[PATCH bpf-next v3 0/2] bpftool: Fix sparse CPU IDs

[PATCH bpf-next v3 0/2] bpftool: Fix sparse CPU IDs

[Hui Su]

bpftool currently assumes that possible CPU IDs are dense. This is not
true when the possible CPU mask itself is sparse, such as 0,2-3. In that
case, per-CPU map output labels and prog profile event-array keys can
refer to the wrong logical CPUs.

The first patch keeps dense per-CPU buffer slots separate from logical CPU
IDs when printing per-CPU map values. The parsed CPU count is passed
together with the logical CPU IDs so that output labels and loop bounds use
the same possible-CPU mask.

The second patch applies the same distinction to prog profile. Userspace
keeps a compact CPU count for per-CPU result buffers, while perf events are
created for the actual logical CPU IDs and PERF_EVENT_ARRAY keys use the
logical CPU ID span. The current per-CPU perf event grouping in bpf-next is
preserved.

Changes in v3:
- Rebase the series onto bpf-next/master as requested by Andrii.
- Adapt the prog profile fix to current bpf-next while preserving its
  per-CPU perf event grouping and scaled-value accounting.
- Pass the parsed CPU count through the per-CPU map output helpers.
- Match the existing bpftool memory-allocation error style.
- Pass profile_cpu_ids directly to get_possible_cpu_ids().
- Move testing details from individual patches to the cover letter.

Previous versions:
v2: https://lore.kernel.org/lkml/20260918102052.1247819-1-sh_def@163.com/

Testing:
- PASS: Host and ARM64 bpftool builds, bpftool Documentation build, bash
  syntax, and diff checks.
- PASS: ARM64 QEMU with a synthetic possible/present/online mask of 0,2-3;
  plain, JSON, and BTF per-CPU map output reported CPUs 0,2,3, and prog
  profile reached perf_event_open for CPUs 0,2,3. QEMU did not provide
  usable PMU counts.

Hui Su (2):
  bpftool: Fix CPU IDs in per-CPU map output
  bpftool: Fix sparse CPU IDs in prog profile

 tools/bpf/bpftool/common.c                | 40 ++++++++++
 tools/bpf/bpftool/main.h                  |  1 +
 tools/bpf/bpftool/map.c                   | 95 +++++++++++++++--------
 tools/bpf/bpftool/prog.c                  | 51 +++++++-----
 tools/bpf/bpftool/skeleton/profiler.bpf.c |  8 +-
 5 files changed, 140 insertions(+), 55 deletions(-)


base-commit: 79dc258c9392051420a26f1504c647bd3d27c66a
-- 
2.55.0

[PATCH bpf-next v3 1/2] bpftool: Fix CPU IDs in per-CPU map output

[Hui Su]

bpftool uses dense per-CPU value-buffer slots when printing per-CPU map
values. It also uses the slot index as the CPU ID, which produces
incorrect labels when the possible CPU mask is sparse, such as 0,2-3.

Parse the possible CPU mask and use the corresponding logical CPU ID in
plain, JSON, and BTF-formatted output. Keep the dense slot index for
accessing the per-CPU value buffer.

Pass the parsed CPU count together with the CPU ID array so that the
printed CPU IDs and loop bounds come from the same possible-CPU mask.
Propagate CPU-ID lookup and map output errors through the shared output
path to its callers.

Fixes: 71bb428fe2c1 ("tools: bpf: add bpftool")
Link: https://lore.kernel.org/bpf/20260813155131.1022745-3-sh_def@163.com/
Signed-off-by: Hui Su <sh_def@163.com>
---
 tools/bpf/bpftool/common.c | 40 ++++++++++++++++
 tools/bpf/bpftool/main.h   |  1 +
 tools/bpf/bpftool/map.c    | 95 +++++++++++++++++++++++++-------------
 3 files changed, 103 insertions(+), 33 deletions(-)

diff --git a/tools/bpf/bpftool/common.c b/tools/bpf/bpftool/common.c
index ef366ccc9650..f9b87efa7c9a 100644
--- a/tools/bpf/bpftool/common.c
+++ b/tools/bpf/bpftool/common.c
@@ -31,6 +31,7 @@
 #include <bpf/bpf.h>
 #include <bpf/hashmap.h>
 #include <bpf/libbpf.h> /* libbpf_num_possible_cpus */
+#include <bpf/libbpf_internal.h>
 #include <bpf/btf.h>
 #include <zlib.h>
 
