycles:G
16,924,010,738 msr/tsc/

1.001815327 seconds time elapsed

This is because of the missing feature detection logic being global.
Add a hashmap to set pmu-specific exclude_host/guest features.

Reported-by: Stephane Eranian <eranian@google.com>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
v4 changes)
* add pmu->missing_features.exclude_guest
* bail out if evsel->exclude_GH is set

v3 changes)
* check memory allocation failure
* add more NULL check

v2 changes)
* change to enum perf_missing_pmu_features
* pass NULL to hashmap__find() to skip checking
* add a blank line after declaration

tools/perf/util/evsel.c | 27 ++++++++++++++++++++++-----
tools/perf/util/evsel.h | 4 ++++
tools/perf/util/pmu.h | 4 ++++
3 files changed, 30 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 2cfc2935d1d2..3cc1f8fcf15c 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1824,7 +1824,7 @@ static void evsel__disable_missing_features(struct evsel *evsel)
evsel->open_flags &= ~(unsigned long)PERF_FLAG_FD_CLOEXEC;
if (perf_missing_features.mmap2)
evsel->core.attr.mmap2 = 0;
- if (perf_missing_features.exclude_guest)
+ if (evsel->pmu && evsel->pmu->missing_features.exclude_guest)
evsel->core.attr.exclude_guest = evsel->core.attr.exclude_host = 0;
if (perf_missing_features.lbr_flags)
evsel->core.attr.branch_sample_type &= ~(PERF_SAMPLE_BRANCH_NO_FLAGS |
@@ -1917,10 +1917,27 @@ bool evsel__detect_missing_features(struct evsel *evsel)
perf_missing_features.mmap2 = true;
pr_debug2_peo("switching off mmap2\n");
return true;
- } else if (!perf_missing_features.exclude_guest &&
- (evsel->core.attr.exclude_guest || evsel->core.attr.exclude_host)) {
- perf_missing_features.exclude_guest = true;
- pr_debug2_peo("switching off exclude_guest, exclude_host\n");
+ } else if ((evsel->core.attr.exclude_guest || evsel->core.attr.exclude_host) &&
+ (evsel->pmu == NULL || evsel->pmu->missing_features.exclude_guest)) {
+ if (evsel->pmu == NULL) {
+ evsel->pmu = evsel__find_pmu(evsel);
+ if (evsel->pmu)
+ evsel->pmu->missing_features.exclude_guest = true;
+ else {
+ /* we cannot find PMU, disable attrs now */
+ evsel->core.attr.exclude_host = false;
+ evsel->core.attr.exclude_guest = false;
+ }
+ }
+
+ if (evsel->exclude_GH) {
+ pr_debug2_peo("PMU has no exclude_host/guest support, bailing out\n");
+ return false;
+ }
+ if (!perf_missing_features.exclude_guest) {
+ perf_missing_features.exclude_guest = true;
+ pr_debug2_peo("switching off exclude_guest, exclude_host\n");
+ }
return true;
} else if (!perf_missing_features.sample_id_all) {
perf_missing_features.sample_id_all = true;
diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index 846c827934de..dcc87c2881b8 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -22,6 +22,7 @@ struct target;
struct hashmap;
struct bperf_leader_bpf;
struct bperf_follower_bpf;
+struct perf_pmu;

typedef int (evsel__sb_cb_t)(union perf_event *event, void *data);

@@ -153,6 +154,9 @@ struct evsel {
};
unsigned long open_flags;
int precise_ip_original;
+
+ /* for missing_features */
+ struct perf_pmu *pmu;
};

struct perf_missing_features {
diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
index 15bbec3a9959..541889fa9f9c 100644
--- a/tools/perf/util/pmu.h
+++ b/tools/perf/util/pmu.h
@@ -49,6 +49,10 @@ struct perf_pmu {
struct list_head caps; /* HEAD struct perf_pmu_caps -> list */
struct list_head list; /* ELEM */
struct list_head hybrid_list;
+
+ struct {
+ bool exclude_guest;
+ } missing_features;
};

extern struct perf_pmu perf_pmu__fake;
--
2.34.0.rc0.344.g81b53c2807-goog
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