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Tsirkin" To: Xuan Zhuo Cc: Jason Wang , virtualization , netdev , "David S. Miller" , Jakub Kicinski , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , bpf@vger.kernel.org Subject: Re: [PATCH v5 17/22] virtio_net: support rx/tx queue reset Message-ID: <20220216033322-mutt-send-email-mst@kernel.org> References: <20220214081416.117695-1-xuanzhuo@linux.alibaba.com> <20220214081416.117695-18-xuanzhuo@linux.alibaba.com> <1644998173.7222953-3-xuanzhuo@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1644998173.7222953-3-xuanzhuo@linux.alibaba.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, Feb 16, 2022 at 03:56:13PM +0800, Xuan Zhuo wrote: > On Wed, 16 Feb 2022 12:14:11 +0800, Jason Wang wrote: > > On Mon, Feb 14, 2022 at 4:14 PM Xuan Zhuo wrote: > > > > > > This patch implements the reset function of the rx, tx queues. > > > > > > Based on this function, it is possible to modify the ring num of the > > > queue. And quickly recycle the buffer in the queue. > > > > > > In the process of the queue disable, in theory, as long as virtio > > > supports queue reset, there will be no exceptions. > > > > > > However, in the process of the queue enable, there may be exceptions due to > > > memory allocation. In this case, vq is not available, but we still have > > > to execute napi_enable(). Because napi_disable is similar to a lock, > > > napi_enable must be called after calling napi_disable. > > > > > > Signed-off-by: Xuan Zhuo > > > --- > > > drivers/net/virtio_net.c | 123 +++++++++++++++++++++++++++++++++++++++ > > > 1 file changed, 123 insertions(+) > > > > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > > > index 9a1445236e23..a4ffd7cdf623 100644 > > > --- a/drivers/net/virtio_net.c > > > +++ b/drivers/net/virtio_net.c > > > @@ -251,6 +251,11 @@ struct padded_vnet_hdr { > > > char padding[4]; > > > }; > > > > > > +static void virtnet_sq_free_unused_bufs(struct virtnet_info *vi, > > > + struct send_queue *sq); > > > +static void virtnet_rq_free_unused_bufs(struct virtnet_info *vi, > > > + struct receive_queue *rq); > > > + > > > static bool is_xdp_frame(void *ptr) > > > { > > > return (unsigned long)ptr & VIRTIO_XDP_FLAG; > > > @@ -1369,6 +1374,9 @@ static void virtnet_napi_enable(struct virtqueue *vq, struct napi_struct *napi) > > > { > > > napi_enable(napi); > > > > > > + if (vq->reset) > > > + return; > > > + > > > /* If all buffers were filled by other side before we napi_enabled, we > > > * won't get another interrupt, so process any outstanding packets now. > > > * Call local_bh_enable after to trigger softIRQ processing. > > > @@ -1413,6 +1421,10 @@ static void refill_work(struct work_struct *work) > > > struct receive_queue *rq = &vi->rq[i]; > > > > > > napi_disable(&rq->napi); > > > + if (rq->vq->reset) { > > > + virtnet_napi_enable(rq->vq, &rq->napi); > > > + continue; > > > + } > > > still_empty = !try_fill_recv(vi, rq, GFP_KERNEL); > > > virtnet_napi_enable(rq->vq, &rq->napi); > > > > > > @@ -1523,6 +1535,9 @@ static void virtnet_poll_cleantx(struct receive_queue *rq) > > > if (!sq->napi.weight || is_xdp_raw_buffer_queue(vi, index)) > > > return; > > > > > > + if (sq->vq->reset) > > > + return; > > > + > > > if (__netif_tx_trylock(txq)) { > > > do { > > > virtqueue_disable_cb(sq->vq); > > > @@ -1769,6 +1784,114 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) > > > return NETDEV_TX_OK; > > > } > > > > > > +static int virtnet_rx_vq_disable(struct virtnet_info *vi, > > > + struct receive_queue *rq) > > > +{ > > > + int err; > > > + > > > + napi_disable(&rq->napi); > > > + > > > + err = virtio_reset_vq(rq->vq); > > > + if (err) > > > + goto err; > > > + > > > + virtnet_rq_free_unused_bufs(vi, rq); > > > + > > > + vring_release_virtqueue(rq->vq); > > > + > > > + return 