vhost: fix dequeue offload support

When offload is enabled, vhost needs to access the first mbuf
to get the packet info, e.g. TCP header. So we couldn't delay
the data copy in this case.

Fixes: e5c494a7a22b ("vhost: batch small guest memory copies")

Reported-by: Lei Yao <lei.a.yao@intel.com>
Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Acked-by: Yuanhan Liu <yliu@fridaylinux.org>

diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index b75c93c..3c6f1a5 100644 (file)
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -987,7 +987,8 @@ copy_desc_to_mbuf(struct virtio_net *dev, struct vhost_virtqueue *vq,
                        mbuf_avail = cpy_len;
                } else {
                        if (likely(cpy_len > MAX_BATCH_LEN ||
-                                  copy_nb >= vq->size)) {
+                                  copy_nb >= vq->size ||
+                                  (hdr && cur == m))) {
                                rte_memcpy(rte_pktmbuf_mtod_offset(cur, void *,
                                                                   mbuf_offset),
                                           (void *)((uintptr_t)(desc_addr +