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

From: Andrew Bennieston <[email-masked]>
Date: Fri, 14 Feb 2014 14:57:25 +0000

On 14/02/14 14:11, Wei Liu wrote:
> 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.

How would you like this to be indented? The CodingStyle says (and I quote):
Chapter 2: Breaking long lines and strings:
	... descendants are always substantially shorter than the
	parent and placed substantially to the right...

There is no further advice to this point in CodingStyle, so please 
explain how you'd prefer this.

>
>>   	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.
Ditto.

>
>> +		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.
>
Ok; I thought I'd caught all of those. I'll change it.

>> +	else {
> Wei.