Re: [Xen-devel] [PATCH V2 net-next 2/5] xen-netback: Add support for multiple queues

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Feb 14, 2014 at 11:50:21AM +0000, Andrew J. Bennieston wrote:
[...]
>  
> +extern unsigned int xenvif_max_queues;
> +
>  #endif /* __XEN_NETBACK__COMMON_H__ */
> diff --git a/drivers/net/xen-netback/interface.c 
> b/drivers/net/xen-netback/interface.c
> index 4cde112..4dc092c 100644
> --- a/drivers/net/xen-netback/interface.c
> +++ b/drivers/net/xen-netback/interface.c
> @@ -373,7 +373,12 @@ struct xenvif *xenvif_alloc(struct device *parent, 
> domid_t domid,
>       char name[IFNAMSIZ] = {};
>  
>       snprintf(name, IFNAMSIZ - 1, "vif%u.%u", domid, handle);
> -     dev = alloc_netdev_mq(sizeof(struct xenvif), name, ether_setup, 1);
> +     /* Allocate a netdev with the max. supported number of queues.
> +      * When the guest selects the desired number, it will be updated
> +      * via netif_set_real_num_tx_queues().
> +      */
> +     dev = alloc_netdev_mq(sizeof(struct xenvif), name, ether_setup,
> +                                               xenvif_max_queues);

Indentation.

>       if (dev == NULL) {
>               pr_warn("Could not allocate netdev for %s\n", name);
>               return ERR_PTR(-ENOMEM);
> diff --git a/drivers/net/xen-netback/netback.c 
> b/drivers/net/xen-netback/netback.c
> index 46b2f5b..aeb5ffa 100644
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -54,6 +54,9 @@
[...]
> @@ -490,6 +497,23 @@ static void connect(struct backend_info *be)
>       unsigned long credit_bytes, credit_usec;
>       unsigned int queue_index;
>       struct xenvif_queue *queue;
> +     unsigned int requested_num_queues;
> +
> +     /* Check whether the frontend requested multiple queues
> +      * and read the number requested.
> +      */
> +     err = xenbus_scanf(XBT_NIL, dev->otherend,
> +                     "multi-queue-num-queues",
> +                     "%u", &requested_num_queues);
> +     if (err < 0) {
> +             requested_num_queues = 1; /* Fall back to single queue */
> +     } else if (requested_num_queues > xenvif_max_queues) {
> +             /* buggy or malicious guest */
> +             xenbus_dev_fatal(dev, err,
> +                                              "guest requested %u queues, 
> exceeding the maximum of %u.",
> +                                              requested_num_queues, 
> xenvif_max_queues);

Indentation.

> +             return;
> +     }
>  
[...]
> @@ -547,29 +575,52 @@ static int connect_rings(struct backend_info *be, 
> struct xenvif_queue *queue)
>       unsigned long tx_ring_ref, rx_ring_ref;
>       unsigned int tx_evtchn, rx_evtchn;
>       int err;
> +     char *xspath = NULL;
> +     size_t xspathsize;
> +     const size_t xenstore_path_ext_size = 11; /* sufficient for 
> "/queue-NNN" */
> +
> +     /* If the frontend requested 1 queue, or we have fallen back
> +      * to single queue due to lack of frontend support for multi-
> +      * queue, expect the remaining XenStore keys in the toplevel
> +      * directory. Otherwise, expect them in a subdirectory called
> +      * queue-N.
> +      */
> +     if (queue->vif->num_queues == 1)
> +             xspath = (char *)dev->otherend;

Coding style.

> +     else {

Wei.

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