perf evsel: Fix missing exclude_{host,guest} setting

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.

Committer notes:

Fix 'perf test python' by adding a stub for evsel__find_pmu() in
tools/perf/util/python.c, document that it is used so far only for the
above reasons so that if anybody needs this in the python binding
usecases, we can revisit this.

Reported-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Link: http://lore.kernel.org/lkml/20211105205847.120950-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 2cfc293..3cc1f8f 100644 (file)
--- 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 846c827..dcc87c2 100644 (file)
--- 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 15bbec3..541889f 100644 (file)
--- 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;

diff --git a/tools/perf/util/python.c b/tools/perf/util/python.c
index 8feef3a..563a9ba 100644 (file)
--- a/tools/perf/util/python.c
+++ b/tools/perf/util/python.c
@@ -70,6 +70,18 @@ void perf_stat__collect_metric_expr(struct evlist *evsel_list)
 }
 
 /*
+ * This one is needed not to drag the PMU bandwagon, jevents generated
+ * pmu_sys_event_tables, etc and evsel__find_pmu() is used so far just for
+ * doing per PMU perf_event_attr.exclude_guest handling, not really needed, so
+ * far, for the perf python binding known usecases, revisit if this become
+ * necessary.
+ */
+struct perf_pmu *evsel__find_pmu(struct evsel *evsel __maybe_unused)
+{
+       return NULL;
+}
+
+/*
  * Add this one here not to drag util/metricgroup.c
  */
 int metricgroup__copy_metric_events(struct evlist *evlist, struct cgroup *cgrp,