@@ -655,6 +656,45 @@ unsigned int get_possible_cpus(void)
 	return cpus;
 }
 
+int get_possible_cpu_ids(int **cpu_ids)
+{
+	const char *possible_cpus_file = "/sys/devices/system/cpu/possible";
+	bool *mask = NULL;
+	int mask_sz, nr_cpus = 0;
+	int *ids = NULL;
+	int i, res;
+
+	*cpu_ids = NULL;
+
+	res = parse_cpu_mask_file(possible_cpus_file, &mask, &mask_sz);
+	if (res) {
+		p_err("failed to parse possible CPU mask: %s", strerror(-res));
+		return res;
+	}
+
+	for (i = 0; i < mask_sz; i++)
+		nr_cpus += mask[i];
+
+	ids = calloc(nr_cpus, sizeof(*ids));
+	if (!ids) {
+		p_err("mem alloc failed");
+		res = -ENOMEM;
+		goto out;
+	}
+
+	for (i = 0, nr_cpus = 0; i < mask_sz; i++) {
+		if (mask[i])
+			ids[nr_cpus++] = i;
+	}
+	*cpu_ids = ids;
+	ids = NULL;
+	res = nr_cpus;
+out:
+	free(ids);
+	free(mask);
+	return res;
+}
+
 static char *
 ifindex_to_name_ns(__u32 ifindex, __u32 ns_dev, __u32 ns_ino, char *buf)
 {
diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
index 9315a1db1f7c..48eedcb9f6c0 100644
--- a/tools/bpf/bpftool/main.h
+++ b/tools/bpf/bpftool/main.h
@@ -216,6 +216,7 @@ void print_hex_data_json(uint8_t *data, size_t len);
 
 unsigned int get_page_size(void);
 unsigned int get_possible_cpus(void);
+int get_possible_cpu_ids(int **cpu_ids);
 const char *
 ifindex_to_arch(__u32 ifindex, __u64 ns_dev, __u64 ns_ino, const char **opt);
 
diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
index 684a8fb72414..20d59eab09a1 100644
--- a/tools/bpf/bpftool/map.c
+++ b/tools/bpf/bpftool/map.c
@@ -70,7 +70,7 @@ static void *alloc_value(struct bpf_map_info *info)
 
 static int do_dump_btf(const struct btf_dumper *d,
 		       struct bpf_map_info *map_info, void *key,
-		       void *value)
+		       void *value, const int *cpu_ids, int cpu_cnt)
 {
 	__u32 value_id;
 	int ret = 0;
@@ -93,15 +93,15 @@ static int do_dump_btf(const struct btf_dumper *d,
 		jsonw_name(d->jw, "value");
 		ret = btf_dumper_type(d, value_id, value);
 	} else {
-		unsigned int i, n, step;
+		unsigned int step;
+		int i;
 
 		jsonw_name(d->jw, "values");
 		jsonw_start_array(d->jw);
-		n = get_possible_cpus();
 		step = round_up(map_info->value_size, 8);
-		for (i = 0; i < n; i++) {
+		for (i = 0; i < cpu_cnt; i++) {
 			jsonw_start_object(d->jw);
-			jsonw_int_field(d->jw, "cpu", i);
+			jsonw_int_field(d->jw, "cpu", cpu_ids[i]);
 			jsonw_name(d->jw, "value");
 			ret = btf_dumper_type(d, value_id, value + i * step);
 			jsonw_end_object(d->jw);
@@ -130,7 +130,8 @@ static json_writer_t *get_btf_writer(void)
 }
 
 static void print_entry_json(struct bpf_map_info *info, unsigned char *key,
-			     unsigned char *value, struct btf *btf)
+			     unsigned char *value, struct btf *btf,
+			     const int *cpu_ids, int cpu_cnt)
 {
 	jsonw_start_object(json_wtr);
 
@@ -150,12 +151,12 @@ static void print_entry_json(struct bpf_map_info *info, unsigned char *key,
 			};
 
 			jsonw_name(json_wtr, "formatted");
-			do_dump_btf(&d, info, key, value);
+			do_dump_btf(&d, info, key, value, cpu_ids, cpu_cnt);
 		}
 	} else {
-		unsigned int i, n, step;
+		unsigned int step;
+		int i;
 
