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Date: Wed, 22 May 2013 11:40:41 -0400
From: annie li <annie.li@...cle.com>
To: Wei Liu <wei.liu2@...rix.com>
CC: xen-devel@...ts.xen.org, netdev@...r.kernel.org,
ian.campbell@...rix.com, konrad.wilk@...cle.com,
david.vrabel@...rix.com
Subject: Re: [PATCH net-next V2 1/2] xen-netback: split event channels support
for Xen backend driver
On 2013-5-21 14:35, Wei Liu wrote:
> [....]
> +
> static int xenvif_start_xmit(struct sk_buff *skb, struct net_device *dev)
> {
> struct xenvif *vif = netdev_priv(dev);
> @@ -125,13 +143,15 @@ static struct net_device_stats *xenvif_get_stats(struct net_device *dev)
> static void xenvif_up(struct xenvif *vif)
> {
> xen_netbk_add_xenvif(vif);
> - enable_irq(vif->irq);
> + enable_irq(vif->tx_irq);
> + enable_irq(vif->rx_irq);
enable_irq are called twice in one event channel situation. How about
adding if condition here to differ one event channel and split event
channel?
> xen_netbk_check_rx_xenvif(vif);
> }
>
> static void xenvif_down(struct xenvif *vif)
> {
> - disable_irq(vif->irq);
> + disable_irq(vif->tx_irq);
> + disable_irq(vif->rx_irq);
Same as enable_irq.
> del_timer_sync(&vif->credit_timeout);
> xen_netbk_deschedule_xenvif(vif);
> xen_netbk_remove_xenvif(vif);
> @@ -308,12 +328,13 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t domid,
> }
>
> int xenvif_connect(struct xenvif *vif, unsigned long tx_ring_ref,
> - unsigned long rx_ring_ref, unsigned int evtchn)
> + unsigned long rx_ring_ref, unsigned int tx_evtchn,
> + unsigned int rx_evtchn)
> {
> int err = -ENOMEM;
>
> /* Already connected through? */
> - if (vif->irq)
> + if (vif->tx_irq)
> return 0;
>
> __module_get(THIS_MODULE);
> @@ -322,13 +343,38 @@ int xenvif_connect(struct xenvif *vif, unsigned long tx_ring_ref,
> if (err < 0)
> goto err;
>
> - err = bind_interdomain_evtchn_to_irqhandler(
> - vif->domid, evtchn, xenvif_interrupt, 0,
> - vif->dev->name, vif);
> - if (err < 0)
> - goto err_unmap;
> - vif->irq = err;
> - disable_irq(vif->irq);
> + if (tx_evtchn == rx_evtchn) {
> + /* feature-split-event-channels == 0 */
> + err = bind_interdomain_evtchn_to_irqhandler(
> + vif->domid, tx_evtchn, xenvif_interrupt, 0,
> + vif->dev->name, vif);
> + if (err < 0)
> + goto err_unmap;
> + vif->tx_irq = vif->rx_irq = err;
> + disable_irq(vif->tx_irq);
> + disable_irq(vif->rx_irq);
Same as above.
> + } else {
> + /* feature-split-event-channels == 1 */
> + snprintf(vif->tx_irq_name, sizeof(vif->tx_irq_name),
> + "%s-tx", vif->dev->name);
> + err = bind_interdomain_evtchn_to_irqhandler(
> + vif->domid, tx_evtchn, xenvif_tx_interrupt, 0,
> + vif->tx_irq_name, vif);
> + if (err < 0)
> + goto err_unmap;
> + vif->tx_irq = err;
> + disable_irq(vif->tx_irq);
> +
> + snprintf(vif->rx_irq_name, sizeof(vif->rx_irq_name),
> + "%s-rx", vif->dev->name);
> + err = bind_interdomain_evtchn_to_irqhandler(
> + vif->domid, rx_evtchn, xenvif_rx_interrupt, 0,
> + vif->rx_irq_name, vif);
> + if (err < 0)
> + goto err_tx_unbind;
> + vif->rx_irq = err;
> + disable_irq(vif->rx_irq);
> + }
>
> xenvif_get(vif);
>
> @@ -342,6 +388,9 @@ int xenvif_connect(struct xenvif *vif, unsigned long tx_ring_ref,
> rtnl_unlock();
>
> return 0;
> +err_tx_unbind:
> + unbind_from_irqhandler(vif->tx_irq, vif);
> + vif->tx_irq = 0;
> err_unmap:
> xen_netbk_unmap_frontend_rings(vif);
> err:
> @@ -375,8 +424,13 @@ void xenvif_disconnect(struct xenvif *vif)
> atomic_dec(&vif->refcnt);
> wait_event(vif->waiting_to_free, atomic_read(&vif->refcnt) == 0);
>
> - if (vif->irq) {
> - unbind_from_irqhandler(vif->irq, vif);
> + if (vif->tx_irq) {
> + if (vif->tx_irq == vif->rx_irq)
> + unbind_from_irqhandler(vif->tx_irq, vif);
> + else {
> + unbind_from_irqhandler(vif->tx_irq, vif);
> + unbind_from_irqhandler(vif->rx_irq, vif);
> + }
> /* vif->irq is valid, we had a module_get in
> * xenvif_connect.
