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[80.230.79.166]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-483c3b44207sm315022535e9.7.2026.03.02.10.53.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Mar 2026 10:53:11 -0800 (PST) Date: Mon, 2 Mar 2026 13:53:08 -0500 From: "Michael S. Tsirkin" To: Bui Quang Minh Cc: netdev@vger.kernel.org, Jason Wang , Xuan Zhuo , Eugenio =?iso-8859-1?Q?P=E9rez?= , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , virtualization@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next v2] virtio-net: xsk: Support wakeup on RX side Message-ID: <20260302135032-mutt-send-email-mst@kernel.org> References: <20260302164158.4394-1-minhquangbui99@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260302164158.4394-1-minhquangbui99@gmail.com> On Mon, Mar 02, 2026 at 11:41:58PM +0700, Bui Quang Minh wrote: > When XDP_USE_NEED_WAKEUP is used and the fill ring is empty so no buffer > is allocated on RX side, allow RX NAPI to be descheduled. This avoids > wasting CPU cycles on polling. Users will be notified and they need to > make a wakeup call after refilling the ring. > > Signed-off-by: Bui Quang Minh > --- > Changes in v2: > - Fix the flag check in virtnet_xsk_wakeup > - Link to v1: https://lore.kernel.org/netdev/20260227150949.13089-1-minhquangbui99@gmail.com/ > --- > drivers/net/virtio_net.c | 35 +++++++++++++++++++++++++++-------- > 1 file changed, 27 insertions(+), 8 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index db88dcaefb20..3614002fc87c 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -1454,8 +1454,19 @@ static int virtnet_add_recvbuf_xsk(struct virtnet_info *vi, struct receive_queue > xsk_buffs = rq->xsk_buffs; > > num = xsk_buff_alloc_batch(pool, xsk_buffs, rq->vq->num_free); > - if (!num) > + if (!num) { > + if (xsk_uses_need_wakeup(pool)) { > + xsk_set_rx_need_wakeup(pool); > + /* Return 0 instead of -ENOMEM so that NAPI is > + * descheduled. > + */ > + return 0; With this change, try_fill_recv() can return true even though zero RX buffers were posted in need_wakeup mode, which contradicts its documentation ("Returns false if we couldn't fill entirely (OOM)"). Methinks we need to at least update the comment near try_fill_recv. > + } > + > return -ENOMEM; > + } else { > + xsk_clear_rx_need_wakeup(pool); > + } > > len = xsk_pool_get_rx_frame_size(pool) + vi->hdr_len; > > @@ -1588,20 +1599,19 @@ static bool virtnet_xsk_xmit(struct send_queue *sq, struct xsk_buff_pool *pool, > return sent; > } > > -static void xsk_wakeup(struct send_queue *sq) > +static void xsk_wakeup(struct napi_struct *napi, struct virtqueue *vq) > { > - if (napi_if_scheduled_mark_missed(&sq->napi)) > + if (napi_if_scheduled_mark_missed(napi)) > return; > > local_bh_disable(); > - virtqueue_napi_schedule(&sq->napi, sq->vq); > + virtqueue_napi_schedule(napi, vq); > local_bh_enable(); > } > > static int virtnet_xsk_wakeup(struct net_device *dev, u32 qid, u32 flag) > { > struct virtnet_info *vi = netdev_priv(dev); > - struct send_queue *sq; > > if (!netif_running(dev)) > return -ENETDOWN; > @@ -1609,9 +1619,18 @@ static int virtnet_xsk_wakeup(struct net_device *dev, u32 qid, u32 flag) > if (qid >= vi->curr_queue_pairs) > return -EINVAL; > > - sq = &vi->sq[qid]; > + if (flag & XDP_WAKEUP_TX) { > + struct send_queue *sq = &vi->sq[qid]; > + > + xsk_wakeup(&sq->napi, sq->vq); > + } > + > + if (flag & XDP_WAKEUP_RX) { > + struct receive_queue *rq = &vi->rq[qid]; > + > + xsk_wakeup(&rq->napi, rq->vq); > + } > > - xsk_wakeup(sq); > return 0; > } > > @@ -1623,7 +1642,7 @@ static void virtnet_xsk_completed(struct send_queue *sq, int num) > * wakeup the tx napi to consume the xsk tx queue, because the tx > * interrupt may not be triggered. > */ > - xsk_wakeup(sq); > + xsk_wakeup(&sq->napi, sq->vq); > } > > static int __virtnet_xdp_xmit_one(struct virtnet_info *vi, > -- > 2.43.0