Re: [PATCH bpf-next v10 8/8] selftests/bpf: Add cases to test BPF_F_CPU and BPF_F_ALL_CPUS flags

On Mon, Nov 17, 2025 at 8:22 AM Leon Hwang leon.hwang@linux.dev wrote:

Add test coverage for the new BPF_F_CPU and BPF_F_ALL_CPUS flags support in percpu maps. The following APIs are exercised:

• bpf_map_update_batch()
• bpf_map_lookup_batch()
• bpf_map_update_elem()
• bpf_map__update_elem()
• bpf_map_lookup_elem_flags()
• bpf_map__lookup_elem()

Add tests to verify that array and hash maps do not support BPF_F_CPU and BPF_F_ALL_CPUS flags.

Signed-off-by: Leon Hwang leon.hwang@linux.dev

.../selftests/bpf/prog_tests/percpu_alloc.c | 312 ++++++++++++++++++ .../selftests/bpf/progs/percpu_alloc_array.c | 32 ++ 2 files changed, 344 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/percpu_alloc.c b/tools/testing/selftests/bpf/prog_tests/percpu_alloc.c index 343da65864d6d..b9c3f5f6cd9c3 100644 --- a/tools/testing/selftests/bpf/prog_tests/percpu_alloc.c +++ b/tools/testing/selftests/bpf/prog_tests/percpu_alloc.c @@ -1,5 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 #include <test_progs.h> +#include "cgroup_helpers.h" #include "percpu_alloc_array.skel.h" #include "percpu_alloc_cgrp_local_storage.skel.h" #include "percpu_alloc_fail.skel.h" @@ -115,6 +116,305 @@ static void test_failure(void) { RUN_TESTS(percpu_alloc_fail); }

+static void test_percpu_map_op_cpu_flag(struct bpf_map *map, void *keys, size_t key_sz,

•                                   u32 max_entries, bool test_batch)
  

+{

•   size_t value_sz = sizeof(u32), value_sz_cpus, value_sz_total;
  

•   u32 *values = NULL, *values_percpu = NULL;
  

•   int i, j, cpu, map_fd, nr_cpus, err;
  

•   const u32 value = 0xDEADC0DE;
  

•   u32 count = max_entries, v;
  

•   u64 batch = 0, flags;
  

•   void *values_row;
  

•   LIBBPF_OPTS(bpf_map_batch_opts, batch_opts);
  

•   nr_cpus = libbpf_num_possible_cpus();
  

•   if (!ASSERT_GT(nr_cpus, 0, "libbpf_num_possible_cpus"))
  

•           return;
  

•   value_sz_cpus = value_sz * nr_cpus;
  

•   values = calloc(max_entries, value_sz_cpus);
  

•   if (!ASSERT_OK_PTR(values, "calloc values"))
  

•           return;
  

•   values_percpu = calloc(max_entries, roundup(value_sz, 8) * nr_cpus);
  

•   if (!ASSERT_OK_PTR(values_percpu, "calloc values_percpu")) {
  

•           free(values);
  

•           return;
  

•   }
  

•   value_sz_total = value_sz_cpus * max_entries;
  

•   memset(values, 0, value_sz_total);
  

•   map_fd = bpf_map__fd(map);
  

•   flags = BPF_F_CPU | BPF_F_ALL_CPUS;
  

•   err = bpf_map_lookup_elem_flags(map_fd, keys, values, flags);
  

•   if (!ASSERT_ERR(err, "bpf_map_lookup_elem_flags cpu|all_cpus"))
  

•           goto out;
  

•   err = bpf_map_update_elem(map_fd, keys, values, flags);
  

•   if (!ASSERT_ERR(err, "bpf_map_update_elem cpu|all_cpus"))
  

•           goto out;
  

•   flags = BPF_F_ALL_CPUS;
  

•   err = bpf_map_lookup_elem_flags(map_fd, keys, values, flags);
  

