[Qemu-devel] Re: [PATCH] vhost-net: Do not set features for backend when peer was deleted

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Oct 27, 2010 at 12:43:51AM +0800, Jason Wang wrote:
> When hot-unplug a virtio nic with vhost-net backend, guest may
> continue to program the nic even if its peer have been deleted. We can
> not set features at this time as vhost_net_ack_features() may still
> try to use the tap related vhost_net structure which have been freed
> in tap_cleanup(). And setting offload features for a deleted backend
> is also meaningless in this situation
> 
> Signed-off-by: Jason Wang <jasowang@redhat.com>

Hmm. Actually, this is not enough.
We really must stop and cleanup vhost net.

Two issues are 
1. vhost_net_stop needs virtio device pointer
2. virtio net has a vhost_started flag

Two ways to fix it that I see:
1. add a callback in nic and invoke when peer_deleted is set
2. add vhost_started and virtio device pointers in vhost

Path 1 seems easier ...

MST

> ---
>  hw/virtio-net.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
> 
> diff --git a/hw/virtio-net.c b/hw/virtio-net.c
> index 7e1688c..68c8e48 100644
> --- a/hw/virtio-net.c
> +++ b/hw/virtio-net.c
> @@ -245,6 +245,9 @@ static void virtio_net_set_features(VirtIODevice *vdev, uint32_t features)
>  {
>      VirtIONet *n = to_virtio_net(vdev);
>  
> +    if (n->nic->peer_deleted)
> +        return;
> +
>      n->mergeable_rx_bufs = !!(features & (1 << VIRTIO_NET_F_MRG_RXBUF));
>  
>      if (n->has_vnet_hdr) {