vhost: don't bother with copying iovec in handle_tx()

just advance the msg.msg_iter and be done with that.

Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: kvm@vger.kernel.org
Cc: virtualization@lists.linux-foundation.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 5 insertions, 4 deletions

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 6906f76332f4..d86cc9bb9ea4 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -336,7 +336,7 @@ static void handle_tx(struct vhost_net *net)
 {
         struct vhost_net_virtqueue *nvq = &net->vqs[VHOST_NET_VQ_TX];
         struct vhost_virtqueue *vq = &nvq->vq;
-        unsigned out, in, s;
+        unsigned out, in;
         int head;
         struct msghdr msg = {
                 .msg_name = NULL,
@@ -395,16 +395,17 @@ static void handle_tx(struct vhost_net *net)
                         break;
                 }
                 /* Skip header. TODO: support TSO. */
-                s = move_iovec_hdr(vq->iov, nvq->hdr, hdr_size, out);
                 len = iov_length(vq->iov, out);
                 iov_iter_init(&msg.msg_iter, WRITE, vq->iov, out, len);
+                iov_iter_advance(&msg.msg_iter, hdr_size);
                 /* Sanity check */
-                if (!len) {
+                if (!iov_iter_count(&msg.msg_iter)) {
                         vq_err(vq, "Unexpected header len for TX: "
                                "%zd expected %zd\n",
-                               iov_length(nvq->hdr, s), hdr_size);
+                               len, hdr_size);
                         break;
                 }
+                len = iov_iter_count(&msg.msg_iter);
 
                 zcopy_used = zcopy && len >= VHOST_GOODCOPY_LEN
                                    && (nvq->upend_idx + 1) % UIO_MAXIOV !=