Re: [PATCH v5 2/7] s390: ap: new vfio_ap_queue structure

[Pierre Morel]

On 15/03/2019 11:33, Cornelia Huck wrote:
> On Wed, 13 Mar 2019 17:04:59 +0100
> Pierre Morel <pmorel@xxxxxxxxxxxxx> wrote:
>
> > diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
> > index e9824c3..df6f21a 100644
> > --- a/drivers/s390/crypto/vfio_ap_drv.c
> > +++ b/drivers/s390/crypto/vfio_ap_drv.c
> > @@ -40,14 +40,42 @@ static struct ap_device_id ap_queue_ids[] = {
> >   
> >   MODULE_DEVICE_TABLE(vfio_ap, ap_queue_ids);
> >   
> > +/**
> > + * vfio_ap_queue_dev_probe:
> > + *
> > + * Allocate a vfio_ap_queue structure and associate it
> > + * with the device as driver_data.
> > + */
> >   static int vfio_ap_queue_dev_probe(struct ap_device *apdev)
> >   {
> > +	struct vfio_ap_queue *q;
> > +
> > +	q = kzalloc(sizeof(*q), GFP_KERNEL);
> > +	if (!q)
> > +		return -ENOMEM;
> > +	dev_set_drvdata(&apdev->device, q);
> > +	q->apqn = to_ap_queue(&apdev->device)->qid;
> > +	INIT_LIST_HEAD(&q->list);
> > +	mutex_lock(&matrix_dev->lock);
> > +	list_add(&q->list, &matrix_dev->free_list);
> > +	mutex_unlock(&matrix_dev->lock);
>
>  From what I can see, dealing with the free_list is supposed to be
> protected by the matrix_dev mutex, and at a glance, it indeed seems to
> be held every time you interact with the list. I think it would be good
> to document that with a comment.

Yes.
It is a big lock but only on administrative tasks so I think it is harmless.

> (I have not reviewed this deeply, and I won't be able to look at this
> more until April, sorry.)

OK.
Thanks for the comments.

Regards,
Pierre


--
Pierre Morel
Linux/KVM/QEMU in BÃblingen - Germany