[PATCH v11 39/40] virtio_net: support tx queue resize

Xuan Zhuo
2022-06-29T07:01:58Z

This patch implements the resize function of the tx queues.
Based on this function, it is possible to modify the ring num of the
queue.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
---
drivers/net/virtio_net.c | 48 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 48 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 6ab16fd193e5..fd358462f802 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -135,6 +135,9 @@ struct send_queue {
struct virtnet_sq_stats stats;

struct napi_struct napi;
+
+ /* Record whether sq is in reset state. */
+ bool reset;
};

/* Internal representation of a receive virtqueue */
@@ -279,6 +282,7 @@ struct padded_vnet_hdr {
};

static void virtnet_rq_free_unused_buf(struct virtqueue *vq, void *buf);
+static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void *buf);

static bool is_xdp_frame(void *ptr)
{
@@ -1603,6 +1607,11 @@ static void virtnet_poll_cleantx(struct receive_queue *rq)
return;

if (__netif_tx_trylock(txq)) {
+ if (READ_ONCE(sq->reset)) {
+ __netif_tx_unlock(txq);
+ return;
+ }
+
do {
virtqueue_disable_cb(sq->vq);
free_old_xmit_skbs(sq, true);
@@ -1868,6 +1877,45 @@ static int virtnet_rx_resize(struct virtnet_info *vi,
return err;
}

+static int virtnet_tx_resize(struct virtnet_info *vi,
+ struct send_queue *sq, u32 ring_num)
+{
+ struct netdev_queue *txq;
+ int err, qindex;
+
+ qindex = sq - vi->sq;
+
+ virtnet_napi_tx_disable(&sq->napi);
+
+ txq = netdev_get_tx_queue(vi->dev, qindex);
+
+ /* 1. wait all ximt complete
+ * 2. fix the race of netif_stop_subqueue() vs netif_start_subqueue()
+ */
+ __netif_tx_lock_bh(txq);
+
+ /* Prevent rx poll from accessing sq. */
+ WRITE_ONCE(sq->reset, true);
+
+ /* Prevent the upper layer from trying to send packets. */
+ netif_stop_subqueue(vi->dev, qindex);
+
+ __netif_tx_unlock_bh(txq);
+
+ err = virtqueue_resize(sq->vq, ring_num, virtnet_sq_free_unused_buf);
+ if (err)
+ netdev_err(vi->dev, "resize tx fail: tx queue index: %d err: %d\n", qindex, err);
+
+ /* Memory barrier before set reset and start subqueue. */
+ smp_mb();
+
+ WRITE_ONCE(sq->reset, false);
+ netif_tx_wake_queue(txq);
+
+ virtnet_napi_tx_enable(vi, sq->vq, &sq->napi);
+ 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