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

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Date:   Mon, 15 May 2017 21:52:02 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Stefano Stabellini <sstabellini@...nel.org>,
        xen-devel@...ts.xen.org
Cc:     linux-kernel@...r.kernel.org, jgross@...e.com,
        Stefano Stabellini <stefano@...reto.com>
Subject: Re: [PATCH 05/18] xen/pvcalls: connect to a frontend



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.

>
> 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@...reto.com>
> CC: boris.ostrovsky@...cle.com
> CC: jgross@...e.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 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.

-boris

> +
> +	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)
>