selftests/xsk: Make batch size variable

Convert the constant BATCH_SIZE into a variable named batch_size to allow
dynamic modification at runtime. This is required for the forthcoming
changes to support testing different hardware ring sizes.

While running these tests, a bug was identified when the batch size is
roughly the same as the NIC ring size. This has now been addressed by
Maciej's fix in commit 913eda2b ("i40e: xsk: remove count_mask").
Signed-off-by: Tushar Vyavahare <tushar.vyavahare@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Magnus Karlsson <magnus.karlsson@intel.com>
Link: https://lore.kernel.org/bpf/20240402114529.545475-3-tushar.vyavahare@intel.com

tools/testing/selftests/bpf/xskxceiver.c

@@ -239,7 +239,7 @@ static void enable_busy_poll(struct xsk_socket_info *xsk)
 		       (void *)&sock_opt, sizeof(sock_opt)) < 0)
 		exit_with_error(errno);
 
-	sock_opt = BATCH_SIZE;
+	sock_opt = xsk->batch_size;
 	if (setsockopt(xsk_socket__fd(xsk->xsk), SOL_SOCKET, SO_BUSY_POLL_BUDGET,
 		       (void *)&sock_opt, sizeof(sock_opt)) < 0)
 		exit_with_error(errno);
@@ -439,6 +439,7 @@ static void __test_spec_init(struct test_spec *test, struct ifobject *ifobj_tx,
 		for (j = 0; j < MAX_SOCKETS; j++) {
 			memset(&ifobj->xsk_arr[j], 0, sizeof(ifobj->xsk_arr[j]));
 			ifobj->xsk_arr[j].rxqsize = XSK_RING_CONS__DEFAULT_NUM_DESCS;
+			ifobj->xsk_arr[j].batch_size = DEFAULT_BATCH_SIZE;
 			if (i == 0)
 				ifobj->xsk_arr[j].pkt_stream = test->tx_pkt_stream_default;
 			else
@@ -1087,7 +1088,7 @@ static int __receive_pkts(struct test_spec *test, struct xsk_socket_info *xsk)
 			return TEST_CONTINUE;
 	}
 
-	rcvd = xsk_ring_cons__peek(&xsk->rx, BATCH_SIZE, &idx_rx);
+	rcvd = xsk_ring_cons__peek(&xsk->rx, xsk->batch_size, &idx_rx);
 	if (!rcvd)
 		return TEST_CONTINUE;
 
@@ -1239,7 +1240,8 @@ static int __send_pkts(struct ifobject *ifobject, struct xsk_socket_info *xsk, b
 
 	buffer_len = pkt_get_buffer_len(umem, pkt_stream->max_pkt_len);
 	/* pkts_in_flight might be negative if many invalid packets are sent */
-	if (pkts_in_flight >= (int)((umem_size(umem) - BATCH_SIZE * buffer_len) / buffer_len)) {
+	if (pkts_in_flight >= (int)((umem_size(umem) - xsk->batch_size * buffer_len) /
+	    buffer_len)) {
 		ret = kick_tx(xsk);
 		if (ret)
 			return TEST_FAILURE;
@@ -1249,7 +1251,7 @@ static int __send_pkts(struct ifobject *ifobject, struct xsk_socket_info *xsk, b
 	fds.fd = xsk_socket__fd(xsk->xsk);
 	fds.events = POLLOUT;
 
-	while (xsk_ring_prod__reserve(&xsk->tx, BATCH_SIZE, &idx) < BATCH_SIZE) {
+	while (xsk_ring_prod__reserve(&xsk->tx, xsk->batch_size, &idx) < xsk->batch_size) {
 		if (use_poll) {
 			ret = poll(&fds, 1, POLL_TMOUT);
 			if (timeout) {
@@ -1269,10 +1271,10 @@ static int __send_pkts(struct ifobject *ifobject, struct xsk_socket_info *xsk, b
 			}
 		}
 
-		complete_pkts(xsk, BATCH_SIZE);
+		complete_pkts(xsk, xsk->batch_size);
 	}
 
-	for (i = 0; i < BATCH_SIZE; i++) {
+	for (i = 0; i < xsk->batch_size; i++) {
 		struct pkt *pkt = pkt_stream_get_next_tx_pkt(pkt_stream);
 		u32 nb_frags_left, nb_frags, bytes_written = 0;
 
@@ -1280,9 +1282,9 @@ static int __send_pkts(struct ifobject *ifobject, struct xsk_socket_info *xsk, b
 			break;
 
 		nb_frags = pkt_nb_frags(umem->frame_size, pkt_stream, pkt);
-		if (nb_frags > BATCH_SIZE - i) {
+		if (nb_frags > xsk->batch_size - i) {
 			pkt_stream_cancel(pkt_stream);
-			xsk_ring_prod__cancel(&xsk->tx, BATCH_SIZE - i);
+			xsk_ring_prod__cancel(&xsk->tx, xsk->batch_size - i);
 			break;
 		}
 		nb_frags_left = nb_frags;
@@ -1370,7 +1372,7 @@ static int wait_for_tx_completion(struct xsk_socket_info *xsk)
 			return TEST_FAILURE;
 		}
 
-		complete_pkts(xsk, BATCH_SIZE);
+		complete_pkts(xsk, xsk->batch_size);
 	}
 
 	return TEST_PASS;

tools/testing/selftests/bpf/xskxceiver.h

@@ -44,7 +44,7 @@
 #define MAX_ETH_JUMBO_SIZE 9000
 #define USLEEP_MAX 10000
 #define SOCK_RECONF_CTR 10
-#define BATCH_SIZE 64
+#define DEFAULT_BATCH_SIZE 64
 #define POLL_TMOUT 1000
 #define THREAD_TMOUT 3
 #define DEFAULT_PKT_CNT (4 * 1024)
@@ -91,6 +91,7 @@ struct xsk_socket_info {
 	struct pkt_stream *pkt_stream;
 	u32 outstanding_tx;
 	u32 rxqsize;
+	u32 batch_size;
 	u8 dst_mac[ETH_ALEN];
 	u8 src_mac[ETH_ALEN];
 };