Subject: Re: [Xen-devel] [RFC PATCH V3 16/16] netfront: split event channels support.

From: Konrad Rzeszutek Wilk <[email-masked]>
Date: Mon, 30 Jan 2012 16:25:15 -0500

On Mon, Jan 30, 2012 at 02:45:34PM +0000, Wei Liu wrote:
> If this feature is not activated, rx_irq = tx_irq. See corresponding
> netback change log for details.
> 
> Signed-off-by: Wei Liu <[email-masked]>
> ---
>  drivers/net/xen-netfront.c |  147 ++++++++++++++++++++++++++++++++++----------
>  1 files changed, 115 insertions(+), 32 deletions(-)
> 
> diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
> index 32ec212..72c0429 100644
> --- a/drivers/net/xen-netfront.c
> +++ b/drivers/net/xen-netfront.c
> @@ -98,7 +98,9 @@ struct netfront_info {
>  
>  	unsigned long rx_gso_checksum_fixup;
>  
> -	unsigned int evtchn;
> +	unsigned int split_evtchn;

bool?

> +	unsigned int tx_evtchn, rx_evtchn;
> +	unsigned int tx_irq, rx_irq;
>  	struct xenbus_device *xbdev;
>  
>  	spinlock_t   tx_lock;
> @@ -344,7 +346,7 @@ no_skb:
>   push:
>  	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&np->rx, notify);
>  	if (notify)
> -		notify_remote_via_irq(np->netdev->irq);
> +		notify_remote_via_irq(np->rx_irq);
>  }
>  
>  static int xennet_open(struct net_device *dev)
> @@ -577,7 +579,7 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
>  
>  	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&np->tx, notify);
>  	if (notify)
> -		notify_remote_via_irq(np->netdev->irq);
> +		notify_remote_via_irq(np->tx_irq);
>  
>  	u64_stats_update_begin(&stats->syncp);
>  	stats->tx_bytes += skb->len;
> @@ -1242,22 +1244,35 @@ static int xennet_set_features(struct net_device *dev, u32 features)
>  	return 0;
>  }
>  
> -static irqreturn_t xennet_interrupt(int irq, void *dev_id)
> +static irqreturn_t xennet_tx_interrupt(int irq, void *dev_id)
>  {
> -	struct net_device *dev = dev_id;
> -	struct netfront_info *np = netdev_priv(dev);
> +	struct netfront_info *np = dev_id;
> +	struct net_device *dev = np->netdev;
>  	unsigned long flags;
>  
>  	spin_lock_irqsave(&np->tx_lock, flags);
> +	xennet_tx_buf_gc(dev);
> +	spin_unlock_irqrestore(&np->tx_lock, flags);
>  
> -	if (likely(netif_carrier_ok(dev))) {
> -		xennet_tx_buf_gc(dev);
> -		/* Under tx_lock: protects access to rx shared-ring indexes. */
> -		if (RING_HAS_UNCONSUMED_RESPONSES(&np->rx))
> -			napi_schedule(&np->napi);
> -	}
> +	return IRQ_HANDLED;
> +}
>  
> -	spin_unlock_irqrestore(&np->tx_lock, flags);
> +static irqreturn_t xennet_rx_interrupt(int irq, void *dev_id)
> +{
> +	struct netfront_info *np = dev_id;
> +	struct net_device *dev = np->netdev;
> +
> +	if (likely(netif_carrier_ok(dev)) &&
> +	    RING_HAS_UNCONSUMED_RESPONSES(&np->rx))
> +		napi_schedule(&np->napi);
> +
> +	return IRQ_HANDLED;
> +}
> +static irqreturn_t xennet_interrupt(int irq, void *dev_id)
> +{
> +	xennet_tx_interrupt(0, dev_id);
> +
> +	xennet_rx_interrupt(0, dev_id);
>  
>  	return IRQ_HANDLED;
>  }
> @@ -1436,9 +1451,14 @@ static void xennet_disconnect_backend(struct netfront_info *info)
>  	spin_unlock_irq(&info->tx_lock);
>  	spin_unlock_bh(&info->rx_lock);
>  
> -	if (info->netdev->irq)
> -		unbind_from_irqhandler(info->netdev->irq, info->netdev);
> -	info->evtchn = info->netdev->irq = 0;
> +	if (info->tx_irq && (info->tx_irq == info->rx_irq))
> +		unbind_from_irqhandler(info->tx_irq, info);
> +	if (info->tx_irq && (info->tx_irq != info->rx_irq)) {
> +		unbind_from_irqhandler(info->tx_irq, info);
> +		unbind_from_irqhandler(info->rx_irq, info);
> +	}
> +	info->tx_evtchn = info->tx_irq = 0;
> +	info->rx_evtchn = info->rx_irq = 0;
>  
>  	for (i = 0; i < info->tx_ring_pages; i++) {
>  		int ref = info->tx_ring_ref[i];
> @@ -1507,6 +1527,7 @@ static int setup_netfront(struct xenbus_device *dev, struct netfront_info *info)
>  	int err;
>  	struct net_device *netdev = info->netdev;
>  	unsigned int max_tx_ring_page_order, max_rx_ring_page_order;
> +	unsigned int split_evtchn;
>  	int i, j;
>  
>  	for (i = 0; i < XENNET_MAX_RING_PAGES; i++) {
> @@ -1515,7 +1536,6 @@ static int setup_netfront(struct xenbus_device *dev, struct netfront_info *info)
>  	}
>  	info->rx.sring = NULL;
>  	info->tx.sring = NULL;
> -	netdev->irq = 0;
>  
>  	err = xen_net_read_mac(dev, netdev->dev_addr);
>  	if (err) {
> @@ -1524,6 +1544,12 @@ static int setup_netfront(struct xenbus_device *dev, struct netfront_info *info)
>  	}
>  
>  	err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
> +			   "split-event-channels", "%u",

We don't want to call them 'feature-split-event-channels' ?

