The current implementation may change the packet layout when
vnet_hdr needs an endianness swap. The layout change causes
one more iov to be added to the iov[] passed from the guest, which
is a barrier to making the TX queue size 1024 due to the possible
off-by-one issue.
This patch changes the implementation to remain the packet layout
intact. In this case, the number of iov[] passed to writev will be
equal to the number obtained from the guest.
Signed-off-by: Wei Wang <wei.w.w...@intel.com>
---
hw/net/virtio-net.c | 29 ++++++++++++++---------------
1 file changed, 14 insertions(+), 15 deletions(-)
diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 7d091c9..a51e9a8 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -1287,8 +1287,7 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q)
for (;;) {
ssize_t ret;
unsigned int out_num;
- struct iovec sg[VIRTQUEUE_MAX_SIZE], sg2[VIRTQUEUE_MAX_SIZE + 1],
*out_sg;
- struct virtio_net_hdr_mrg_rxbuf mhdr;
+ struct iovec sg[VIRTQUEUE_MAX_SIZE], mhdr, *out_sg;
elem = virtqueue_pop(q->tx_vq, sizeof(VirtQueueElement));
if (!elem) {
@@ -1305,7 +1304,10 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q)
}
if (n->has_vnet_hdr) {
- if (iov_to_buf(out_sg, out_num, 0, &mhdr, n->guest_hdr_len) <
+ /* Buffer to copy vnet_hdr and the possible adjacent data */
+ mhdr.iov_len = out_sg[0].iov_len;
+ mhdr.iov_base = g_malloc0(mhdr.iov_len);
+ if (iov_to_buf(out_sg, out_num, 0, mhdr.iov_base, mhdr.iov_len) <
n->guest_hdr_len) {
virtio_error(vdev, "virtio-net header incorrect");
virtqueue_detach_element(q->tx_vq, elem, 0);
@@ -1313,17 +1315,12 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q)
return -EINVAL;
}
if (n->needs_vnet_hdr_swap) {
- virtio_net_hdr_swap(vdev, (void *) &mhdr);
- sg2[0].iov_base = &mhdr;
- sg2[0].iov_len = n->guest_hdr_len;
- out_num = iov_copy(&sg2[1], ARRAY_SIZE(sg2) - 1,
- out_sg, out_num,
- n->guest_hdr_len, -1);
- if (out_num == VIRTQUEUE_MAX_SIZE) {
- goto drop;
- }
- out_num += 1;
- out_sg = sg2;
+ virtio_net_hdr_swap(vdev, mhdr.iov_base);
+ /* Copy the first iov where the vnet_hdr resides in */
+ out_num = iov_copy(sg, 1, &mhdr, 1, 0, mhdr.iov_len);
+ out_num += iov_copy(sg + 1, ARRAY_SIZE(sg) - 1, out_sg + 1,
+ elem->out_num - 1, 0, -1);
+ out_sg = sg;
}
}
/*
@@ -1345,13 +1342,15 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q)
ret = qemu_sendv_packet_async(qemu_get_subqueue(n->nic, queue_index),
out_sg, out_num,
virtio_net_tx_complete);
+ if (n->has_vnet_hdr) {
+ g_free(mhdr.iov_base);
+ }
if (ret == 0) {
virtio_queue_set_notification(q->tx_vq, 0);
q->async_tx.elem = elem;
return -EBUSY;
}
-drop:
virtqueue_push(q->tx_vq, elem, 0);
virtio_notify(vdev, q->tx_vq);
g_free(elem);