> */
> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
> index 2d9477f..ccfbb74 100644
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -47,6 +47,13 @@
> #include <asm/xen/hypercall.h>
> #include <asm/xen/page.h>
>
> +/* Provide an option to disable split event channels at load time as
> + * event channels are limited resource. Split event channels are
> + * enabled by default.
> + */
> +unsigned int feature_split_event_channels = 1;
> +module_param(feature_split_event_channels, uint, 0644);
> +
> /*
> * This is the maximum slots a skb can have. If a guest sends a skb
> * which exceeds this limit it is considered malicious.
> @@ -662,7 +669,7 @@ static void xen_netbk_rx_action(struct xen_netbk *netbk)
> {
> struct xenvif *vif = NULL, *tmp;
> s8 status;
> - u16 irq, flags;
> + u16 flags;
> struct xen_netif_rx_response *resp;
> struct sk_buff_head rxq;
> struct sk_buff *skb;
> @@ -771,7 +778,6 @@ static void xen_netbk_rx_action(struct xen_netbk *netbk)
> sco->meta_slots_used);
>
> RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&vif->rx, ret);
> - irq = vif->irq;
> if (ret && list_empty(&vif->notify_list))
> list_add_tail(&vif->notify_list, ¬ify);
>
> @@ -783,7 +789,7 @@ static void xen_netbk_rx_action(struct xen_netbk *netbk)
> }
>
> list_for_each_entry_safe(vif, tmp, ¬ify, notify_list) {
> - notify_remote_via_irq(vif->irq);
> + notify_remote_via_irq(vif->rx_irq);
> list_del_init(&vif->notify_list);
> }
>
> @@ -1762,7 +1768,7 @@ static void make_tx_response(struct xenvif *vif,
> vif->tx.rsp_prod_pvt = ++i;
> RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&vif->tx, notify);
> if (notify)
> - notify_remote_via_irq(vif->irq);
> + notify_remote_via_irq(vif->tx_irq);
> }
>
> static struct xen_netif_rx_response *make_rx_response(struct xenvif *vif,
> diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
> index d230c14..461efc6 100644
> --- a/drivers/net/xen-netback/xenbus.c
> +++ b/drivers/net/xen-netback/xenbus.c
> @@ -114,6 +114,15 @@ static int netback_probe(struct xenbus_device *dev,
> goto abort_transaction;
> }
>
> + /* Split event channels support */
> + err = xenbus_printf(xbt, dev->nodename,
> + "feature-split-event-channels",
> + "%u", feature_split_event_channels);
> + if (err) {
> + message = "writing feature-split-event-channels";
> + goto abort_transaction;
> + }
> +
> err = xenbus_transaction_end(xbt, 0);
> } while (err == -EAGAIN);
>
> @@ -393,21 +402,36 @@ static int connect_rings(struct backend_info *be)
> struct xenvif *vif = be->vif;
> struct xenbus_device *dev = be->dev;
> unsigned long tx_ring_ref, rx_ring_ref;
> - unsigned int evtchn, rx_copy;
> + unsigned int tx_evtchn, rx_evtchn, rx_copy;
> int err;
> int val;
>
> err = xenbus_gather(XBT_NIL, dev->otherend,
> "tx-ring-ref", "%lu", &tx_ring_ref,
> - "rx-ring-ref", "%lu", &rx_ring_ref,
> - "event-channel", "%u", &evtchn, NULL);
> + "rx-ring-ref", "%lu", &rx_ring_ref, NULL);
> if (err) {
> xenbus_dev_fatal(dev, err,
> - "reading %s/ring-ref and event-channel",
> + "reading %s/ring-ref",
> dev->otherend);
> return err;
> }
>
> + /* Try split event channels first, then single event channel. */
> + err = xenbus_gather(XBT_NIL, dev->otherend,
> + "event-channel-tx", "%u", &tx_evtchn,
> + "event-channel-rx", "%u", &rx_evtchn, NULL);
> + if (err) {
> + err = xenbus_gather(XBT_NIL, dev->otherend,
> + "event-channel", "%u", &tx_evtchn, NULL);
> + if (err) {
> + xenbus_dev_fatal(dev, err,
> + "reading %s/event-channel(-tx/rx)",
> + dev->otherend);
This err really comes from reading original implementation(one event
channel), right? So it is better to not use (-tx/rx) here?
Or using two xenbus_dev_fatal to print log: one for reading tx/rx
failure, the other for one event channel failure.
Thanks
Annie
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