Re: [PATCH v16 02/14] s390/vfio-ap: use new AP bus interface to search for queue devices

[Tony Krowiak]

On 6/9/21 9:52 AM, Jason J. Herne wrote:
> On 5/10/21 12:44 PM, Tony Krowiak wrote:
> > This patch refactors the vfio_ap device driver to use the AP bus's
> > ap_get_qdev() function to retrieve the vfio_ap_queue struct containing
> > information about a queue that is bound to the vfio_ap device driver.
> > The bus's ap_get_qdev() function retrieves the queue device from a
> > hashtable keyed by APQN. This is much more efficient than looping over
> > the list of devices attached to the AP bus by several orders of
> > magnitude.
> >
> > Signed-off-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
> > Reviewed-by: Halil Pasic <pasic@xxxxxxxxxxxxx>
> > ---
> >   drivers/s390/crypto/vfio_ap_ops.c | 23 +++++++++--------------
> >   1 file changed, 9 insertions(+), 14 deletions(-)
> >
> > diff --git a/drivers/s390/crypto/vfio_ap_ops.c 
> > b/drivers/s390/crypto/vfio_ap_ops.c
> > index 757166da947e..8a50aa650b65 100644
> > --- a/drivers/s390/crypto/vfio_ap_ops.c
> > +++ b/drivers/s390/crypto/vfio_ap_ops.c
> > @@ -27,13 +27,6 @@
> >   static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev);
> >   static struct vfio_ap_queue *vfio_ap_find_queue(int apqn);
> >   -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
> > @@ -1253,15 +1246,17 @@ static int vfio_ap_mdev_group_notifier(struct 
> > notifier_block *nb,
> >     static struct vfio_ap_queue *vfio_ap_find_queue(int apqn)
> >   {
> > -    struct device *dev;
> > +    struct ap_queue *queue;
> >       struct vfio_ap_queue *q = NULL;
>
> The use of q and queue as variable names was a little confusing to me 
> at first. I tried renaming them a few times, the best I could come up 
> with was this:

I am (was) not a fan of the naming convention, but using 'q' to name a 
struct vfio_ap_queue
was introduced (not by me) quite some time ago, so rather than 
introducing a variable name
change at this juncture, I stuck with it to be consistent with the other 
places it is used.

> struct ap_queue *queue;
> struct vfio_ap_queue *vfio_queue = NULL;
>
> Take it or leave it :) Other than that, LGTM.
> Reviewed-by: Jason J. Herne <jjherne@xxxxxxxxxxxxx>

Thanks for your review.

> > -    dev = driver_find_device(&matrix_dev->vfio_ap_drv->driver, NULL,
> > -                 &apqn, match_apqn);
> > -    if (dev) {
> > -        q = dev_get_drvdata(dev);
> > -        put_device(dev);
> > -    }
> > +    queue = ap_get_qdev(apqn);
> > +    if (!queue)
> > +        return NULL;
> > +
> > +    if (queue->ap_dev.device.driver == 
> > &matrix_dev->vfio_ap_drv->driver)
> > +        q = dev_get_drvdata(&queue->ap_dev.device);
> > +
> > +    put_device(&queue->ap_dev.device);
> >         return q;
> >   }