Re: [PATCH net-next v6 2/2] selftests/bpf: add a new test to check the consumer update case

[Maciej Fijalkowski <maciej.fijalkowski@intel.com>]

On Thu, Jul 03, 2025 at 10:17:12PM +0800, Jason Xing wrote:
> From: Jason Xing <kernelxing@tencent.com>
> 
> The subtest sends 33 packets at one time on purpose to see if xsk
> exitting __xsk_generic_xmit() updates the global consumer of tx queue
> when reaching the max loop (max_tx_budget, 32 by default). The number 33
> can avoid xskq_cons_peek_desc() updates the consumer when it's about to
> quit sending, to accurately check if the issue that the first patch
> resolves remains. The new case will not check this issue in zero copy
> mode.
> 
> Signed-off-by: Jason Xing <kernelxing@tencent.com>

Acked-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>

> ---
> v6
> Link: https://lore.kernel.org/all/20250702112815.50746-1-kerneljasonxing@gmail.com/
> 1. filter out and skip TEST_MODE_ZC test.
> 
> v5
> Link: https://lore.kernel.org/all/20250627085745.53173-1-kerneljasonxing@gmail.com/
> 1. use the initial approach to add a new testcase
> 2. add a new flag 'check_consumer' to see if the check is needed
> ---
>  tools/testing/selftests/bpf/xskxceiver.c | 56 +++++++++++++++++++++++-
>  tools/testing/selftests/bpf/xskxceiver.h |  1 +
>  2 files changed, 56 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/bpf/xskxceiver.c b/tools/testing/selftests/bpf/xskxceiver.c
> index 0ced4026ee44..a29de0713f19 100644
> --- a/tools/testing/selftests/bpf/xskxceiver.c
> +++ b/tools/testing/selftests/bpf/xskxceiver.c
> @@ -109,6 +109,8 @@
>  
>  #include <network_helpers.h>
>  
> +#define MAX_TX_BUDGET_DEFAULT 32
> +
>  static bool opt_verbose;
>  static bool opt_print_tests;
>  static enum test_mode opt_mode = TEST_MODE_ALL;
> @@ -1091,11 +1093,45 @@ static bool is_pkt_valid(struct pkt *pkt, void *buffer, u64 addr, u32 len)
>  	return true;
>  }
>  
> +static u32 load_value(u32 *counter)
> +{
> +	return __atomic_load_n(counter, __ATOMIC_ACQUIRE);
> +}
> +
> +static bool kick_tx_with_check(struct xsk_socket_info *xsk, int *ret)
> +{
> +	u32 max_budget = MAX_TX_BUDGET_DEFAULT;
> +	u32 cons, ready_to_send;
> +	int delta;
> +
> +	cons = load_value(xsk->tx.consumer);
> +	ready_to_send = load_value(xsk->tx.producer) - cons;
> +	*ret = sendto(xsk_socket__fd(xsk->xsk), NULL, 0, MSG_DONTWAIT, NULL, 0);
> +
> +	delta = load_value(xsk->tx.consumer) - cons;
> +	/* By default, xsk should consume exact @max_budget descs at one
> +	 * send in this case where hitting the max budget limit in while
> +	 * loop is triggered in __xsk_generic_xmit(). Please make sure that
> +	 * the number of descs to be sent is larger than @max_budget, or
> +	 * else the tx.consumer will be updated in xskq_cons_peek_desc()
> +	 * in time which hides the issue we try to verify.
> +	 */
> +	if (ready_to_send > max_budget && delta != max_budget)
> +		return false;
> +
> +	return true;
> +}
> +
>  static int kick_tx(struct xsk_socket_info *xsk)
>  {
>  	int ret;
>  
> -	ret = sendto(xsk_socket__fd(xsk->xsk), NULL, 0, MSG_DONTWAIT, NULL, 0);
> +	if (xsk->check_consumer) {
> +		if (!kick_tx_with_check(xsk, &ret))
> +			return TEST_FAILURE;
> +	} else {
> +		ret = sendto(xsk_socket__fd(xsk->xsk), NULL, 0, MSG_DONTWAIT, NULL, 0);
> +	}
>  	if (ret >= 0)
>  		return TEST_PASS;
>  	if (errno == ENOBUFS || errno == EAGAIN || errno == EBUSY || errno == ENETDOWN) {
> @@ -2613,6 +2649,23 @@ static int testapp_adjust_tail_grow_mb(struct test_spec *test)
>  				   XSK_UMEM__LARGE_FRAME_SIZE * 2);
>  }
>  
> +static int testapp_tx_queue_consumer(struct test_spec *test)
> +{
> +	int nr_packets;
> +
> +	if (test->mode == TEST_MODE_ZC) {
> +		ksft_test_result_skip("Can not run TX_QUEUE_CONSUMER test for ZC mode\n");
> +		return TEST_SKIP;
> +	}
> +
> +	nr_packets = MAX_TX_BUDGET_DEFAULT + 1;
> +	pkt_stream_replace(test, nr_packets, MIN_PKT_SIZE);
> +	test->ifobj_tx->xsk->batch_size = nr_packets;
> +	test->ifobj_tx->xsk->check_consumer = true;
> +
> +	return testapp_validate_traffic(test);
> +}
> +
>  static void run_pkt_test(struct test_spec *test)
>  {
>  	int ret;
> @@ -2723,6 +2776,7 @@ static const struct test_spec tests[] = {
>  	{.name = "XDP_ADJUST_TAIL_SHRINK_MULTI_BUFF", .test_func = testapp_adjust_tail_shrink_mb},
>  	{.name = "XDP_ADJUST_TAIL_GROW", .test_func = testapp_adjust_tail_grow},
>  	{.name = "XDP_ADJUST_TAIL_GROW_MULTI_BUFF", .test_func = testapp_adjust_tail_grow_mb},
> +	{.name = "TX_QUEUE_CONSUMER", .test_func = testapp_tx_queue_consumer},
>  	};
>  
>  static void print_tests(void)
> diff --git a/tools/testing/selftests/bpf/xskxceiver.h b/tools/testing/selftests/bpf/xskxceiver.h
> index 67fc44b2813b..4df3a5d329ac 100644
> --- a/tools/testing/selftests/bpf/xskxceiver.h
> +++ b/tools/testing/selftests/bpf/xskxceiver.h
> @@ -95,6 +95,7 @@ struct xsk_socket_info {
>  	u32 batch_size;
>  	u8 dst_mac[ETH_ALEN];
>  	u8 src_mac[ETH_ALEN];
> +	bool check_consumer;
>  };
>  
>  struct pkt {
> -- 
> 2.41.3
>