-		n = get_possible_cpus();
 		step = round_up(info->value_size, 8);
 
 		jsonw_name(json_wtr, "key");
@@ -163,10 +164,10 @@ static void print_entry_json(struct bpf_map_info *info, unsigned char *key,
 
 		jsonw_name(json_wtr, "values");
 		jsonw_start_array(json_wtr);
-		for (i = 0; i < n; i++) {
+		for (i = 0; i < cpu_cnt; i++) {
 			jsonw_start_object(json_wtr);
 
-			jsonw_int_field(json_wtr, "cpu", i);
+			jsonw_int_field(json_wtr, "cpu", cpu_ids[i]);
 
 			jsonw_name(json_wtr, "value");
 			print_hex_data_json(value + i * step,
@@ -183,7 +184,7 @@ static void print_entry_json(struct bpf_map_info *info, unsigned char *key,
 			};
 
 			jsonw_name(json_wtr, "formatted");
-			do_dump_btf(&d, info, key, value);
+			do_dump_btf(&d, info, key, value, cpu_ids, cpu_cnt);
 		}
 	}
 
@@ -245,7 +246,7 @@ print_entry_error(struct bpf_map_info *map_info, void *key, int lookup_errno)
 }
 
 static void print_entry_plain(struct bpf_map_info *info, unsigned char *key,
-			      unsigned char *value)
+			      unsigned char *value, const int *cpu_ids, int cpu_cnt)
 {
 	if (!map_is_per_cpu(info->type)) {
 		bool single_line, break_names;
@@ -273,9 +274,9 @@ static void print_entry_plain(struct bpf_map_info *info, unsigned char *key,
 
 		printf("\n");
 	} else {
-		unsigned int i, n, step;
+		unsigned int step;
+		int i;
 
-		n = get_possible_cpus();
 		step = round_up(info->value_size, 8);
 
 		if (info->key_size) {
@@ -284,9 +285,9 @@ static void print_entry_plain(struct bpf_map_info *info, unsigned char *key,
 			printf("\n");
 		}
 		if (info->value_size) {
-			for (i = 0; i < n; i++) {
-				printf("value (CPU %02u):%c",
-				       i, info->value_size > 16 ? '\n' : ' ');
+			for (i = 0; i < cpu_cnt; i++) {
+				printf("value (CPU %02d):%c",
+				       cpu_ids[i], info->value_size > 16 ? '\n' : ' ');
 				fprint_hex(stdout, value + i * step,
 					   info->value_size, " ");
 				printf("\n");
@@ -742,7 +743,7 @@ static int do_show(int argc, char **argv)
 
 static int dump_map_elem(int fd, void *key, void *value,
 			 struct bpf_map_info *map_info, struct btf *btf,
-			 json_writer_t *btf_wtr)
+			 json_writer_t *btf_wtr, const int *cpu_ids, int cpu_cnt)
 {
 	if (bpf_map_lookup_elem(fd, key, value)) {
 		print_entry_error(map_info, key, errno);
@@ -750,7 +751,7 @@ static int dump_map_elem(int fd, void *key, void *value,
 	}
 
 	if (json_output) {
-		print_entry_json(map_info, key, value, btf);
+		print_entry_json(map_info, key, value, btf, cpu_ids, cpu_cnt);
 	} else if (btf) {
 		struct btf_dumper d = {
 			.btf = btf,
@@ -758,9 +759,9 @@ static int dump_map_elem(int fd, void *key, void *value,
 			.is_plain_text = true,
 		};
 
-		do_dump_btf(&d, map_info, key, value);
+		do_dump_btf(&d, map_info, key, value, cpu_ids, cpu_cnt);
 	} else {
-		print_entry_plain(map_info, key, value);
+		print_entry_plain(map_info, key, value, cpu_ids, cpu_cnt);
 	}
 
 	return 0;
@@ -833,6 +834,8 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
 	void *key, *value, *prev_key;
 	unsigned int num_elems = 0;
 	struct btf *btf = NULL;
+	int *cpu_ids = NULL;
+	int cpu_cnt = 0;
 	int err;
 
 	key = malloc(info->key_size);
@@ -845,6 +848,14 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
 
 	prev_key = NULL;
 
+	if (map_is_per_cpu(info->type)) {
+		cpu_cnt = get_possible_cpu_ids(&cpu_ids);
+		if (cpu_cnt < 0) {
+			err = cpu_cnt;
+			goto exit_free;
+		}
+	}
+
 	if (wtr) {
 		err = get_map_kv_btf(info, &btf);
 		if (err) {
@@ -876,7 +887,8 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
 				err = 0;
 			break;
 		}
-		if (!dump_map_elem(fd, key, value, info, btf, wtr))
+		if (!dump_map_elem(fd, key, value, info, btf, wtr,
+				   cpu_ids, cpu_cnt))
 			num_elems++;
 		prev_key = key;
 	}
@@ -893,6 +905,7 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
 exit_free:
 	free(key);
 	free(value);
+	free(cpu_ids);
 	free_map_kv_btf(btf);
 
 	return err;
@@ -1035,17 +1048,30 @@ static int do_update(int argc, char **argv)
 	return err;
 }
 
-static void print_key_value(struct bpf_map_info *info, void *key,
-			    void *value)
+static int print_key_value(struct bpf_map_info *info, void *key,
+			   void *value)
 {
 	json_writer_t *btf_wtr;
 	struct btf *btf;
+	int *cpu_ids = NULL;
+	int cpu_cnt = 0;
+	int err = 0;
 
-	if (get_map_kv_btf(info, &btf))
-		return;
+	if (map_is_per_cpu(info->type)) {
+		cpu_cnt = get_possible_cpu_ids(&cpu_ids);
+
+		if (cpu_cnt < 0) {
+			err = cpu_cnt;
+			goto out;
+		}
+	}
+
+	err = get_map_kv_btf(info, &btf);
+	if (err)
+		goto out;
 
 	if (json_output) {
-		print_entry_json(info, key, value, btf);
+		print_entry_json(info, key, value, btf, cpu_ids, cpu_cnt);
 	} else if (btf) {
 		/* if here json_wtr wouldn't have been initialised,
 		 * so let's create separate writer for btf
@@ -1055,7 +1081,7 @@ static void print_key_value(struct bpf_map_info *info, void *key,
 			p_info("failed to create json writer for btf. falling back to plain output");
 			free_map_kv_btf(btf);
 			btf = NULL;
-			print_entry_plain(info, key, value);
+			print_entry_plain(info, key, value, cpu_ids, cpu_cnt);
 		} else {
 			struct btf_dumper d = {
 				.btf = btf,
@@ -1063,13 +1089,16 @@ static void print_key_value(struct bpf_map_info *info, void *key,
 				.is_plain_text = true,
 			};
 
-			do_dump_btf(&d, info, key, value);
+			do_dump_btf(&d, info, key, value, cpu_ids, cpu_cnt);
 			jsonw_destroy(&btf_wtr);
 		}
 	} else {
-		print_entry_plain(info, key, value);
+		print_entry_plain(info, key, value, cpu_ids, cpu_cnt);
 	}
 	free_map_kv_btf(btf);
+out:
+	free(cpu_ids);
+	return err;
 }
 
 static int do_lookup(int argc, char **argv)
@@ -1114,7 +1143,7 @@ static int do_lookup(int argc, char **argv)
 	}
 
 	/* here means bpf_map_lookup_elem() succeeded */
-	print_key_value(&info, key, value);
+	err = print_key_value(&info, key, value);
 
 exit_free:
 	free(key);
@@ -1404,7 +1433,7 @@ static int do_pop_dequeue(int argc, char **argv)
 		goto exit_free;
 	}
 
-	print_key_value(&info, key, value);
+	err = print_key_value(&info, key, value);
 
 exit_free:
 	free(key);
-- 
2.55.0

[PATCH bpf-next v3 2/2] bpftool: Fix sparse CPU IDs in prog profile

[Hui Su]

bpftool prog profile currently treats the number of possible CPUs as
both the logical CPU ID range and the stride of the perf event array.
That misses valid logical CPUs when the possible CPU mask is sparse,
such as 0,2-3, and can use incorrect PERF_EVENT_ARRAY keys.

