linux-kernel - [PATCH v2] perf bpf_counter: Fix opening of "any"(-1) CPU events

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Message-ID: <20251008162347.4005288-1-irogers@google.com>
Date: Wed,  8 Oct 2025 09:23:47 -0700
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Tengda Wu <wutengda@...weicloud.com>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: [PATCH v2] perf bpf_counter: Fix opening of "any"(-1) CPU events

The bperf BPF counter code doesn't handle "any"(-1) CPU events, always
wanting to aggregate a count against a CPU, which avoids the need for
atomics so let's not change that. Force evsels used for BPF counters
to require a CPU when not in system-wide mode so that the "any"(-1)
value isn't used during map propagation and evsel's CPU map matches
that of the PMU.

Fixes: b91917c0c6fa ("perf bpf_counter: Fix handling of cpumap fixing hybrid")
Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/builtin-stat.c     | 13 +++++++++++++
 tools/perf/util/bpf_counter.c |  1 +
 2 files changed, 14 insertions(+)

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 7006f848f87a..0fc6884c1bf1 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -2540,6 +2540,7 @@ int cmd_stat(int argc, const char **argv)
 	unsigned int interval, timeout;
 	const char * const stat_subcommands[] = { "record", "report" };
 	char errbuf[BUFSIZ];
+	struct evsel *counter;
 
 	setlocale(LC_ALL, "");
 
@@ -2797,6 +2798,18 @@ int cmd_stat(int argc, const char **argv)
 
 	evlist__warn_user_requested_cpus(evsel_list, target.cpu_list);
 
+	evlist__for_each_entry(evsel_list, counter) {
+		/*
+		 * Setup BPF counters to require CPUs as any(-1) isn't
+		 * supported. evlist__create_maps below will propagate this
+		 * information to the evsels. Note, evsel__is_bperf isn't yet
+		 * set up, and this change must happen early, so directly use
+		 * the bpf_counter variable.
+		 */
+		if (counter->bpf_counter)
+			counter->core.requires_cpu = true;
+	}
+
 	if (evlist__create_maps(evsel_list, &target) < 0) {
 		if (target__has_task(&target)) {
 			pr_err("Problems finding threads of monitor\n");
diff --git a/tools/perf/util/bpf_counter.c b/tools/perf/util/bpf_counter.c
index ca5d01b9017d..d3e5933b171b 100644
--- a/tools/perf/util/bpf_counter.c
+++ b/tools/perf/util/bpf_counter.c
@@ -495,6 +495,7 @@ static int bperf_reload_leader_program(struct evsel *evsel, int attr_map_fd,
 	 * following evsel__open_per_cpu call
 	 */
 	evsel->leader_skel = skel;
+	assert(!perf_cpu_map__has_any_cpu_or_is_empty(evsel->core.cpus));
 	evsel__open(evsel, evsel->core.cpus, evsel->core.threads);
 
 out:
-- 
2.51.0.710.ga91ca5db03-goog