Re: [Qemu-devel] [PATCH 5/7] vhost_net: move vhost_net_set_vq_index ahead at vhost_net_init

[Jason Wang <jasowang@redhat.com>]

On 09/08/2015 03:38 PM, Yuanhan Liu wrote:
> So that we could use the `vq_index' as well in the vhost_net_init
> stage, which is required when adding vhost-user multiple-queue support,
> where we need the vq_index to indicate which queue pair we are gonna
> initiate.
>
> vhost-user has no multiple queue support yet, hence no queue_index set
> before. Here is a quick set to 0 at net_vhost_user_init() stage, and it
> will be set properly soon in the next patch.
>
> Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
> ---
>  hw/net/vhost_net.c | 16 +++++++---------
>  net/vhost-user.c   |  1 +
>  2 files changed, 8 insertions(+), 9 deletions(-)
>
> diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> index f9441e9..141b557 100644
> --- a/hw/net/vhost_net.c
> +++ b/hw/net/vhost_net.c
> @@ -138,6 +138,11 @@ static int vhost_net_get_fd(NetClientState *backend)
>      }
>  }
>  
> +static void vhost_net_set_vq_index(struct vhost_net *net, int vq_index)
> +{
> +    net->dev.vq_index = vq_index;
> +}
> +
>  struct vhost_net *vhost_net_init(VhostNetOptions *options)
>  {
>      int r;
> @@ -167,6 +172,8 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options)
>      }
>      net->nc = options->net_backend;
>  
> +    vhost_net_set_vq_index(net, net->nc->queue_index * 2);
> +

This breaks vhost kernel multiqueue since queue_index was not
initialized at this time. We do this in set_netdev() instead of setting
it in each kind of netdev.

>      net->dev.nvqs = 2;
>      net->dev.vqs = net->vqs;
>  
> @@ -196,11 +203,6 @@ fail:
>      return NULL;
>  }
>  
> -static void vhost_net_set_vq_index(struct vhost_net *net, int vq_index)
> -{
> -    net->dev.vq_index = vq_index;
> -}
> -
>  static int vhost_net_set_vnet_endian(VirtIODevice *dev, NetClientState *peer,
>                                       bool set)
>  {
> @@ -325,10 +327,6 @@ int vhost_net_start(VirtIODevice *dev, NetClientState *ncs,
>          goto err;
>      }
>  
> -    for (i = 0; i < total_queues; i++) {
> -        vhost_net_set_vq_index(get_vhost_net(ncs[i].peer), i * 2);
> -    }
> -
>      r = k->set_guest_notifiers(qbus->parent, total_queues * 2, true);
>      if (r < 0) {
>          error_report("Error binding guest notifier: %d", -r);
> diff --git a/net/vhost-user.c b/net/vhost-user.c
> index 93dcecd..2d6bbe5 100644
> --- a/net/vhost-user.c
> +++ b/net/vhost-user.c
> @@ -146,6 +146,7 @@ static int net_vhost_user_init(NetClientState *peer, const char *device,
>      /* We don't provide a receive callback */
>      s->nc.receive_disabled = 1;
>      s->chr = chr;
> +    nc->queue_index = 0;
>  

Fail to understand why this is needed. It will be set to correct value
in set_netdev().

>      qemu_chr_add_handlers(s->chr, NULL, NULL, net_vhost_user_event, s);
>