Re: [PATCH v2 1/2] vhost-user: Refactor vhost acked features saving

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

On Sat, Oct 29, 2022 at 01:25:44AM +0800, huangy81@chinatelecom.cn wrote:
> From: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>
> 
> Abstract vhost acked features saving into
> vhost_user_save_acked_features, export it as util function.
>

Thanks for the patch!

This commit log makes it sound like it's just a refactoring
while it's actually a behaviour change.
This log needs to include analysis of why is saving only if features != 0
safe.

Could you include that pls?

Thanks!
 
> Signed-off-by: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>
> Signed-off-by: Guoyi Tu <tugy@chinatelecom.cn>
> ---
>  include/net/vhost-user.h |  2 ++
>  net/vhost-user.c         | 35 +++++++++++++++++++----------------
>  2 files changed, 21 insertions(+), 16 deletions(-)
> 
> diff --git a/include/net/vhost-user.h b/include/net/vhost-user.h
> index 5bcd8a6..00d4661 100644
> --- a/include/net/vhost-user.h
> +++ b/include/net/vhost-user.h
> @@ -14,5 +14,7 @@
>  struct vhost_net;
>  struct vhost_net *vhost_user_get_vhost_net(NetClientState *nc);
>  uint64_t vhost_user_get_acked_features(NetClientState *nc);
> +void vhost_user_save_acked_features(NetClientState *nc,
> +                                    bool cleanup);
>  
>  #endif /* VHOST_USER_H */
> diff --git a/net/vhost-user.c b/net/vhost-user.c
> index b1a0247..c512cc9 100644
> --- a/net/vhost-user.c
> +++ b/net/vhost-user.c
> @@ -45,24 +45,31 @@ uint64_t vhost_user_get_acked_features(NetClientState *nc)
>      return s->acked_features;
>  }
>  
> -static void vhost_user_stop(int queues, NetClientState *ncs[])
> +void vhost_user_save_acked_features(NetClientState *nc, bool cleanup)
>  {
>      NetVhostUserState *s;
> +
> +    s = DO_UPCAST(NetVhostUserState, nc, nc);
> +    if (s->vhost_net) {
> +        uint64_t features = vhost_net_get_acked_features(s->vhost_net);
> +        if (features) {
> +            s->acked_features = features;
> +        }
> +
> +        if (cleanup) {
> +            vhost_net_cleanup(s->vhost_net);
> +        }
> +    }
> +}
> +
> +static void vhost_user_stop(int queues, NetClientState *ncs[])
> +{
>      int i;
>  
>      for (i = 0; i < queues; i++) {
>          assert(ncs[i]->info->type == NET_CLIENT_DRIVER_VHOST_USER);
>  
> -        s = DO_UPCAST(NetVhostUserState, nc, ncs[i]);
> -
> -        if (s->vhost_net) {
> -            /* save acked features */
> -            uint64_t features = vhost_net_get_acked_features(s->vhost_net);
> -            if (features) {
> -                s->acked_features = features;
> -            }
> -            vhost_net_cleanup(s->vhost_net);
> -        }
> +        vhost_user_save_acked_features(ncs[i], true);
>      }
>  }
>  
> @@ -251,11 +258,7 @@ static void chr_closed_bh(void *opaque)
>      s = DO_UPCAST(NetVhostUserState, nc, ncs[0]);
>  
>      for (i = queues -1; i >= 0; i--) {
> -        s = DO_UPCAST(NetVhostUserState, nc, ncs[i]);
> -
> -        if (s->vhost_net) {
> -            s->acked_features = vhost_net_get_acked_features(s->vhost_net);
> -        }
> +        vhost_user_save_acked_features(ncs[i], false);


So this won't do anything if acked features is 0.
When does this have any effect? How about if guest
acked some features, and then reset the device.
Don't we want to reset the features in this case too?


>      }
>  
>      qmp_set_link(name, false, &err);
> -- 
> 1.8.3.1