Re: [RFC PATCH bpf-next v2 3/3] selftests/bpf: Add case to test BPF_F_CPU

[Leon Hwang <leon.hwang@linux.dev>]

On 2025/7/12 02:11, Andrii Nakryiko wrote:
> On Mon, Jul 7, 2025 at 9:04 AM Leon Hwang <leon.hwang@linux.dev> wrote:
>>
>> This patch adds test coverage for the new BPF_F_CPU flag support in
>> percpu_array maps. The following APIs are exercised:
>>
>> * bpf_map_update_batch()
>> * bpf_map_lookup_batch()
>> * bpf_map_update_elem_opts()
>> * bpf_map__update_elem_opts()
>> * bpf_map_lookup_elem_opts()
>> * bpf_map__lookup_elem_opts()
>>
>> cd tools/testing/selftests/bpf/
>> ./test_progs -t percpu_alloc/cpu_flag_tests
>> 253/13  percpu_alloc/cpu_flag_tests:OK
>> 253     percpu_alloc:OK
>> Summary: 1/13 PASSED, 0 SKIPPED, 0 FAILED
>>
>> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
>> ---
>>  .../selftests/bpf/prog_tests/percpu_alloc.c   | 170 ++++++++++++++++++
>>  .../selftests/bpf/progs/percpu_array_flag.c   |  24 +++
>>  2 files changed, 194 insertions(+)
>>  create mode 100644 tools/testing/selftests/bpf/progs/percpu_array_flag.c
>>
>> diff --git a/tools/testing/selftests/bpf/prog_tests/percpu_alloc.c b/tools/testing/selftests/bpf/prog_tests/percpu_alloc.c
>> index 343da65864d6..6f0d0e6dc76a 100644
>> --- a/tools/testing/selftests/bpf/prog_tests/percpu_alloc.c
>> +++ b/tools/testing/selftests/bpf/prog_tests/percpu_alloc.c
>> @@ -3,6 +3,7 @@
>>  #include "percpu_alloc_array.skel.h"
>>  #include "percpu_alloc_cgrp_local_storage.skel.h"
>>  #include "percpu_alloc_fail.skel.h"
>> +#include "percpu_array_flag.skel.h"
>>
>>  static void test_array(void)
>>  {
>> @@ -115,6 +116,173 @@ static void test_failure(void) {
>>         RUN_TESTS(percpu_alloc_fail);
>>  }
>>
>> +static void test_cpu_flag(void)
>> +{
>> +       int map_fd, *keys = NULL, value_size, cpu, i, j, nr_cpus, err;
>> +       size_t key_sz = sizeof(int), value_sz = sizeof(u64);
>> +       struct percpu_array_flag *skel;
>> +       u64 batch = 0, *values = NULL;
>> +       const u64 value = 0xDEADC0DE;
>> +       u32 count, max_entries;
>> +       struct bpf_map *map;
>> +       LIBBPF_OPTS(bpf_map_lookup_elem_opts, lookup_opts,
>> +                   .flags = BPF_F_CPU,
>> +                   .cpu = 0,
>> +       );
>> +       LIBBPF_OPTS(bpf_map_update_elem_opts, update_opts,
>> +                   .flags = BPF_F_CPU,
>> +                   .cpu = 0,
>> +       );
>> +       LIBBPF_OPTS(bpf_map_batch_opts, batch_opts,
>> +                   .elem_flags = BPF_F_CPU,
>> +                   .flags = 0,
>> +       );
>> +
>> +       nr_cpus = libbpf_num_possible_cpus();
>> +       if (!ASSERT_GT(nr_cpus, 0, "libbpf_num_possible_cpus"))
>> +               return;
>> +
>> +       skel = percpu_array_flag__open_and_load();
>> +       if (!ASSERT_OK_PTR(skel, "percpu_array_flag__open_and_load"))
>> +               return;
>> +
>> +       map = skel->maps.percpu;
>> +       map_fd = bpf_map__fd(map);
>> +       max_entries = bpf_map__max_entries(map);
>> +
>> +       value_size = value_sz * nr_cpus;
>> +       values = calloc(max_entries, value_size);
>> +       keys = calloc(max_entries, key_sz);
>> +       if (!ASSERT_FALSE(!keys || !values, "calloc keys and values"))
> 
> ASSERT_xxx are meant to be meaningful in the case that some condition
> fails, so using generic ASSERT_FALSE with some complicated condition
> is defeating that purpose. Use two separate ASSERT_OK_PTR checks
> instead.
> 

Got it.

Thanks,
Leon