vhost-net: unbreak busy polling

Commit 67a873df0c41 ("vhost: basic in order support") pass the number
of used elem to vhost_net_rx_peek_head_len() to make sure it can
signal the used correctly before trying to do busy polling. But it
forgets to clear the count, this would cause the count run out of sync
with handle_rx() and break the busy polling.

Fixing this by passing the pointer of the count and clearing it after
the signaling the used.

Acked-by: Michael S. Tsirkin <mst@redhat.com>
Cc: stable@vger.kernel.org
Fixes: 67a873df0c41 ("vhost: basic in order support")
Signed-off-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20250917063045.2042-1-jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index c6508fe0d5c8e5e55def90f715922cc6f5df4c9e..16e39f3ab9566f9539214f678402b09f6b6a9bf6 100644 (file)
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -1014,7 +1014,7 @@ static int peek_head_len(struct vhost_net_virtqueue *rvq, struct sock *sk)
 }
 
 static int vhost_net_rx_peek_head_len(struct vhost_net *net, struct sock *sk,
-                                     bool *busyloop_intr, unsigned int count)
+                                     bool *busyloop_intr, unsigned int *count)
 {
        struct vhost_net_virtqueue *rnvq = &net->vqs[VHOST_NET_VQ_RX];
        struct vhost_net_virtqueue *tnvq = &net->vqs[VHOST_NET_VQ_TX];
@@ -1024,7 +1024,8 @@ static int vhost_net_rx_peek_head_len(struct vhost_net *net, struct sock *sk,
 
        if (!len && rvq->busyloop_timeout) {
                /* Flush batched heads first */
-               vhost_net_signal_used(rnvq, count);
+               vhost_net_signal_used(rnvq, *count);
+               *count = 0;
                /* Both tx vq and rx socket were polled here */
                vhost_net_busy_poll(net, rvq, tvq, busyloop_intr, true);
 
@@ -1180,7 +1181,7 @@ static void handle_rx(struct vhost_net *net)
 
        do {
                sock_len = vhost_net_rx_peek_head_len(net, sock->sk,
-                                                     &busyloop_intr, count);
+                                                     &busyloop_intr, &count);
                if (!sock_len)
                        break;
                sock_len += sock_hlen;