From: Tonghao Zhang <redacted>

Factor out generic busy polling logic and will be
used for tx path in the next patch. And with the patch,
qemu can set differently the busyloop_timeout for rx queue.

Signed-off-by: Tonghao Zhang <redacted>
---
  drivers/vhost/net.c | 92 ++++++++++++++++++++++++++++++-----------------------
  1 file changed, 53 insertions(+), 39 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 62bb8e8..458f81d 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c

@@ -429,6 +429,50 @@ static int vhost_net_enable_vq(struct vhost_net *n,
  	return vhost_poll_start(poll, sock->file);
  }
  
+static int sk_has_rx_data(struct sock *sk)
+{
+	struct socket *sock = sk->sk_socket;
+
+	if (sock->ops->peek_len)
+		return sock->ops->peek_len(sock);
+
+	return skb_queue_empty(&sk->sk_receive_queue);
+}
+
+static void vhost_net_busy_poll(struct vhost_net *net,
+				struct vhost_virtqueue *rvq,
+				struct vhost_virtqueue *tvq,
+				bool rx)
+{
+	unsigned long uninitialized_var(endtime);
+	struct socket *sock = rvq->private_data;
+	struct vhost_virtqueue *vq = rx ? tvq : rvq;
+	unsigned long busyloop_timeout = rx ? rvq->busyloop_timeout :
+					      tvq->busyloop_timeout;

+	vhost_disable_notify(&net->dev, vq);
+
+	preempt_disable();
+	endtime = busy_clock() + busyloop_timeout;
+	while (vhost_can_busy_poll(tvq->dev, endtime) &&
+	       !(sock && sk_has_rx_data(sock->sk)) &&
+	       vhost_vq_avail_empty(tvq->dev, tvq))
+		cpu_relax();
+	preempt_enable();
+
+	if ((rx && !vhost_vq_avail_empty(&net->dev, vq)) ||
+	    (!rx && (sock && sk_has_rx_data(sock->sk)))) {
+		vhost_poll_queue(&vq->poll);
+	} else if (unlikely(vhost_enable_notify(&net->dev, vq))) {
+		vhost_disable_notify(&net->dev, vq);
+		vhost_poll_queue(&vq->poll);
+	}
+
+	mutex_unlock(&vq->mutex);
+}
+
+
  static int vhost_net_tx_get_vq_desc(struct vhost_net *net,
  				    struct vhost_virtqueue *vq,
  				    struct iovec iov[], unsigned int iov_size,

@@ -621,16 +665,6 @@ static int peek_head_len(struct vhost_net_virtqueue *rvq, struct sock *sk)
  	return len;
  }
  
-static int sk_has_rx_data(struct sock *sk)
-{
-	struct socket *sock = sk->sk_socket;
-
-	if (sock->ops->peek_len)
-		return sock->ops->peek_len(sock);
-
-	return skb_queue_empty(&sk->sk_receive_queue);
-}
-
  static void vhost_rx_signal_used(struct vhost_net_virtqueue *nvq)
  {
  	struct vhost_virtqueue *vq = &nvq->vq;

@@ -645,39 +679,19 @@ static void vhost_rx_signal_used(struct vhost_net_virtqueue *nvq)
  
  static int vhost_net_rx_peek_head_len(struct vhost_net *net, struct sock *sk)
  {
-	struct vhost_net_virtqueue *rvq = &net->vqs[VHOST_NET_VQ_RX];
-	struct vhost_net_virtqueue *nvq = &net->vqs[VHOST_NET_VQ_TX];
-	struct vhost_virtqueue *vq = &nvq->vq;
-	unsigned long uninitialized_var(endtime);
-	int len = peek_head_len(rvq, sk);
+	struct vhost_net_virtqueue *nvq_rx = &net->vqs[VHOST_NET_VQ_RX];
+	struct vhost_net_virtqueue *nvq_tx = &net->vqs[VHOST_NET_VQ_TX];