On Mon, Oct 15, 2018 at 03:45:46PM +0800, Jason Wang wrote:
>
>
> On 2018年10月11日 22:08, w...@redhat.com wrote:
> >From: Wei Xu <w...@redhat.com>
> >
> >With the support of marking a descriptor used/unused in 'flags'
> >field for 1.1, the current way of filling a chained descriptors
> >does not work since driver side may get the wrong 'num_buffer'
> >information in case of the head descriptor has been filled in
> >while the subsequent ones are still in processing in device side.
> >
> >This patch fills the head one after done all the others one.
> >
> >Signed-off-by: Wei Xu <w...@redhat.com>
> >---
> > hw/net/virtio-net.c | 11 ++++++++++-
> > 1 file changed, 10 insertions(+), 1 deletion(-)
> >
> >diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> >index 4bdd5b8..186c86cd2 100644
> >--- a/hw/net/virtio-net.c
> >+++ b/hw/net/virtio-net.c
> >@@ -1198,6 +1198,8 @@ static ssize_t virtio_net_receive_rcu(NetClientState
> >*nc, const uint8_t *buf,
> > struct virtio_net_hdr_mrg_rxbuf mhdr;
> > unsigned mhdr_cnt = 0;
> > size_t offset, i, guest_offset;
> >+ VirtQueueElement head;
> >+ int head_len = 0;
> > if (!virtio_net_can_receive(nc)) {
> > return -1;
> >@@ -1275,7 +1277,13 @@ static ssize_t virtio_net_receive_rcu(NetClientState
> >*nc, const uint8_t *buf,
> > }
> > /* signal other side */
> >- virtqueue_fill(q->rx_vq, elem, total, i++);
> >+ if (i == 0) {
> >+ head_len = total;
> >+ head = *elem;
> >+ } else {
> >+ virtqueue_fill(q->rx_vq, elem, len, i);
> >+ }
> >+ i++;
> > g_free(elem);
> > }
> >@@ -1286,6 +1294,7 @@ static ssize_t virtio_net_receive_rcu(NetClientState
> >*nc, const uint8_t *buf,
> > &mhdr.num_buffers, sizeof mhdr.num_buffers);
> > }
> >+ virtqueue_fill(q->rx_vq, &head, head_len, 0);
>
> It's not a good idea to fix API in device implementation. Let's introduce
> new API and fix it there.
>
> E.g virtqueue_fill_n() and update the flag of first elem at the last step.
OK, I haven't considered about the other devices so far.
Wei
>
> Thanks
>
> > virtqueue_flush(q->rx_vq, i);
> > virtio_notify(vdev, q->rx_vq);
>
>
