Re: [PATCH bpf-next v2 3/4] selftests/bpf: Fix ringbuf/ringbuf_write test failure with arm64 64KB page size

[Yonghong Song <yonghong.song@linux.dev>]

On 6/6/25 1:53 PM, Alexei Starovoitov wrote:
> On Fri, Jun 6, 2025 at 10:42 AM Yonghong Song <yonghong.song@linux.dev> wrote:
>> The ringbuf max_entries must be PAGE_ALIGNED. See kernel function
>> ringbuf_map_alloc(). So for arm64 64KB page size, adjust max_entries
>> properly.
>>
>> Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
>> ---
>>   tools/testing/selftests/bpf/prog_tests/ringbuf.c       | 5 +++--
>>   tools/testing/selftests/bpf/progs/test_ringbuf_write.c | 5 +++--
>>   2 files changed, 6 insertions(+), 4 deletions(-)
>>
>> diff --git a/tools/testing/selftests/bpf/prog_tests/ringbuf.c b/tools/testing/selftests/bpf/prog_tests/ringbuf.c
>> index da430df45aa4..89fd3401a23e 100644
>> --- a/tools/testing/selftests/bpf/prog_tests/ringbuf.c
>> +++ b/tools/testing/selftests/bpf/prog_tests/ringbuf.c
>> @@ -97,7 +97,8 @@ static void ringbuf_write_subtest(void)
>>          if (!ASSERT_OK_PTR(skel, "skel_open"))
>>                  return;
>>
>> -       skel->maps.ringbuf.max_entries = 0x4000;
>> +       skel->maps.ringbuf.max_entries = 4 * page_size;
>> +       skel->rodata->reserve_size = 3 * page_size;
>>
>>          err = test_ringbuf_write_lskel__load(skel);
>>          if (!ASSERT_OK(err, "skel_load"))
>> @@ -108,7 +109,7 @@ static void ringbuf_write_subtest(void)
>>          mmap_ptr = mmap(NULL, page_size, PROT_READ | PROT_WRITE, MAP_SHARED, rb_fd, 0);
>>          if (!ASSERT_OK_PTR(mmap_ptr, "rw_cons_pos"))
>>                  goto cleanup;
>> -       *mmap_ptr = 0x3000;
>> +       *mmap_ptr = 3 * page_size;
>>          ASSERT_OK(munmap(mmap_ptr, page_size), "unmap_rw");
>>
>>          skel->bss->pid = getpid();
>> diff --git a/tools/testing/selftests/bpf/progs/test_ringbuf_write.c b/tools/testing/selftests/bpf/progs/test_ringbuf_write.c
>> index 350513c0e4c9..9acef7afbe8a 100644
>> --- a/tools/testing/selftests/bpf/progs/test_ringbuf_write.c
>> +++ b/tools/testing/selftests/bpf/progs/test_ringbuf_write.c
>> @@ -12,6 +12,7 @@ struct {
>>
>>   /* inputs */
>>   int pid = 0;
>> +const volatile int reserve_size = 0;
> See CI failure:
> |test_ringbuf_write.bpf.o|test_ringbuf_write|success -> failure (!!)|+0.00 % |
>
> I think it's better to init reserve_size with some reasonable
> constant to keep veristat happy.

Yes, I am aware of this and actually fixed locally already. Will send out v3 soon.

>
> pw-bot: cr