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([2001:ee0:4f0f:b1d0:3f07:f8d8:f49b:c576]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2adfb6a03fbsm226689635ad.43.2026.03.03.06.44.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Mar 2026 06:45:00 -0800 (PST) Message-ID: <935c773d-e6d5-4445-b5e3-ed8daf60001c@gmail.com> Date: Tue, 3 Mar 2026 21:44:53 +0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next v2] virtio-net: xsk: Support wakeup on RX side To: "Michael S. Tsirkin" Cc: netdev@vger.kernel.org, Jason Wang , Xuan Zhuo , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , virtualization@lists.linux.dev, linux-kernel@vger.kernel.org References: <20260302164158.4394-1-minhquangbui99@gmail.com> <20260302135032-mutt-send-email-mst@kernel.org> Content-Language: en-US From: Bui Quang Minh In-Reply-To: <20260302135032-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 3/3/26 01:53, Michael S. Tsirkin wrote: > 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. I'll update the comment of try_fill_recv function. Thanks, Quang Minh. > > > >> + } >> + >> 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