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    SubjectRe: [PATCH 05/18] xen/pvcalls: connect to a frontend
    On Mon, 15 May 2017, Boris Ostrovsky wrote:
    > On 05/15/2017 04:35 PM, Stefano Stabellini wrote:
    > > Introduce a per-frontend data structure named pvcalls_back_priv. It
    > > contains pointers to the command ring, its event channel, a list of
    > > active sockets and a tree of passive sockets (passing sockets need to be
    > > looked up from the id on listen, accept and poll commands, while active
    > > sockets only on release).
    >
    > It would be useful to put this into a comment in pvcalls_back_priv definition.

    I'll do that.


    > > It also has an unbound workqueue to schedule the work of parsing and
    > > executing commands on the command ring. pvcallss_lock protects the two
    > > lists. In pvcalls_back_global, keep a list of connected frontends.
    > >
    > > Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
    > > CC: boris.ostrovsky@oracle.com
    > > CC: jgross@suse.com
    > > ---
    > > drivers/xen/pvcalls-back.c | 87
    > > ++++++++++++++++++++++++++++++++++++++++++++++
    > > 1 file changed, 87 insertions(+)
    > >
    > > diff --git a/drivers/xen/pvcalls-back.c b/drivers/xen/pvcalls-back.c
    > > index 86eca19..876e577 100644
    > > --- a/drivers/xen/pvcalls-back.c
    > > +++ b/drivers/xen/pvcalls-back.c
    > > @@ -44,13 +44,100 @@ struct pvcalls_back_global {
    > > struct rw_semaphore privs_lock;
    > > } pvcalls_back_global;
    > >
    > > +struct pvcalls_back_priv {
    > > + struct list_head list;
    > > + struct xenbus_device *dev;
    > > + struct xen_pvcalls_sring *sring;
    > > + struct xen_pvcalls_back_ring ring;
    > > + int irq;
    > > + struct list_head socket_mappings;
    > > + struct radix_tree_root socketpass_mappings;
    > > + struct rw_semaphore pvcallss_lock;
    >
    > Same question as before regarding using rw semaphore --- I only see
    > down/up_writes.

    And again, you are right. I'll switch it to a regular semaphore.


    > And what does the name (pvcallss) stand for?
    >
    >
    > > + atomic_t work;
    > > + struct workqueue_struct *wq;
    > > + struct work_struct register_work;
    > > +};
    > > +
    > > static void pvcalls_back_ioworker(struct work_struct *work)
    > > {
    > > }
    > >
    > > +static void pvcalls_back_work(struct work_struct *work)
    > > +{
    > > +}
    > > +
    > > +static irqreturn_t pvcalls_back_event(int irq, void *dev_id)
    > > +{
    > > + return IRQ_HANDLED;
    > > +}
    > > +
    > > static int backend_connect(struct xenbus_device *dev)
    > > {
    > > + int err, evtchn;
    > > + grant_ref_t ring_ref;
    > > + void *addr = NULL;
    > > + struct pvcalls_back_priv *priv = NULL;
    > > +
    > > + priv = kzalloc(sizeof(struct pvcalls_back_priv), GFP_KERNEL);
    > > + if (!priv)
    > > + return -ENOMEM;
    > > +
    > > + err = xenbus_scanf(XBT_NIL, dev->otherend, "port", "%u",
    > > + &evtchn);
    > > + if (err != 1) {
    > > + err = -EINVAL;
    > > + xenbus_dev_fatal(dev, err, "reading %s/event-channel",
    > > + dev->otherend);
    > > + goto error;
    > > + }
    > > +
    > > + err = xenbus_scanf(XBT_NIL, dev->otherend, "ring-ref", "%u",
    > > &ring_ref);
    > > + if (err != 1) {
    > > + err = -EINVAL;
    > > + xenbus_dev_fatal(dev, err, "reading %s/ring-ref",
    > > + dev->otherend);
    > > + goto error;
    > > + }
    > > +
    > > + err = xenbus_map_ring_valloc(dev, &ring_ref, 1, &addr);
    > > + if (err < 0)
    > > + goto error;
    >
    >
    > I'd move this closer to first use, below.

    Sure


    > > +
    > > + err = bind_interdomain_evtchn_to_irqhandler(dev->otherend_id, evtchn,
    > > + pvcalls_back_event, 0,
    > > + "pvcalls-backend", dev);
    > > + if (err < 0)
    > > + goto error;
    > > +
    > > + priv->wq = alloc_workqueue("pvcalls_back_wq", WQ_UNBOUND, 1);
    > > + if (!priv->wq) {
    > > + err = -ENOMEM;
    > > + goto error;
    > > + }
    > > + INIT_WORK(&priv->register_work, pvcalls_back_work);
    > > + priv->dev = dev;
    > > + priv->sring = addr;
    > > + BACK_RING_INIT(&priv->ring, priv->sring, XEN_PAGE_SIZE * 1);
    > > + priv->irq = err;
    > > + INIT_LIST_HEAD(&priv->socket_mappings);
    > > + INIT_RADIX_TREE(&priv->socketpass_mappings, GFP_KERNEL);
    > > + init_rwsem(&priv->pvcallss_lock);
    > > + dev_set_drvdata(&dev->dev, priv);
    > > + down_write(&pvcalls_back_global.privs_lock);
    > > + list_add_tail(&priv->list, &pvcalls_back_global.privs);
    > > + up_write(&pvcalls_back_global.privs_lock);
    > > + queue_work(priv->wq, &priv->register_work);
    > > +
    > > return 0;
    > > +
    > > + error:
    > > + if (addr != NULL)
    > > + xenbus_unmap_ring_vfree(dev, addr);
    > > + if (priv->wq)
    > > + destroy_workqueue(priv->wq);
    > > + unbind_from_irqhandler(priv->irq, dev);
    > > + kfree(priv);
    > > + return err;
    > > }
    > >
    > > static int backend_disconnect(struct xenbus_device *dev)
    > >
    >

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