Re: [PATCH bpf-next 2/2] selftests/bpf: Fix xdp_pull_data failure with 64K page

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

On 1/22/26 3:02 AM, Alan Maguire wrote:
> On 20/01/2026 21:09, Yonghong Song wrote:
>> If the argument 'pull_len' of run_test() is 'PULL_MAX' or
>> 'PULL_MAX | PULL_PLUS_ONE', the eventual pull_len size
>> will close to the page size. On arm64 systems with 64K pages,
>> the pull_len size will be close to 64K. But the existing buffer
>> will be close to 9000 which is not enough to pull.
>>
>> So for 64K page size and selective run_tests(), increase
>> buff size from 9000 to 90000 to ensure enough buffer space
>> to pull.
>>
>> Cc: Amery Hung <ameryhung@gmail.com>
>> Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
> Tested-by: Alan Maguire <alan.maguire@oracle.com>
>
> one optional suggestion below..
>
>
>> ---
>>   .../selftests/bpf/prog_tests/xdp_pull_data.c     | 16 +++++++++++-----
>>   1 file changed, 11 insertions(+), 5 deletions(-)
>>
>> diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_pull_data.c b/tools/testing/selftests/bpf/prog_tests/xdp_pull_data.c
>> index efa350d04ec5..32ac99406d28 100644
>> --- a/tools/testing/selftests/bpf/prog_tests/xdp_pull_data.c
>> +++ b/tools/testing/selftests/bpf/prog_tests/xdp_pull_data.c
>> @@ -8,6 +8,7 @@
>>   #define PULL_PLUS_ONE	(1 << 30)
>>   
>>   #define XDP_PACKET_HEADROOM 256
>> +#define PAGE_SIZE_64K 65536
>>   
>>   /* Find headroom and tailroom occupied by struct xdp_frame and struct
>>    * skb_shared_info so that we can calculate the maximum pull lengths for
>> @@ -114,12 +115,17 @@ static void test_xdp_pull_data_basic(void)
>>   {
>>   	u32 pg_sz, max_meta_len, max_data_len;
>>   	struct test_xdp_pull_data *skel;
>> +	int buff_len;
>>   
>>   	skel = test_xdp_pull_data__open_and_load();
>>   	if (!ASSERT_OK_PTR(skel, "test_xdp_pull_data__open_and_load"))
>>   		return;
>>   
>>   	pg_sz = sysconf(_SC_PAGE_SIZE);
>> +	if (pg_sz == PAGE_SIZE_64K)
>> +		buff_len = 90000;
>> +	else
>> +		buff_len = 9000;
>>   
> nit: should we generalize here and just use 1.5 * pg_sz; i.e.
>
> 	buff_len = pg_sz + (pg_sz/2);
>
> that would eliminate the need for the 64k page size #define.

Thanks for suggestion! This indeed simpler. Will make the change in v2.

>
>>   	if (find_xdp_sizes(skel, pg_sz))
>>   		goto out;
>> @@ -140,13 +146,13 @@ static void test_xdp_pull_data_basic(void)
>>   	run_test(skel, XDP_PASS, pg_sz, 9000, 0, 1025, 1025);
>>   
>>   	/* multi-buf pkt, empty linear data area, pull requires memmove */
>> -	run_test(skel, XDP_PASS, pg_sz, 9000, 0, 0, PULL_MAX);
>> +	run_test(skel, XDP_PASS, pg_sz, buff_len, 0, 0, PULL_MAX);
>>   
>>   	/* multi-buf pkt, no headroom */
>> -	run_test(skel, XDP_PASS, pg_sz, 9000, max_meta_len, 1024, PULL_MAX);
>> +	run_test(skel, XDP_PASS, pg_sz, buff_len, max_meta_len, 1024, PULL_MAX);
>>   
>>   	/* multi-buf pkt, no tailroom, pull requires memmove */
>> -	run_test(skel, XDP_PASS, pg_sz, 9000, 0, max_data_len, PULL_MAX);
>> +	run_test(skel, XDP_PASS, pg_sz, buff_len, 0, max_data_len, PULL_MAX);
>>   
>>   	/* Test cases with invalid pull length */
>>   
>> @@ -154,7 +160,7 @@ static void test_xdp_pull_data_basic(void)
>>   	run_test(skel, XDP_DROP, pg_sz, 2048, 0, 2048, 2049);
>>   
>>   	/* multi-buf pkt with no space left in linear data area */
>> -	run_test(skel, XDP_DROP, pg_sz, 9000, max_meta_len, max_data_len,
>> +	run_test(skel, XDP_DROP, pg_sz, buff_len, max_meta_len, max_data_len,
>>   		 PULL_MAX | PULL_PLUS_ONE);
>>   
>>   	/* multi-buf pkt, empty linear data area */
>> @@ -165,7 +171,7 @@ static void test_xdp_pull_data_basic(void)
>>   		 PULL_MAX | PULL_PLUS_ONE);
>>   
>>   	/* multi-buf pkt, no tailroom */
>> -	run_test(skel, XDP_DROP, pg_sz, 9000, 0, max_data_len,
>> +	run_test(skel, XDP_DROP, pg_sz, buff_len, 0, max_data_len,
>>   		 PULL_MAX | PULL_PLUS_ONE);
>>   
>>   out: