Re: [Qemu-devel] [PATCH] vhost-user: save features if the char dev is closed

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

On Tue, Sep 17, 2019 at 09:19:01PM +0200, Adrian Moreno wrote:
> That way the state can be correctly restored when the device is opened
> again. This might happen if the backend is restarted.
> 
> Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1738768
> Reported-by: Pei Zhang <pezhang@redhat.com>
> Fixes: 6ab79a20af3a (do not call vhost_net_cleanup() on running net from char user event)
> Cc: ddstreet@canonical.com
> Cc: Michael S. Tsirkin <mst@redhat.com>
> 
> Signed-off-by: Adrian Moreno <amorenoz@redhat.com>
> ---
>  net/vhost-user.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/net/vhost-user.c b/net/vhost-user.c
> index 51921de443..acf20cb9e0 100644
> --- a/net/vhost-user.c
> +++ b/net/vhost-user.c
> @@ -235,6 +235,13 @@ static void chr_closed_bh(void *opaque)
>  
>      s = DO_UPCAST(NetVhostUserState, nc, ncs[0]);
>  
> +    if (s->vhost_net) {
> +        uint64_t features = vhost_net_get_acked_features(s->vhost_net);
> +        if (features) {
> +            s->acked_features = features;
> +         }

why does it make sense to check if (features)?
0x0 is a valid feature bitmap, isn't it?

> +    }
> +
>      qmp_set_link(name, false, &err);
>  
>      qemu_chr_fe_set_handlers(&s->chr, NULL, NULL, net_vhost_user_event,
> -- 
> 2.21.0