Re: [Xen-devel] [PATCH v3 12/18] xen/pvcalls: implement poll command

[Juergen Gross <jgross@xxxxxxxx>]

On 02/06/17 21:31, Stefano Stabellini wrote:
> Implement poll on passive sockets by requesting a delayed response with
> mappass->reqcopy, and reply back when there is data on the passive
> socket.
> 
> Poll on active socket is unimplemented as by the spec, as the frontend
> should just wait for events and check the indexes on the indexes page.
> 
> Only support one outstanding poll (or accept) request for every passive
> socket at any given time.
> 
> Signed-off-by: Stefano Stabellini <stefano@xxxxxxxxxxx>
> CC: boris.ostrovsky@xxxxxxxxxx
> CC: jgross@xxxxxxxx
> ---
>  drivers/xen/pvcalls-back.c | 75 
> ++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 73 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/xen/pvcalls-back.c b/drivers/xen/pvcalls-back.c
> index f1173f4..82f350d 100644
> --- a/drivers/xen/pvcalls-back.c
> +++ b/drivers/xen/pvcalls-back.c
> @@ -344,11 +344,33 @@ static void __pvcalls_back_accept(struct work_struct 
> *work)
>  static void pvcalls_pass_sk_data_ready(struct sock *sock)
>  {
>       struct sockpass_mapping *mappass = sock->sk_user_data;
> +     struct pvcalls_fedata *priv;
> +     struct xen_pvcalls_response *rsp;
> +     unsigned long flags;
> +     int notify;
>  
>       if (mappass == NULL)
>               return;
>  
> -     queue_work(mappass->wq, &mappass->register_work);
> +     priv = mappass->priv;
> +     spin_lock_irqsave(&mappass->copy_lock, flags);
> +     if (mappass->reqcopy.cmd == PVCALLS_POLL) {
> +             rsp = RING_GET_RESPONSE(&priv->ring, priv->ring.rsp_prod_pvt++);
> +             rsp->req_id = mappass->reqcopy.req_id;
> +             rsp->u.poll.id = mappass->reqcopy.u.poll.id;
> +             rsp->cmd = mappass->reqcopy.cmd;
> +             rsp->ret = 0;
> +
> +             mappass->reqcopy.cmd = 0;
> +             spin_unlock_irqrestore(&mappass->copy_lock, flags);
> +
> +             RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&priv->ring, notify);
> +             if (notify)
> +                     notify_remote_via_irq(mappass->priv->irq);
> +     } else {
> +             spin_unlock_irqrestore(&mappass->copy_lock, flags);
> +             queue_work(mappass->wq, &mappass->register_work);
> +     }
>  }
>  
>  static int pvcalls_back_bind(struct xenbus_device *dev,
> @@ -493,7 +515,56 @@ static int pvcalls_back_accept(struct xenbus_device *dev,
>  static int pvcalls_back_poll(struct xenbus_device *dev,
>                            struct xen_pvcalls_request *req)
>  {
> -     return 0;
> +     struct pvcalls_fedata *priv;
> +     struct sockpass_mapping *mappass;
> +     struct xen_pvcalls_response *rsp;
> +     struct inet_connection_sock *icsk;
> +     struct request_sock_queue *queue;
> +     unsigned long flags;
> +     int ret;
> +     bool data;
> +
> +     priv = dev_get_drvdata(&dev->dev);
> +
> +     mappass = radix_tree_lookup(&priv->socketpass_mappings, req->u.poll.id);
> +     if (mappass == NULL)
> +             return -EINVAL;
> +
> +     /*
> +      * Limitation of the current implementation: only support one
> +      * concurrent accept or poll call on one socket.
> +      */
> +     spin_lock_irqsave(&mappass->copy_lock, flags);
> +     if (mappass->reqcopy.cmd != 0) {
> +             ret = -EINTR;
> +             goto out;
> +     }
> +
> +     mappass->reqcopy = *req;
> +     icsk = inet_csk(mappass->sock->sk);
> +     queue = &icsk->icsk_accept_queue;
> +     spin_lock(&queue->rskq_lock);
> +     data = queue->rskq_accept_head != NULL;
> +     spin_unlock(&queue->rskq_lock);
> +     if (data) {
> +             mappass->reqcopy.cmd = 0;
> +             ret = 0;
> +             goto out;
> +     }
> +     spin_unlock_irqrestore(&mappass->copy_lock, flags);
> +
> +     /* Tell the caller we don't need to send back a notification yet */
> +     return -1;
> +
> +out:
> +     spin_unlock_irqrestore(&mappass->copy_lock, flags);
> +
> +     rsp = RING_GET_RESPONSE(&priv->ring, priv->ring.rsp_prod_pvt++);
> +     rsp->req_id = req->req_id;
> +     rsp->cmd = req->cmd;
> +     rsp->u.poll.id = req->u.poll.id;
> +     rsp->ret = ret;
> +     return ret;

return 0;


Juergen

>  }
>  
>  static int pvcalls_back_handle_cmd(struct xenbus_device *dev,
> 


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