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Date: Wed, 16 Feb 2022 12:14:11 +0800
From: Jason Wang <jasowang@...hat.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc: virtualization <virtualization@...ts.linux-foundation.org>,
netdev <netdev@...r.kernel.org>,
"Michael S. Tsirkin" <mst@...hat.com>,
"David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Jesper Dangaard Brouer <hawk@...nel.org>,
John Fastabend <john.fastabend@...il.com>, bpf@...r.kernel.org
Subject: Re: [PATCH v5 17/22] virtio_net: support rx/tx queue reset
On Mon, Feb 14, 2022 at 4:14 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> 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 <xuanzhuo@...ux.alibaba.com>
> ---
> 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
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
>
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