Keep the compact possible CPU count for per-CPU result buffers, while
enumerating the actual logical CPU IDs when creating per-CPU perf event
groups. Use the maximum logical CPU ID plus one as the metric stride in
the PERF_EVENT_ARRAY.

This keeps the current per-CPU event grouping intact while separating
the compact per-CPU buffer index from the logical CPU ID and event-array
key. Report the logical CPU ID when a per-CPU event was not counted.

Fixes: 47c09d6a9f67 ("bpftool: Introduce "prog profile" command")
Link: https://lore.kernel.org/bpf/20260813160858.1042834-3-sh_def@163.com/
Signed-off-by: Hui Su <sh_def@163.com>
---
 tools/bpf/bpftool/prog.c                  | 51 +++++++++++++++--------
 tools/bpf/bpftool/skeleton/profiler.bpf.c |  8 ++--
 2 files changed, 37 insertions(+), 22 deletions(-)

diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index 000774835b10..24e40dfab469 100644
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -2164,6 +2164,9 @@ struct profile_metric {
 };
 
 static __u64 profile_total_count;
+static int profile_cpu_cnt;
+static int *profile_cpu_ids;
+static int profile_cpu_id_span;
 
 #define MAX_NUM_PROFILE_METRICS 4
 
@@ -2200,7 +2203,7 @@ static int profile_parse_metrics(int argc, char **argv)
 
 static int profile_read_values(struct profiler_bpf *obj)
 {
-	__u32 m, cpu, num_cpu = obj->rodata->num_cpu;
+	__u32 m, cpu, num_cpu = profile_cpu_cnt;
 	int reading_map_fd, count_map_fd;
 	__u64 counts[num_cpu];
 	__u32 key = 0;
@@ -2235,8 +2238,8 @@ static int profile_read_values(struct profiler_bpf *obj)
 		for (cpu = 0; cpu < num_cpu; cpu++) {
 			val = &values[cpu];
 			if (counts[cpu] && !val->running) {
-				p_err("perf event %s was not counted on CPU %u",
-				      metrics[m].name, cpu);
+				p_err("perf event %s was not counted on CPU %d",
+				      metrics[m].name, profile_cpu_ids[cpu]);
 				return -EAGAIN;
 			}
 			metrics[m].val.enabled += val->enabled;
@@ -2394,6 +2397,7 @@ static void profile_close_perf_events(void)
 		close(profile_perf_events[i]);
 
 	free(profile_perf_events);
+	profile_perf_events = NULL;
 	profile_perf_event_cnt = 0;
 }
 
@@ -2427,13 +2431,12 @@ static int profile_open_perf_event(int mid, int cpu,
 
 static int profile_open_perf_events(struct profiler_bpf *obj)
 {
-	__u32 num_cpu = obj->rodata->num_cpu;
 	__u32 map_key;
 	unsigned int cpu, m;
 	int group_fd, map_fd, pmu_fd;
 	int err;
 
-	profile_perf_events = calloc(num_cpu * obj->rodata->num_metric,
+	profile_perf_events = calloc(profile_cpu_cnt * obj->rodata->num_metric,
 				     sizeof(*profile_perf_events));
 	if (!profile_perf_events) {
 		p_err("failed to allocate memory for perf_event array: %s",
@@ -2442,32 +2445,34 @@ static int profile_open_perf_events(struct profiler_bpf *obj)
 	}
 
 	map_fd = bpf_map__fd(obj->maps.events);
-	for (cpu = 0; cpu < num_cpu; cpu++) {
+	for (cpu = 0; cpu < (unsigned int)profile_cpu_cnt; cpu++) {
+		int cpu_id = profile_cpu_ids[cpu];
+
 		group_fd = -1;
-		map_key = cpu;
+		map_key = cpu_id;
 		for (m = 0; m < ARRAY_SIZE(metrics); m++) {
 			if (!metrics[m].selected)
 				continue;
 
