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Date: Mon, 24 Feb 2014 14:58:05 +0000
From: Paul Durrant <Paul.Durrant@...rix.com>
To: Andrew Bennieston <andrew.bennieston@...rix.com>,
"xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>
CC: Ian Campbell <Ian.Campbell@...rix.com>,
Wei Liu <wei.liu2@...rix.com>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
Andrew Bennieston <andrew.bennieston@...rix.com>
Subject: RE: [PATCH V5 net-next 2/5] xen-netback: Add support for multiple
queues
> -----Original Message-----
> From: Andrew J. Bennieston [mailto:andrew.bennieston@...rix.com]
> Sent: 24 February 2014 14:33
> To: xen-devel@...ts.xenproject.org
> Cc: Ian Campbell; Wei Liu; Paul Durrant; netdev@...r.kernel.org; Andrew
> Bennieston
> Subject: [PATCH V5 net-next 2/5] xen-netback: Add support for multiple
> queues
>
> From: "Andrew J. Bennieston" <andrew.bennieston@...rix.com>
>
> Builds on the refactoring of the previous patch to implement multiple
> queues between xen-netfront and xen-netback.
>
> Writes the maximum supported number of queues into XenStore, and reads
> the values written by the frontend to determine how many queues to use.
>
> Ring references and event channels are read from XenStore on a per-queue
> basis and rings are connected accordingly.
>
> Signed-off-by: Andrew J. Bennieston <andrew.bennieston@...rix.com>
Reviewed-by: Paul Durrant <paul.durrant@...rix.com>
> ---
> drivers/net/xen-netback/common.h | 2 +
> drivers/net/xen-netback/interface.c | 7 +++-
> drivers/net/xen-netback/netback.c | 8 ++++
> drivers/net/xen-netback/xenbus.c | 76
> ++++++++++++++++++++++++++++++-----
> 4 files changed, 82 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-
> netback/common.h
> index 4176539..e72bf38 100644
> --- a/drivers/net/xen-netback/common.h
> +++ b/drivers/net/xen-netback/common.h
> @@ -261,4 +261,6 @@ void xenvif_carrier_on(struct xenvif *vif);
>
> extern bool separate_tx_rx_irq;
>
> +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 0297980..3f623b4 100644
> --- a/drivers/net/xen-netback/interface.c
> +++ b/drivers/net/xen-netback/interface.c
> @@ -381,7 +381,12 @@ 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);
> 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 a32abd6..9849b63 100644
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -54,6 +54,11 @@
> bool separate_tx_rx_irq = 1;
> module_param(separate_tx_rx_irq, bool, 0644);
>
> +unsigned int xenvif_max_queues;
> +module_param(xenvif_max_queues, uint, 0644);
> +MODULE_PARM_DESC(xenvif_max_queues,
> + "Maximum number of queues per virtual interface");
> +
> /*
> * This is the maximum slots a skb can have. If a guest sends a skb
> * which exceeds this limit it is considered malicious.
