When application runs in zero copy busy poll mode and does not receive a single packet but only sends them, it is currently impossible to get into napi_busy_loop() as napi_id is only marked on Rx side in xsk_rcv_check(). In there, napi_id is being taken from xdp_rxq_info carried by xdp_buff. From Tx perspective, we do not have access to it. What we have handy is the xsk pool. Xsk pool works on a pool of internal xdp_buff wrappers called xdp_buff_xsk. AF_XDP ZC enabled drivers call xp_set_rxq_info() so each of xdp_buff_xsk has a valid pointer to xdp_rxq_info of underlying queue. Therefore, on Tx side, napi_id can be pulled from xs->pool->heads[0].xdp.rxq->napi_id. Do this only for sockets working in ZC mode as otherwise rxq pointers would not be initialized. Fixes: a0731952d9cd ("xsk: Add busy-poll support for {recv,send}msg()") Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@xxxxxxxxx> --- net/xdp/xsk.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c index 19ac872a6624..eafd512d38b1 100644 --- a/net/xdp/xsk.c +++ b/net/xdp/xsk.c @@ -637,8 +637,11 @@ static int __xsk_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len if (unlikely(need_wait)) return -EOPNOTSUPP; - if (sk_can_busy_loop(sk)) + if (sk_can_busy_loop(sk)) { + if (xs->zc) + __sk_mark_napi_id_once(sk, xs->pool->heads[0].xdp.rxq->napi_id); sk_busy_loop(sk, 1); /* only support non-blocking sockets */ + } if (xs->zc && xsk_no_wakeup(sk)) return 0; -- 2.27.0