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From: Jason Wang <jasowang@redhat.com>
To: wexu@redhat.com, qemu-devel@nongnu.org
Cc: tiwei.bie@intel.com, jfreimann@redhat.com, maxime.coquelin@redhat.com
Subject: Re: [Qemu-devel] [[RFC v3 09/12] virtio-net: fill head desc after done all in a chain
Date: Mon, 15 Oct 2018 15:45:46 +0800	[thread overview]
Message-ID: <fb04c68b-024b-5be8-00ea-e558f9ae0d12@redhat.com> (raw)
In-Reply-To: <1539266915-15216-10-git-send-email-wexu@redhat.com>



On 2018年10月11日 22:08, wexu@redhat.com wrote:
> From: Wei Xu <wexu@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 <wexu@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.

Thanks

>       virtqueue_flush(q->rx_vq, i);
>       virtio_notify(vdev, q->rx_vq);
>   

  reply	other threads:[~2018-10-15  7:46 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-11 14:08 [Qemu-devel] [RFC v3 00/12] packed ring virtio-net userspace backend support wexu
2018-10-11 14:08 ` [Qemu-devel] [[RFC v3 01/12] virtio: introduce packed ring definitions wexu
2018-10-11 14:08 ` [Qemu-devel] [[RFC v3 02/12] virtio: redefine structure & memory cache for packed ring wexu
2018-10-15  3:03   ` Jason Wang
2018-10-15  7:26     ` Wei Xu
2018-10-15  8:03       ` Jason Wang
2018-10-11 14:08 ` [Qemu-devel] [[RFC v3 03/12] virtio: init " wexu
2018-10-15  3:10   ` Jason Wang
2018-10-15  7:09     ` Wei Xu
2018-10-15  7:54       ` Jason Wang
2018-10-11 14:08 ` [Qemu-devel] [[RFC v3 04/12] virtio: init wrap counter " wexu
2018-10-11 14:08 ` [Qemu-devel] [[RFC v3 05/12] virtio: init and desc empty check " wexu
2018-10-15  3:18   ` Jason Wang
2018-10-15  7:04     ` Wei Xu
2018-10-11 14:08 ` [Qemu-devel] [[RFC v3 06/12] virtio: get avail bytes " wexu
2018-10-15  3:47   ` Jason Wang
2018-10-11 14:08 ` [Qemu-devel] [[RFC v3 07/12] virtio: fill/flush/pop " wexu
2018-10-15  6:14   ` Jason Wang
2018-10-11 14:08 ` [Qemu-devel] [[RFC v3 08/12] virtio: event suppression support " wexu
2018-10-15  6:55   ` Jason Wang
2018-10-15  6:59   ` Jason Wang
2018-10-15  8:20     ` Wei Xu
2018-10-15  9:11       ` Jason Wang
2018-10-11 14:08 ` [Qemu-devel] [[RFC v3 09/12] virtio-net: fill head desc after done all in a chain wexu
2018-10-15  7:45   ` Jason Wang [this message]
2018-10-15  8:03     ` Wei Xu
2018-10-15  8:05       ` Jason Wang
2018-10-11 14:08 ` [Qemu-devel] [[RFC v3 10/12] virtio: packed ring feature bit for userspace backend wexu
2018-10-11 14:08 ` [Qemu-devel] [[RFC v3 11/12] virtio: enable packed ring via a new command line wexu
2018-10-11 14:08 ` [Qemu-devel] [[RFC v3 12/12] virtio: feature vhost-net support for packed ring wexu
2018-10-15  7:50   ` Jason Wang
2018-10-15  8:11     ` Wei Xu
2018-11-21 13:03   ` Maxime Coquelin
2018-11-22  3:46     ` Wei Xu
2018-11-21 14:39 ` [Qemu-devel] [RFC v3 00/12] packed ring virtio-net userspace backend support Tiwei Bie
2018-11-22  3:43   ` Wei Xu

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