When application runs in 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. Hide this pointer chase under
helper function, xsk_pool_get_napi_id().
Do this only for sockets working in ZC mode as otherwise rxq pointers
would not be initialized.
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@xxxxxxxxx>
---
v2:
* target bpf-next instead of bpf and don't treat it as fix (Bjorn)
* hide pointer chasing under helper function (Bjorn)
include/net/xdp_sock_drv.h | 14 ++++++++++++++
net/xdp/xsk.c | 5 ++++-
2 files changed, 18 insertions(+), 1 deletion(-)
diff --git a/include/net/xdp_sock_drv.h b/include/net/xdp_sock_drv.h
index 4aa031849668..4277b0dcee05 100644
--- a/include/net/xdp_sock_drv.h
+++ b/include/net/xdp_sock_drv.h
@@ -44,6 +44,15 @@ static inline void xsk_pool_set_rxq_info(struct xsk_buff_pool *pool,
xp_set_rxq_info(pool, rxq);
}
+static inline unsigned int xsk_pool_get_napi_id(struct xsk_buff_pool *pool)
+{
+#ifdef CONFIG_NET_RX_BUSY_POLL
+ return pool->heads[0].xdp.rxq->napi_id;
+#else
+ return 0;
+#endif
+}
+
static inline void xsk_pool_dma_unmap(struct xsk_buff_pool *pool,
unsigned long attrs)
{
@@ -198,6 +207,11 @@ static inline void xsk_pool_set_rxq_info(struct xsk_buff_pool *pool,
{
}
+static inline unsigned int xsk_pool_get_napi_id(struct xsk_buff_pool *pool)
+{
+ return 0;
+}
+
static inline void xsk_pool_dma_unmap(struct xsk_buff_pool *pool,
unsigned long attrs)
{
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 19ac872a6624..86a97da7e50b 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, xsk_pool_get_napi_id(xs->pool));
sk_busy_loop(sk, 1); /* only support non-blocking sockets */
+ }
if (xs->zc && xsk_no_wakeup(sk))
return 0;
--
2.27.0