> +			   &split_evtchn);
> +	if (err < 0)
> +		split_evtchn = 0;
> +
> +	err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
>  			   "max-tx-ring-page-order", "%u",
>  			   &max_tx_ring_page_order);
>  	if (err < 0) {
> @@ -1589,20 +1615,59 @@ static int setup_netfront(struct xenbus_device *dev, struct netfront_info *info)
>  		info->rx_ring_ref[j] = err;
>  	}
>  
> -	err = xenbus_alloc_evtchn(dev, &info->evtchn);
> -	if (err)
> -		goto alloc_evtchn_fail;
> +	if (!split_evtchn) {

Why not just move most of the code that deals with this
allocation in two seperate functions: setup_netfront_split
and setup_netfront_generic ?

> +		err = xenbus_alloc_evtchn(dev, &info->tx_evtchn);
> +		if (err)
> +			goto alloc_evtchn_fail;
>  
> -	err = bind_evtchn_to_irqhandler(info->evtchn, xennet_interrupt,
> -					0, netdev->name, netdev);
> -	if (err < 0)
> -		goto bind_fail;
> -	netdev->irq = err;
> +		err = bind_evtchn_to_irqhandler(info->tx_evtchn,
> +						xennet_interrupt,
> +						0, netdev->name, info);
> +		if (err < 0)
> +			goto bind_fail;
> +		info->rx_evtchn = info->tx_evtchn;
> +		info->tx_irq = info->rx_irq = err;
> +		info->split_evtchn = 0;
> +		dev_info(&dev->dev, "single event channel, irq = %d\n",
> +			 info->tx_irq);
> +	} else {
> +		err = xenbus_alloc_evtchn(dev, &info->tx_evtchn);
> +		if (err)
> +			goto alloc_evtchn_fail;
> +		err = xenbus_alloc_evtchn(dev, &info->rx_evtchn);
> +		if (err) {
> +			xenbus_free_evtchn(dev, info->tx_evtchn);
> +			goto alloc_evtchn_fail;
> +		}
> +		err = bind_evtchn_to_irqhandler(info->tx_evtchn,
> +						xennet_tx_interrupt,
> +						0, netdev->name, info);
> +		if (err < 0)
> +			goto bind_fail;
> +		info->tx_irq = err;
> +		err = bind_evtchn_to_irqhandler(info->rx_evtchn,
> +						xennet_rx_interrupt,
> +						0, netdev->name, info);
> +		if (err < 0) {
> +			unbind_from_irqhandler(info->tx_irq, info);
> +			goto bind_fail;
> +		}
> +		info->rx_irq = err;
> +		info->split_evtchn = 1;
> +		dev_info(&dev->dev, "split event channels,"
> +			 " tx_irq = %d, rx_irq = %d\n",
> +			 info->tx_irq, info->rx_irq);
> +	}
>  
>  	return 0;
>  
>  bind_fail:
> -	xenbus_free_evtchn(dev, info->evtchn);
> +	if (!split_evtchn)
> +		xenbus_free_evtchn(dev, info->tx_evtchn);
> +	else {
> +		xenbus_free_evtchn(dev, info->tx_evtchn);
> +		xenbus_free_evtchn(dev, info->rx_evtchn);
> +	}
>  alloc_evtchn_fail:
>  	for (; j >= 0; j--) {
>  		int ref = info->rx_ring_ref[j];
> @@ -1690,11 +1755,27 @@ again:
>  		}
>  	}
>  
> -	err = xenbus_printf(xbt, dev->nodename,
> -			    "event-channel", "%u", info->evtchn);
> -	if (err) {
> -		message = "writing event-channel";
> -		goto abort_transaction;
> +
> +	if (!info->split_evtchn) {
> +		err = xenbus_printf(xbt, dev->nodename,
> +				    "event-channel", "%u", info->tx_evtchn);
> +		if (err) {
> +			message = "writing event-channel";
> +			goto abort_transaction;
> +		}
> +	} else {
> +		err = xenbus_printf(xbt, dev->nodename,
> +				    "event-channel-tx", "%u", info->tx_evtchn);
> +		if (err) {
> +			message = "writing event-channel-tx";
> +			goto abort_transaction;
> +		}
> +		err = xenbus_printf(xbt, dev->nodename,
> +				    "event-channel-rx", "%u", info->rx_evtchn);
> +		if (err) {
> +			message = "writing event-channel-rx";
> +			goto abort_transaction;
> +		}
>  	}
>  
>  	err = xenbus_printf(xbt, dev->nodename, "request-rx-copy", "%u",
> @@ -1808,7 +1889,9 @@ static int xennet_connect(struct net_device *dev)
>  	 * packets.
>  	 */
>  	netif_carrier_on(np->netdev);
> -	notify_remote_via_irq(np->netdev->irq);
> +	notify_remote_via_irq(np->tx_irq);
> +	if (np->split_evtchn)
> +		notify_remote_via_irq(np->rx_irq);
>  	xennet_tx_buf_gc(dev);
>  	xennet_alloc_rx_buffers(dev);
>  
> -- 
> 1.7.2.5
> 
> 
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