> @@ -1585,6 +1590,9 @@ static int __init netback_init(void)
> if (!xen_domain())
> return -ENODEV;
>
> + /* Allow as many queues as there are CPUs, by default */
> + xenvif_max_queues = num_online_cpus();
> +
> if (fatal_skb_slots < XEN_NETBK_LEGACY_SLOTS_MAX) {
> pr_info("fatal_skb_slots too small (%d), bump it to
> XEN_NETBK_LEGACY_SLOTS_MAX (%d)\n",
> fatal_skb_slots, XEN_NETBK_LEGACY_SLOTS_MAX);
> diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-
> netback/xenbus.c
> index f23ea0a..c1ae148 100644
> --- a/drivers/net/xen-netback/xenbus.c
> +++ b/drivers/net/xen-netback/xenbus.c
> @@ -20,6 +20,7 @@
>
> #include "common.h"
> #include <linux/vmalloc.h>
> +#include <linux/rtnetlink.h>
>
> struct backend_info {
> struct xenbus_device *dev;
> @@ -159,6 +160,12 @@ static int netback_probe(struct xenbus_device *dev,
> if (err)
> pr_debug("Error writing feature-split-event-channels\n");
>
> + /* Multi-queue support: This is an optional feature. */
> + err = xenbus_printf(XBT_NIL, dev->nodename,
> + "multi-queue-max-queues", "%u",
> xenvif_max_queues);
> + if (err)
> + pr_debug("Error writing multi-queue-max-queues\n");
> +
> err = xenbus_switch_state(dev, XenbusStateInitWait);
> if (err)
> goto fail;
> @@ -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);
> + return;
> + }
>
> err = xen_net_read_mac(dev, be->vif->fe_dev_addr);
> if (err) {
> @@ -500,9 +524,13 @@ static void connect(struct backend_info *be)
> xen_net_read_rate(dev, &credit_bytes, &credit_usec);
> read_xenbus_vif_flags(be);
>
> - be->vif->num_queues = 1;
> + /* Use the number of queues requested by the frontend */
> + be->vif->num_queues = requested_num_queues;
> be->vif->queues = vzalloc(be->vif->num_queues *
> sizeof(struct xenvif_queue));
> + rtnl_lock();
> + netif_set_real_num_tx_queues(be->vif->dev, be->vif-
> >num_queues);
> + rtnl_unlock();
>
> for (queue_index = 0; queue_index < be->vif->num_queues;
> ++queue_index) {
> queue = &be->vif->queues[queue_index];
> @@ -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;
> + 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;
> + } else {
> + xspathsize = strlen(dev->otherend) +
> xenstore_path_ext_size;
> + xspath = kzalloc(xspathsize, GFP_KERNEL);
> + if (!xspath) {
> + xenbus_dev_fatal(dev, -ENOMEM,
> + "reading ring references");
> + return -ENOMEM;
> + }
> + snprintf(xspath, xspathsize, "%s/queue-%u", dev-
> >otherend,
> + queue->id);
> + }
>
> - err = xenbus_gather(XBT_NIL, dev->otherend,
> + err = xenbus_gather(XBT_NIL, xspath,
> "tx-ring-ref", "%lu", &tx_ring_ref,
> "rx-ring-ref", "%lu", &rx_ring_ref, NULL);
> if (err) {
> xenbus_dev_fatal(dev, err,
> "reading %s/ring-ref",
> - dev->otherend);
> - return err;
> + xspath);
> + goto err;
> }
>
> /* Try split event channels first, then single event channel. */
> - err = xenbus_gather(XBT_NIL, dev->otherend,
> + err = xenbus_gather(XBT_NIL, xspath,
> "event-channel-tx", "%u", &tx_evtchn,
> "event-channel-rx", "%u", &rx_evtchn, NULL);
> if (err < 0) {
> - err = xenbus_scanf(XBT_NIL, dev->otherend,
> + err = xenbus_scanf(XBT_NIL, xspath,
> "event-channel", "%u", &tx_evtchn);
> if (err < 0) {
> xenbus_dev_fatal(dev, err,
> "reading %s/event-channel(-tx/rx)",
> - dev->otherend);
> - return err;
> + xspath);
> + goto err;
> }
> rx_evtchn = tx_evtchn;
> }
> @@ -582,10 +633,15 @@ static int connect_rings(struct backend_info *be,
> struct xenvif_queue *queue)
> "mapping shared-frames %lu/%lu port tx %u
> rx %u",
> tx_ring_ref, rx_ring_ref,
> tx_evtchn, rx_evtchn);
> - return err;
> + goto err;
> }
>
> - return 0;
> + err = 0;
> +err: /* Regular return falls through with err == 0 */
> + if (xspath != dev->otherend)
> + kfree(xspath);
> +
> + return err;
> }
>
> static int read_xenbus_vif_flags(struct backend_info *be)
> --
> 1.7.10.4
--
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