-			pmu_fd = profile_open_perf_event(m, cpu, map_fd, group_fd,
+			pmu_fd = profile_open_perf_event(m, cpu_id, map_fd, group_fd,
 						     map_key);
 			if (pmu_fd == -ENODEV && group_fd < 0)
 				break;
 			if (pmu_fd < 0) {
-				p_err("failed to add event %s to group on CPU %u: %s",
-				      metrics[m].name, cpu, strerror(-pmu_fd));
+				p_err("failed to add event %s to group on CPU %d: %s",
+				      metrics[m].name, cpu_id, strerror(-pmu_fd));
 				return pmu_fd;
 			}
 			if (group_fd < 0)
 				group_fd = pmu_fd;
-			map_key += num_cpu;
+			map_key += profile_cpu_id_span;
 		}
 		if (group_fd < 0)
 			continue;
 		if (ioctl(group_fd, PERF_EVENT_IOC_ENABLE, PERF_IOC_FLAG_GROUP)) {
 			err = -errno;
-			p_err("failed to enable perf event group on CPU %u: %s",
-			      cpu, strerror(-err));
+			p_err("failed to enable perf event group on CPU %d: %s",
+			      cpu_id, strerror(-err));
 			return err;
 		}
 	}
@@ -2486,6 +2491,10 @@ static int profile_print_and_cleanup(void)
 
 	close(profile_tgt_fd);
 	free(profile_tgt_name);
+	free(profile_cpu_ids);
+	profile_cpu_ids = NULL;
+	profile_cpu_cnt = 0;
+	profile_cpu_id_span = 0;
 	return err;
 }
 
@@ -2496,7 +2505,7 @@ static void int_exit(int signo)
 
 static int do_profile(int argc, char **argv)
 {
-	int num_metric, num_cpu, err = -1;
+	int num_metric, err = -1;
 	struct bpf_program *prog;
 	unsigned long duration;
 	char *endptr;
@@ -2527,11 +2536,12 @@ static int do_profile(int argc, char **argv)
 	if (num_metric <= 0)
 		goto out;
 
-	num_cpu = libbpf_num_possible_cpus();
-	if (num_cpu <= 0) {
+	profile_cpu_cnt = get_possible_cpu_ids(&profile_cpu_ids);
+	if (profile_cpu_cnt <= 0) {
 		p_err("failed to identify number of CPUs");
 		goto out;
 	}
+	profile_cpu_id_span = profile_cpu_ids[profile_cpu_cnt - 1] + 1;
 
 	profile_obj = profiler_bpf__open();
 	if (!profile_obj) {
@@ -2539,11 +2549,12 @@ static int do_profile(int argc, char **argv)
 		goto out;
 	}
 
-	profile_obj->rodata->num_cpu = num_cpu;
 	profile_obj->rodata->num_metric = num_metric;
+	profile_obj->rodata->cpu_id_span = profile_cpu_id_span;
 
 	/* adjust map sizes */
-	bpf_map__set_max_entries(profile_obj->maps.events, num_metric * num_cpu);
+	bpf_map__set_max_entries(profile_obj->maps.events,
+				 num_metric * profile_cpu_id_span);
 	bpf_map__set_max_entries(profile_obj->maps.fentry_readings, num_metric);
 	bpf_map__set_max_entries(profile_obj->maps.accum_readings, num_metric);
 	bpf_map__set_max_entries(profile_obj->maps.counts, 1);
@@ -2589,6 +2600,10 @@ static int do_profile(int argc, char **argv)
 		profiler_bpf__destroy(profile_obj);
 	close(profile_tgt_fd);
 	free(profile_tgt_name);
+	free(profile_cpu_ids);
+	profile_cpu_ids = NULL;
+	profile_cpu_cnt = 0;
+	profile_cpu_id_span = 0;
 	return err;
 }
 
diff --git a/tools/bpf/bpftool/skeleton/profiler.bpf.c b/tools/bpf/bpftool/skeleton/profiler.bpf.c
index 6685e7252fb5..0d47a9bdc5b4 100644
--- a/tools/bpf/bpftool/skeleton/profiler.bpf.c
+++ b/tools/bpf/bpftool/skeleton/profiler.bpf.c
@@ -10,7 +10,7 @@ struct bpf_perf_event_value___local {
 	__u64 running;
 } __attribute__((preserve_access_index));
 
-/* map of perf event fds, num_cpu * num_metric entries */
+/* map of perf event fds, cpu_id_span * num_metric entries */
 struct {
 	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
 	__uint(key_size, sizeof(u32));
@@ -38,8 +38,8 @@ struct {
 	__uint(value_size, sizeof(u64));
 } counts SEC(".maps");
 
