linux-kernel - Re: [PATCH v6 05/18] xen/pvcalls: connect to a frontend

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Date:   Wed, 5 Jul 2017 13:29:52 -0700 (PDT)
From:   Stefano Stabellini <sstabellini@...nel.org>
To:     Juergen Gross <jgross@...e.com>
cc:     Stefano Stabellini <sstabellini@...nel.org>,
        xen-devel@...ts.xen.org, linux-kernel@...r.kernel.org,
        boris.ostrovsky@...cle.com,
        Stefano Stabellini <stefano@...reto.com>
Subject: Re: [PATCH v6 05/18] xen/pvcalls: connect to a frontend

On Tue, 4 Jul 2017, Juergen Gross wrote:
> On 03/07/17 23:08, Stefano Stabellini wrote:
> > Introduce a per-frontend data structure named pvcalls_fedata. 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 also has an unbound workqueue to schedule the work of parsing and
> > executing commands on the command ring. socket_lock protects the two
> > lists. In pvcalls_back_global, keep a list of connected frontends.
> > 
> > Signed-off-by: Stefano Stabellini <stefano@...reto.com>
> > Reviewed-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> > CC: boris.ostrovsky@...cle.com
> > CC: jgross@...e.com
> > ---
> >  drivers/xen/pvcalls-back.c | 92 ++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 92 insertions(+)
> > 
> > diff --git a/drivers/xen/pvcalls-back.c b/drivers/xen/pvcalls-back.c
> > index 7bce750..e4c2e46 100644
> > --- a/drivers/xen/pvcalls-back.c
> > +++ b/drivers/xen/pvcalls-back.c
> > @@ -33,9 +33,101 @@ struct pvcalls_back_global {
> >  	struct semaphore frontends_lock;
> >  } pvcalls_back_global;
> >  
> > +/*
> > + * Per-frontend data structure. It contains pointers to the command
> > + * ring, its event channel, a list of active sockets and a tree of
> > + * passive sockets.
> > + */
> > +struct pvcalls_fedata {
> > +	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 semaphore socket_lock;
> > +	struct workqueue_struct *wq;
> > +	struct work_struct register_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;
> > +	struct pvcalls_fedata *fedata = NULL;
> > +
> > +	fedata = kzalloc(sizeof(struct pvcalls_fedata), GFP_KERNEL);
> > +	if (!fedata)
> > +		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 = bind_interdomain_evtchn_to_irqhandler(dev->otherend_id, evtchn,
> > +						    pvcalls_back_event, 0,
> > +						    "pvcalls-backend", dev);
> > +	if (err < 0)
> > +		goto error;
> > +	fedata->irq = err;
> > +
> > +	fedata->wq = alloc_workqueue("pvcalls_back_wq", WQ_UNBOUND, 1);
> > +	if (!fedata->wq) {
> > +		err = -ENOMEM;
> > +		goto error;
> > +	}
> > +
> > +	err = xenbus_map_ring_valloc(dev, &ring_ref, 1, (void**)&fedata->sring);
> > +	if (err < 0)
> > +		goto error;
> > +
> > +	BACK_RING_INIT(&fedata->ring, fedata->sring, XEN_PAGE_SIZE * 1);
> > +	fedata->dev = dev;
> > +
> > +	INIT_WORK(&fedata->register_work, pvcalls_back_work);
> > +	INIT_LIST_HEAD(&fedata->socket_mappings);
> > +	INIT_RADIX_TREE(&fedata->socketpass_mappings, GFP_KERNEL);
> > +	sema_init(&fedata->socket_lock, 1);
> > +	dev_set_drvdata(&dev->dev, fedata);
> > +
> > +	down(&pvcalls_back_global.frontends_lock);
> > +	list_add_tail(&fedata->list, &pvcalls_back_global.frontends);
> > +	up(&pvcalls_back_global.frontends_lock);
> > +	queue_work(fedata->wq, &fedata->register_work);
> > +
> >  	return 0;
> > +
> > + error:
> > +	if (fedata->sring != NULL)
> > +		xenbus_unmap_ring_vfree(dev, fedata->sring);
> > +	if (fedata->wq)
> > +		destroy_workqueue(fedata->wq);
> > +	unbind_from_irqhandler(fedata->irq, dev);
> 
> fedata->irq might have not been set and can be zero here. irq 0 is
> a valid irq, I think.

You are right. IRQs cannot be negative, so I'll add an fedata->irq = -1;
at the beginning of the function and an if (fedata->irq >= 0) here.