•   if (!ASSERT_ERR(err, "bpf_map_lookup_elem_flags all_cpus"))
  

•           goto out;
  

•   flags = BPF_F_LOCK | BPF_F_CPU;
  

•   err = bpf_map_lookup_elem_flags(map_fd, keys, values, flags);
  

•   if (!ASSERT_ERR(err, "bpf_map_lookup_elem_flags BPF_F_LOCK"))
  

•           goto out;
  

•   flags = BPF_F_LOCK | BPF_F_ALL_CPUS;
  

•   err = bpf_map_update_elem(map_fd, keys, values, flags);
  

•   if (!ASSERT_ERR(err, "bpf_map_update_elem BPF_F_LOCK"))
  

•           goto out;
  

•   flags = (u64)nr_cpus << 32 | BPF_F_CPU;
  

•   err = bpf_map_update_elem(map_fd, keys, values, flags);
  

•   if (!ASSERT_EQ(err, -ERANGE, "bpf_map_update_elem -ERANGE"))
  

•           goto out;
  

•   err = bpf_map__update_elem(map, keys, key_sz, values, value_sz, flags);
  

•   if (!ASSERT_EQ(err, -ERANGE, "bpf_map__update_elem -ERANGE"))
  

•           goto out;
  

•   err = bpf_map_lookup_elem_flags(map_fd, keys, values, flags);
  

•   if (!ASSERT_EQ(err, -ERANGE, "bpf_map_lookup_elem_flags -ERANGE"))
  

•           goto out;
  

•   err = bpf_map__lookup_elem(map, keys, key_sz, values, value_sz, flags);
  

•   if (!ASSERT_EQ(err, -ERANGE, "bpf_map__lookup_elem -ERANGE"))
  

•           goto out;
  

•   for (cpu = 0; cpu < nr_cpus; cpu++) {
  

•           /* clear value on all cpus */
  

•           values[0] = 0;
  

•           flags = BPF_F_ALL_CPUS;
  

•           for (i = 0; i < max_entries; i++) {
  

•                   err = bpf_map__update_elem(map, keys + i * key_sz, key_sz, values,
  

•                                              value_sz, flags);
  

•                   if (!ASSERT_OK(err, "bpf_map__update_elem all_cpus"))
  

•                           goto out;
  

•           }
  

•           /* update value on specified cpu */
  

•           for (i = 0; i < max_entries; i++) {
  

•                   values[0] = value;
  

•                   flags = (u64)cpu << 32 | BPF_F_CPU;
  

•                   err = bpf_map__update_elem(map, keys + i * key_sz, key_sz, values,
  

•                                              value_sz, flags);
  

•                   if (!ASSERT_OK(err, "bpf_map__update_elem specified cpu"))
  

•                           goto out;
  

•                   /* lookup then check value on CPUs */
  

•                   for (j = 0; j < nr_cpus; j++) {
  

•                           flags = (u64)j << 32 | BPF_F_CPU;
  

•                           err = bpf_map__lookup_elem(map, keys + i * key_sz, key_sz, values,
  

•                                                      value_sz, flags);
  

•                           if (!ASSERT_OK(err, "bpf_map__lookup_elem specified cpu"))
  

•                                   goto out;
  

•                           if (!ASSERT_EQ(values[0], j != cpu ? 0 : value,
  

•                                          "bpf_map__lookup_elem value on specified cpu"))
  

•                                   goto out;
  

I was about to apply it, but noticed that the test is unstable. It fails 1 out of 10 for me in the above line. test_percpu_map_op_cpu_flag:PASS:bpf_map_lookup_batch value on specified cpu 0 nsec test_percpu_map_op_cpu_flag:FAIL:bpf_map_lookup_batch value on specified cpu unexpected bpf_map_lookup_batch value on specified cpu: actual 0 != expected 3735929054 #261/15 percpu_alloc/cpu_flag_lru_percpu_hash:FAIL #261 percpu_alloc:FAIL

Please investigate what is going on.

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