Re: [PATCH v10 02/16] s390/vfio-ap: use new AP bus interface to search for queue devices

[Tony Krowiak]

On 9/24/20 10:27 PM, Halil Pasic wrote:
> On Fri, 21 Aug 2020 15:56:02 -0400
> Tony Krowiak <akrowiak@xxxxxxxxxxxxx> wrote:
>
> > --- a/drivers/s390/crypto/vfio_ap_ops.c
> > +++ b/drivers/s390/crypto/vfio_ap_ops.c
> > @@ -26,43 +26,26 @@
> >   
> >   static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev);
> >   
> > -static int match_apqn(struct device *dev, const void *data)
> > -{
> > -	struct vfio_ap_queue *q = dev_get_drvdata(dev);
> > -
> > -	return (q->apqn == *(int *)(data)) ? 1 : 0;
> > -}
> > -
> >   /**
> > - * vfio_ap_get_queue: Retrieve a queue with a specific APQN from a list
> > - * @matrix_mdev: the associated mediated matrix
> > + * vfio_ap_get_queue: Retrieve a queue with a specific APQN.
> >    * @apqn: The queue APQN
> >    *
> > - * Retrieve a queue with a specific APQN from the list of the
> > - * devices of the vfio_ap_drv.
> > - * Verify that the APID and the APQI are set in the matrix.
> > + * Retrieve a queue with a specific APQN from the AP queue devices attached to
> > + * the AP bus.
> >    *
> > - * Returns the pointer to the associated vfio_ap_queue
> > + * Returns the pointer to the vfio_ap_queue with the specified APQN, or NULL.
> >    */
> > -static struct vfio_ap_queue *vfio_ap_get_queue(
> > -					struct ap_matrix_mdev *matrix_mdev,
> > -					int apqn)
> > +static struct vfio_ap_queue *vfio_ap_get_queue(unsigned long apqn)
> >   {
> > +	struct ap_queue *queue;
> >   	struct vfio_ap_queue *q;
> > -	struct device *dev;
> >   
> > -	if (!test_bit_inv(AP_QID_CARD(apqn), matrix_mdev->matrix.apm))
> > -		return NULL;
> > -	if (!test_bit_inv(AP_QID_QUEUE(apqn), matrix_mdev->matrix.aqm))
> > +	queue = ap_get_qdev(apqn);
> > +	if (!queue)
> >   		return NULL;
> >   
> > -	dev = driver_find_device(&matrix_dev->vfio_ap_drv->driver, NULL,
> > -				 &apqn, match_apqn);
> > -	if (!dev)
> > -		return NULL;
> > -	q = dev_get_drvdata(dev);
> > -	q->matrix_mdev = matrix_mdev;
> > -	put_device(dev);
> > +	q = dev_get_drvdata(&queue->ap_dev.device);
> Is this cast here safe? (I don't think it is.)

In the probe, we execute:
dev_set_drvdata(&queue->ap_dev.device, q);

I don't get any compile nor execution errors. Why wouldn't it be safe?

> > +	put_device(&queue->ap_dev.device);
> >   
> >   	return q;
> >   }