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Date: Tue, 31 Jan 2012 11:57:02 +0000
From: Wei Liu <wei.liu2@...rix.com>
To: Ian Campbell <Ian.Campbell@...rix.com>
CC: <wei.liu2@...rix.com>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
"konrad.wilk@...cle.com" <konrad.wilk@...cle.com>
Subject: Re: [RFC PATCH V3 14/16] netback: split event channels support
On Tue, 2012-01-31 at 10:37 +0000, Ian Campbell wrote:
> O
>
> Can you get rid of split_irq by setting tx_irq == rx_irq in that case
> and simplify the code by doing so?
>
> I think this should work even for places like:
>
> if (!vif->split_irq)
> enable_irq(vif->tx_irq);
> else {
> enable_irq(vif->tx_irq);
> enable_irq(vif->rx_irq);
> }
>
> Just by doing
> enable_irq(vif->tx_irq);
> enable_irq(vif->rx_irq);
>
> Since enable/disable_irq maintain a count and so it will do the right
> thing if they happen to be the same.
>
Hmm... OK.
> > /* The shared tx ring and index. */
> > struct xen_netif_tx_back_ring tx;
> > @@ -162,7 +164,8 @@ struct xenvif *xenvif_alloc(struct device *parent,
> > int xenvif_connect(struct xenvif *vif,
> > unsigned long tx_ring_ref[], unsigned int tx_ring_order,
> > unsigned long rx_ring_ref[], unsigned int rx_ring_order,
> > - unsigned int evtchn, unsigned int rx_protocol);
> > + unsigned int evtchn[], int split_evtchn,
> > + unsigned int rx_protocol);
> > void xenvif_disconnect(struct xenvif *vif);
> >
> > int xenvif_xenbus_init(void);
> > diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
> > index 0f05f03..afccd5d 100644
> > --- a/drivers/net/xen-netback/interface.c
> > +++ b/drivers/net/xen-netback/interface.c
> > @@ -46,15 +46,31 @@ int xenvif_schedulable(struct xenvif *vif)
> > return netif_running(vif->dev) && netif_carrier_ok(vif->dev);
> > }
> >
> > -static irqreturn_t xenvif_interrupt(int irq, void *dev_id)
> > +static irqreturn_t xenvif_tx_interrupt(int irq, void *dev_id)
> > +{
> > + struct xenvif *vif = dev_id;
> > +
> > + if (RING_HAS_UNCONSUMED_REQUESTS(&vif->tx))
> > + napi_schedule(&vif->napi);
> > +
> > + return IRQ_HANDLED;
> > +}
> > +
> > +static irqreturn_t xenvif_rx_interrupt(int irq, void *dev_id)
> > {
> > struct xenvif *vif = dev_id;
> >
> > if (xenvif_schedulable(vif) && vif->event != NULL)
> > vif->event(vif);
> >
> > - if (RING_HAS_UNCONSUMED_REQUESTS(&vif->tx))
> > - napi_schedule(&vif->napi);
> > + return IRQ_HANDLED;
> > +}
> > +
> > +static irqreturn_t xenvif_interrupt(int irq, void *dev_id)
> > +{
> > + xenvif_tx_interrupt(0, dev_id);
>
> Might as well pass irq down.
Sure.
> [...]
> > @@ -308,13 +334,14 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t domid,
> > int xenvif_connect(struct xenvif *vif,
> > unsigned long tx_ring_ref[], unsigned int tx_ring_ref_count,
> > unsigned long rx_ring_ref[], unsigned int rx_ring_ref_count,
> > - unsigned int evtchn, unsigned int rx_protocol)
> > + unsigned int evtchn[], int split_evtchn,
>
> Explicitly tx_evtchn and rx_evtchn would be clearer than remembering
> that [0]==tx and [1]==rx I think.
>
> > + unsigned int rx_protocol)
> > {
> > int err = -ENOMEM;
> > struct xen_netif_tx_sring *txs;
> >
> > /* Already connected through? */
> > - if (vif->irq)
> > + if (vif->tx_irq)
> > return 0;
> >
> > __module_get(THIS_MODULE);
> > @@ -345,13 +372,35 @@ int xenvif_connect(struct xenvif *vif,
> > if (vif->setup(vif))
> > goto err_rx_unmap;
> >
> > - err = bind_interdomain_evtchn_to_irqhandler(
> > - vif->domid, evtchn, xenvif_interrupt, 0,
> > - vif->dev->name, vif);
> > - if (err < 0)
> > - goto err_rx_unmap;
> > - vif->irq = err;
> > - disable_irq(vif->irq);
> > + if (!split_evtchn) {
>
> Presumably this is one of the places where you do have to care about
> split vs non. I did consider whether simply registering two handlers for
> the interrupt in a shared-interrupt style would work, but I think that
> way lies madness and confusion...
>
> > + err = bind_interdomain_evtchn_to_irqhandler(
> > + vif->domid, evtchn[0], xenvif_interrupt, 0,
> > + vif->dev->name, vif);
> > + if (err < 0)
> > + goto err_rx_unmap;
> > + vif->tx_irq = vif->rx_irq = err;
> > + disable_irq(vif->tx_irq);
> > + vif->split_irq = 0;
> > + } else {
> > + err = bind_interdomain_evtchn_to_irqhandler(
> > + vif->domid, evtchn[0], xenvif_tx_interrupt,
> > + 0, vif->dev->name, vif);
> > + if (err < 0)
> > + goto err_rx_unmap;
> > + vif->tx_irq = err;
> > + disable_irq(vif->tx_irq);
> > +
> > + err = bind_interdomain_evtchn_to_irqhandler(
> > + vif->domid, evtchn[1], xenvif_rx_interrupt,
> > + 0, vif->dev->name, vif);
> > + if (err < 0) {
> > + unbind_from_irqhandler(vif->tx_irq, vif);
> > + goto err_rx_unmap;
> > + }
> > + vif->rx_irq = err;
> > + disable_irq(vif->rx_irq);
> > + vif->split_irq = 1;
> > + }
> >
> > init_waitqueue_head(&vif->wq);
> > vif->task = kthread_create(xenvif_kthread,
> > diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
> > index 4067286..c5a3b27 100644
> > --- a/drivers/net/xen-netback/xenbus.c
> > +++ b/drivers/net/xen-netback/xenbus.c
> > @@ -131,6 +131,14 @@ static int netback_probe(struct xenbus_device *dev,
> > goto abort_transaction;
> > }
> >
> > + err = xenbus_printf(xbt, dev->nodename,
> > + "split-event-channels",
>
> Usually we use "feature-FOO" as the names for these sorts of nodes.
>
Got it.
> > + "%u", 1);
> > + if (err) {
> > + message = "writing split-event-channels";
> > + goto abort_transaction;
> > + }
> > +
> > err = xenbus_transaction_end(xbt, 0);
> > } while (err == -EAGAIN);
> >
> > @@ -408,7 +416,7 @@ static int connect_rings(struct backend_info *be)
> > {
> > struct xenvif *vif = be->vif;
> > struct xenbus_device *dev = be->dev;
> > - unsigned int evtchn, rx_copy;
> > + unsigned int evtchn[2], split_evtchn, rx_copy;
>
> Another case where I think two vars is better than a small array.
>
> > int err;
> > int val;
> > unsigned long tx_ring_ref[NETBK_MAX_RING_PAGES];
>
Reasonable change.
Wei.
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