From 50ee60611bf0c7328e5cae438ea5c26590f3f747 Mon Sep 17 00:00:00 2001 From: "Andrew J. Bennieston" Date: Wed, 4 Jun 2014 10:30:45 +0100 Subject: [PATCH] xen-netfront: Add support for multiple queues Build on the refactoring of the previous patch to implement multiple queues between xen-netfront and xen-netback. Check XenStore for multi-queue support, and set up the rings and event channels accordingly. Write ring references and event channels to XenStore in a queue hierarchy if appropriate, or flat when using only one queue. Update the xennet_select_queue() function to choose the queue on which to transmit a packet based on the skb hash result. Signed-off-by: Andrew J. Bennieston Acked-by: Wei Liu Reviewed-by: David Vrabel Signed-off-by: David S. Miller --- drivers/net/xen-netfront.c | 170 +++++++++++++++++++++++++++++-------- 1 file changed, 134 insertions(+), 36 deletions(-) diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c index af8cd95ec76b..55bf834d6a8c 100644 --- a/drivers/net/xen-netfront.c +++ b/drivers/net/xen-netfront.c @@ -57,6 +57,12 @@ #include #include +/* Module parameters */ +static unsigned int xennet_max_queues; +module_param_named(max_queues, xennet_max_queues, uint, 0644); +MODULE_PARM_DESC(max_queues, + "Maximum number of queues per virtual interface"); + static const struct ethtool_ops xennet_ethtool_ops; struct netfront_cb { @@ -565,10 +571,22 @@ static int xennet_count_skb_frag_slots(struct sk_buff *skb) return pages; } -static u16 xennet_select_queue(struct net_device *dev, struct sk_buff *skb) +static u16 xennet_select_queue(struct net_device *dev, struct sk_buff *skb, + void *accel_priv, select_queue_fallback_t fallback) { - /* Stub for later implementation of queue selection */ - return 0; + unsigned int num_queues = dev->real_num_tx_queues; + u32 hash; + u16 queue_idx; + + /* First, check if there is only one queue */ + if (num_queues == 1) { + queue_idx = 0; + } else { + hash = skb_get_hash(skb); + queue_idx = hash % num_queues; + } + + return queue_idx; } static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev) @@ -1316,7 +1334,7 @@ static struct net_device *xennet_create_dev(struct xenbus_device *dev) struct net_device *netdev; struct netfront_info *np; - netdev = alloc_etherdev_mq(sizeof(struct netfront_info), 1); + netdev = alloc_etherdev_mq(sizeof(struct netfront_info), xennet_max_queues); if (!netdev) return ERR_PTR(-ENOMEM); @@ -1687,6 +1705,88 @@ static int xennet_init_queue(struct netfront_queue *queue) return err; } +static int write_queue_xenstore_keys(struct netfront_queue *queue, + struct xenbus_transaction *xbt, int write_hierarchical) +{ + /* Write the queue-specific keys into XenStore in the traditional + * way for a single queue, or in a queue subkeys for multiple + * queues. + */ + struct xenbus_device *dev = queue->info->xbdev; + int err; + const char *message; + char *path; + size_t pathsize; + + /* Choose the correct place to write the keys */ + if (write_hierarchical) { + pathsize = strlen(dev->nodename) + 10; + path = kzalloc(pathsize, GFP_KERNEL); + if (!path) { + err = -ENOMEM; + message = "out of memory while writing ring references"; + goto error; + } + snprintf(path, pathsize, "%s/queue-%u", + dev->nodename, queue->id); + } else { + path = (char *)dev->nodename; + } + + /* Write ring references */ + err = xenbus_printf(*xbt, path, "tx-ring-ref", "%u", + queue->tx_ring_ref); + if (err) { + message = "writing tx-ring-ref"; + goto error; + } + + err = xenbus_printf(*xbt, path, "rx-ring-ref", "%u", + queue->rx_ring_ref); + if (err) { + message = "writing rx-ring-ref"; + goto error; + } + + /* Write event channels; taking into account both shared + * and split event channel scenarios. + */ + if (queue->tx_evtchn == queue->rx_evtchn) { + /* Shared event channel */ + err = xenbus_printf(*xbt, path, + "event-channel", "%u", queue->tx_evtchn); + if (err) { + message = "writing event-channel"; + goto error; + } + } else { + /* Split event channels */ + err = xenbus_printf(*xbt, path, + "event-channel-tx", "%u", queue->tx_evtchn); + if (err) { + message = "writing event-channel-tx"; + goto error; + } + + err = xenbus_printf(*xbt, path, + "event-channel-rx", "%u", queue->rx_evtchn); + if (err) { + message = "writing event-channel-rx"; + goto error; + } + } + + if (write_hierarchical) + kfree(path); + return 0; + +error: + if (write_hierarchical) + kfree(path); + xenbus_dev_fatal(dev, err, "%s", message); + return err; +} + /* Common code used when first setting up, and when resuming. */ static int talk_to_netback(struct xenbus_device *dev, struct netfront_info *info) @@ -1696,11 +1796,19 @@ static int talk_to_netback(struct xenbus_device *dev, int err; unsigned int feature_split_evtchn; unsigned int i = 0; + unsigned int max_queues = 0; struct netfront_queue *queue = NULL; unsigned int num_queues = 1; info->netdev->irq = 0; + /* Check if backend supports multiple queues */ + err = xenbus_scanf(XBT_NIL, info->xbdev->otherend, + "multi-queue-max-queues", "%u", &max_queues); + if (err < 0) + max_queues = 1; + num_queues = min(max_queues, xennet_max_queues); + /* Check feature-split-event-channels */ err = xenbus_scanf(XBT_NIL, info->xbdev->otherend, "feature-split-event-channels", "%u", @@ -1765,49 +1873,35 @@ static int talk_to_netback(struct xenbus_device *dev, } again: - queue = &info->queues[0]; /* Use first queue only */ - err = xenbus_transaction_start(&xbt); if (err) { xenbus_dev_fatal(dev, err, "starting transaction"); goto destroy_ring; } - err = xenbus_printf(xbt, dev->nodename, "tx-ring-ref", "%u", - queue->tx_ring_ref); - if (err) { - message = "writing tx ring-ref"; - goto abort_transaction; - } - err = xenbus_printf(xbt, dev->nodename, "rx-ring-ref", "%u", - queue->rx_ring_ref); - if (err) { - message = "writing rx ring-ref"; - goto abort_transaction; - } - - if (queue->tx_evtchn == queue->rx_evtchn) { - err = xenbus_printf(xbt, dev->nodename, - "event-channel", "%u", queue->tx_evtchn); - if (err) { - message = "writing event-channel"; - goto abort_transaction; - } + if (num_queues == 1) { + err = write_queue_xenstore_keys(&info->queues[0], &xbt, 0); /* flat */ + if (err) + goto abort_transaction_no_dev_fatal; } else { - err = xenbus_printf(xbt, dev->nodename, - "event-channel-tx", "%u", queue->tx_evtchn); + /* Write the number of queues */ + err = xenbus_printf(xbt, dev->nodename, "multi-queue-num-queues", + "%u", num_queues); if (err) { - message = "writing event-channel-tx"; - goto abort_transaction; + message = "writing multi-queue-num-queues"; + goto abort_transaction_no_dev_fatal; } - err = xenbus_printf(xbt, dev->nodename, - "event-channel-rx", "%u", queue->rx_evtchn); - if (err) { - message = "writing event-channel-rx"; - goto abort_transaction; + + /* Write the keys for each queue */ + for (i = 0; i < num_queues; ++i) { + queue = &info->queues[i]; + err = write_queue_xenstore_keys(queue, &xbt, 1); /* hierarchical */ + if (err) + goto abort_transaction_no_dev_fatal; } } + /* The remaining keys are not queue-specific */ err = xenbus_printf(xbt, dev->nodename, "request-rx-copy", "%u", 1); if (err) { @@ -1857,8 +1951,9 @@ again: return 0; abort_transaction: - xenbus_transaction_end(xbt, 1); xenbus_dev_fatal(dev, err, "%s", message); +abort_transaction_no_dev_fatal: + xenbus_transaction_end(xbt, 1); destroy_ring: xennet_disconnect_backend(info); kfree(info->queues); @@ -2264,6 +2359,9 @@ static int __init netif_init(void) pr_info("Initialising Xen virtual ethernet driver\n"); + /* Allow as many queues as there are CPUs, by default */ + xennet_max_queues = num_online_cpus(); + return xenbus_register_frontend(&netfront_driver); } module_init(netif_init); -- 2.30.2