Re: [PATCH v7 01/15] s390/vfio-ap: store queue struct in hash table for quick access

[Tony Krowiak]

On 4/8/20 12:27 PM, Cornelia Huck wrote:
> On Wed, 8 Apr 2020 11:38:07 -0400
> Tony Krowiak <akrowiak@xxxxxxxxxxxxx> wrote:
>
> > On 4/8/20 6:48 AM, Cornelia Huck wrote:
> > > On Tue,  7 Apr 2020 15:20:01 -0400
> > > Tony Krowiak <akrowiak@xxxxxxxxxxxxx> wrote:
> > >   
> > > > Rather than looping over potentially 65535 objects, let's store the
> > > > structures for caching information about queue devices bound to the
> > > > vfio_ap device driver in a hash table keyed by APQN.
> > > This also looks like a nice code simplification.
> > >   
> > > > Signed-off-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
> > > > ---
> > > >    drivers/s390/crypto/vfio_ap_drv.c     | 28 +++------
> > > >    drivers/s390/crypto/vfio_ap_ops.c     | 90 ++++++++++++++-------------
> > > >    drivers/s390/crypto/vfio_ap_private.h | 10 ++-
> > > >    3 files changed, 60 insertions(+), 68 deletions(-)
> > > >   
> > > (...)
> > > > - */
> > > > -static struct vfio_ap_queue *vfio_ap_get_queue(
> > > > -					struct ap_matrix_mdev *matrix_mdev,
> > > > -					int apqn)
> > > > +struct vfio_ap_queue *vfio_ap_get_queue(unsigned long apqn)
> > > >    {
> > > >    	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))
> > > > -		return NULL;
> > > These were just optimizations and therefore can be dropped now?
> > The purpose of this function has changed from its previous incarnation.
> > This function was originally called from the handle_pqap() function and
> > served two purposes: It retrieved the struct vfio_ap_queue as driver data
> > and linked the matrix_mdev to the vfio_ap_queue. The linking of the
> > matrix_mdev and the vfio_ap_queue are now done when queue devices
> > are probed and when adapters and domains are assigned; so now, the
> > handle_pqap() function calls this function to retrieve both the
> > vfio_ap_queue as well as the matrix_mdev to which it is linked.
> > Consequently,
> > the above code is no longer needed.
> Thanks for the explanation, that makes sense.
>
> > >   
> > > > -
> > > > -	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);
> > > >    
> > > > -	return q;
> > > > +	hash_for_each_possible(matrix_dev->qtable, q, qnode, apqn) {
> > > > +		if (q && (apqn == q->apqn))
> > > > +			return q;
> > > > +	}
> > > Do we need any serialization here? Previously, the driver core made
> > > sure we could get a reference only if the device was still registered;
> > > not sure if we need any further guarantees now.
> > The vfio_ap_queue structs are created when the queue device is
> > probed and removed when the queue device is removed.
> Ok, so anything further is not needed.
>
> > >   
> > > > +
> > > > +	return NULL;
> > > >    }
> > > >    
> > > >    /**
> > > (...)
> > >   
> Looks good to me, then. With vfio_ap_get_queue made static and the
> kerneldoc restored/updated:

Already done, thanks for the review.

> Reviewed-by: Cornelia Huck <cohuck@xxxxxxxxxx>