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

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Date:   Tue, 4 Jul 2017 08:59:09 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Stefano Stabellini <sstabellini@...nel.org>,
        xen-devel@...ts.xen.org
Cc:     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 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.


Juergen