Re: [PATCH net-next 0/3] xsk: support tx napi busy_poll

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

On Thu, Jun 11, 2026 at 03:12:39PM +0800, menglong8.dong@gmail.com wrote:
> From: Menglong Dong <dongml2@chinatelecom.cn>
> 
> For now, we use sk_busy_loop() in __xsk_sendmsg() to send the data in tx
> ring. The sk_busy_loop() will poll on the target NAPI. However, for the
> nic driver that support the tx napi, such as virtio-net, it can't schedule
> the tx NAPI, but only the rx NAPI. If we enable the busy_poll for xsk and
> use virtio-net, we can't send data, as the rx NAPI in virtio-net doesn't
> handle the packet sending.

Am I reading this right that you decided to break busy-poll support for
zero-copy drivers that happen to handle transmit side from Rx NAPI context
in favor of supporting virtio-net?

> 
> Fix this by introduce the sk_tx_busy_loop(), which will poll on the tx
> NAPI if available. To get the tx NAPI from the napi_id, we add the
> "tx_napi" field to napi_struct, which is ugly :/
> 
> Another choice is to call virtnet_xsk_xmit() in virtnet_poll() too. But
> this a little contradict the design of tx NAPI.
> 
> Menglong Dong (3):
>   net: busy-poll: introduce sk_tx_busy_loop()
>   virtio_net: initialize napi.tx_napi in virtnet_alloc_queues()
>   xsk: replace sk_busy_loop with sk_tx_busy_loop in __xsk_sendmsg()
> 
>  drivers/net/virtio_net.c  |  1 +
>  include/linux/netdevice.h |  1 +
>  include/net/busy_poll.h   | 41 ++++++++++++++++++++++++++++++++++++---
>  net/core/dev.c            | 23 +++++-----------------
>  net/xdp/xsk.c             |  2 +-
>  5 files changed, 46 insertions(+), 22 deletions(-)
> 
> -- 
> 2.54.0
>