-const volatile __u32 num_cpu = 1;
 const volatile __u32 num_metric = 1;
+const volatile __u32 cpu_id_span = 1;
 #define MAX_NUM_METRICS 4
 
 SEC("fentry/XXX")
@@ -60,7 +60,7 @@ int BPF_PROG(fentry_XXX)
 						sizeof(*reading));
 		if (err)
 			return 0;
-		key += num_cpu;
+		key += cpu_id_span;
 	}
 
 	return 0;
@@ -100,7 +100,7 @@ int BPF_PROG(fexit_XXX)
 
 	/* read all events before updating the maps, to reduce error */
 	for (i = 0; i < num_metric && i < MAX_NUM_METRICS; i++) {
-		err = bpf_perf_event_read_value(&events, cpu + i * num_cpu,
+		err = bpf_perf_event_read_value(&events, cpu + i * cpu_id_span,
 						(void *)(readings + i),
 						sizeof(*readings));
 		if (err)
-- 
2.55.0

Re: [PATCH bpf-next v3 2/2] bpftool: Fix sparse CPU IDs in prog profile

[bot+bpf-ci]

[-- Attachment #1: Type: text/plain, Size: 1649 bytes --]

> diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
> index 000774835b10..24e40dfab469 100644
> --- a/tools/bpf/bpftool/prog.c
> +++ b/tools/bpf/bpftool/prog.c

[ ... ]

> @@ -2394,6 +2397,7 @@ static void profile_close_perf_events(void)
>  		close(profile_perf_events[i]);
>
>  	free(profile_perf_events);
> +	profile_perf_events = NULL;
>  	profile_perf_event_cnt = 0;
>  }

This isn't a bug, but is the new 'profile_perf_events = NULL;' needed
for the sparse-CPU fix, or would it read better as its own patch (or at
least a changelog line), since the rest of the hunk set is about CPU
IDs?

[ ... ]

> @@ -2486,6 +2491,10 @@ static int profile_print_and_cleanup(void)
>
>  	close(profile_tgt_fd);
>  	free(profile_tgt_name);
> +	free(profile_cpu_ids);
> +	profile_cpu_ids = NULL;
> +	profile_cpu_cnt = 0;
> +	profile_cpu_id_span = 0;
>  	return err;
>  }

[ ... ]

> @@ -2589,6 +2600,10 @@ static int do_profile(int argc, char **argv)
>  		profiler_bpf__destroy(profile_obj);
>  	close(profile_tgt_fd);
>  	free(profile_tgt_name);
> +	free(profile_cpu_ids);
> +	profile_cpu_ids = NULL;
> +	profile_cpu_cnt = 0;
> +	profile_cpu_id_span = 0;
>  	return err;
>  }

This isn't a bug, but could the 'profile_cpu_cnt = 0' /
'profile_cpu_id_span = 0' stores be dropped, given nothing reads them
after either return and the adjacent statics (profile_tgt_name,
profile_obj) are left alone?

[ ... ]


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/35804155043

Re: [PATCH bpf-next v3 0/2] bpftool: Fix sparse CPU IDs

[patchwork-bot+netdevbpf]

Hello:

This series was applied to bpf/bpf-next.git (master)
by Kumar Kartikeya Dwivedi <memxor@gmail.com>:

On Wed, 23 Sep 2026 09:42:41 +0900 you wrote:
> bpftool currently assumes that possible CPU IDs are dense. This is not
> true when the possible CPU mask itself is sparse, such as 0,2-3. In that
> case, per-CPU map output labels and prog profile event-array keys can
> refer to the wrong logical CPUs.
> 
> The first patch keeps dense per-CPU buffer slots separate from logical CPU
> IDs when printing per-CPU map values. The parsed CPU count is passed
> together with the logical CPU IDs so that output labels and loop bounds use
> the same possible-CPU mask.
> 
> [...]

Here is the summary with links:
  - [bpf-next,v3,1/2] bpftool: Fix CPU IDs in per-CPU map output
    https://git.kernel.org/bpf/bpf-next/c/dbf8cef936c7
  - [bpf-next,v3,2/2] bpftool: Fix sparse CPU IDs in prog profile
    https://git.kernel.org/bpf/bpf-next/c/edc071d7b3aa

You are awesome, thank you!
-- 
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