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xsk: Mark napi_id on sendmsg()

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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@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Magnus Karlsson <magnus.karlsson@intel.com>
Link: https://lore.kernel.org/bpf/20220707130842.49408-1-maciej.fijalkowski@intel.com
This commit is contained in:
Maciej Fijalkowski 2022-07-07 15:08:42 +02:00 committed by Daniel Borkmann
parent 33f32e5072
commit ca2e1a6270
2 changed files with 18 additions and 1 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

14
include/net/xdp_sock_drv.h
View file

@ -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)
{

5
net/xdp/xsk.c
View file

@ -639,8 +639,11 @@ 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;