0; > > > + > > > +err: > > > + virtnet_napi_enable(rq->vq, &rq->napi); > > > + return err; > > > +} > > > + > > > +static int virtnet_tx_vq_disable(struct virtnet_info *vi, > > > + struct send_queue *sq) > > > +{ > > > + struct netdev_queue *txq; > > > + int err, qindex; > > > + > > > + qindex = sq - vi->sq; > > > + > > > + txq = netdev_get_tx_queue(vi->dev, qindex); > > > + __netif_tx_lock_bh(txq); > > > + > > > + netif_stop_subqueue(vi->dev, qindex); > > > + virtnet_napi_tx_disable(&sq->napi); > > > + > > > + err = virtio_reset_vq(sq->vq); > > > + if (err) { > > > + virtnet_napi_tx_enable(vi, sq->vq, &sq->napi); > > > + netif_start_subqueue(vi->dev, qindex); > > > + > > > + __netif_tx_unlock_bh(txq); > > > + return err; > > > + } > > > + __netif_tx_unlock_bh(txq); > > > + > > > + virtnet_sq_free_unused_bufs(vi, sq); > > > + > > > + vring_release_virtqueue(sq->vq); > > > + > > > + return 0; > > > +} > > > + > > > +static int virtnet_tx_vq_enable(struct virtnet_info *vi, struct send_queue *sq) > > > +{ > > > + int err; > > > + > > > + err = virtio_enable_resetq(sq->vq); > > > + if (!err) > > > + netif_start_subqueue(vi->dev, sq - vi->sq); > > > + > > > + virtnet_napi_tx_enable(vi, sq->vq, &sq->napi); > > > + > > > + return err; > > > +} > > > + > > > +static int virtnet_rx_vq_enable(struct virtnet_info *vi, > > > + struct receive_queue *rq) > > > +{ > > > + int err; > > > > So the API should be design in a consistent way. > > > > In rx_vq_disable() we do: > > > > reset() > > detach_unused_bufs() > > vring_release_virtqueue() > > > > here it's better to exactly the reverse > > > > vring_attach_virtqueue() // this is the helper I guess in patch 5, > > reverse of the vring_release_virtqueue() > > try_refill_recv() // reverse of the detach_unused_bufs() > > enable_reset() // reverse of the reset > > Such an api is ok > > 1. reset() > 2. detach_unused_bufs() > 3. vring_release_virtqueue() > --------------- > 4. vring_attach_virtqueue() > 5. try_refill_recv() > 6. enable_reset() > > > But if, we just want to recycle the buffer without modifying the ring num. As > you mentioned before, in the case where the ring num is not modified, we don't > have to reallocate, but can use the original vring. > > 1. reset() > 2. detach_unused_bufs() > --------------- > 3. vring_reset_virtqueue() // just reset, no reallocate > 4. try_refill_recv() > 5. enable_reset() > > Thanks. Further, can we queue the buffers instead of detach_unused_bufs and just requeue them instead of try_refill_recv? > > > > So did for the tx (no need for refill in that case). > > > > > + > > > + err = virtio_enable_resetq(rq->vq); > > > + > > > + virtnet_napi_enable(rq->vq, &rq->napi); > > > + > > > + return err; > > > +} > > > + > > > +static int virtnet_rx_vq_reset(struct virtnet_info *vi, int i) > > > +{ > > > + int err; > > > + > > > + err = virtnet_rx_vq_disable(vi, vi->rq + i); > > > + if (err) > > > + return err; > > > + > > > + err = virtnet_rx_vq_enable(vi, vi->rq + i); > > > + if (err) > > > + netdev_err(vi->dev, > > > + "enable rx reset vq fail: rx queue index: %d err: %d\n", i, err); > > > + return err; > > > +} > > > + > > > +static int virtnet_tx_vq_reset(struct virtnet_info *vi, int i) > > > +{ > > > + int err; > > > + > > > + err = virtnet_tx_vq_disable(vi, vi->sq + i); > > > + if (err) > > > + return err; > > > + > > > + err = virtnet_tx_vq_enable(vi, vi->sq + i); > > > + if (err) > > > + netdev_err(vi->dev, > > > + "enable tx reset vq fail: tx queue index: %d err: %d\n", i, err); > > > + return err; > > > +} > > > + > > > /* > > > * Send command via the control virtqueue and check status. Commands > > > * supported by the hypervisor, as indicated by feature bits, should > > > -- > > > 2.31.0 > > > > >