Re: [PATCH v6 2/7] s390: ap: new vfio_ap_queue structure

[Pierre Morel]

On 26/03/2019 21:45, Tony Krowiak wrote:
> On 3/22/19 10:43 AM, Pierre Morel wrote:
> > The AP interruptions are assigned on a queue basis and
> > the GISA structure is handled on a VM basis, so that
> > we need to add a structure we can retrieve from both side
>
> s/side/sides/
OK

> > holding the information we need to handle PQAP/AQIC interception
> > and setup the GISA.
>
> s/setup/set up/

OK

...snip...

> > +
> > +static int vfio_ap_mdev_reset_queue(struct vfio_ap_queue *q)
> > +{
> > +ÂÂÂ struct ap_queue_status status;
> > +ÂÂÂ int retry = 1;
> > +
> > +ÂÂÂ do {
> > +ÂÂÂÂÂÂÂ status = ap_zapq(q->apqn);
> > +ÂÂÂÂÂÂÂ switch (status.response_code) {
> > +ÂÂÂÂÂÂÂ case AP_RESPONSE_NORMAL:
> > +ÂÂÂÂÂÂÂÂÂÂÂ return 0;
> > +ÂÂÂÂÂÂÂ case AP_RESPONSE_RESET_IN_PROGRESS:
> > +ÂÂÂÂÂÂÂ case AP_RESPONSE_BUSY:
> > +ÂÂÂÂÂÂÂÂÂÂÂ msleep(20);
> > +ÂÂÂÂÂÂÂÂÂÂÂ break;
> > +ÂÂÂÂÂÂÂ default:
> > +ÂÂÂÂÂÂÂÂÂÂÂ /* things are really broken, give up */
>
> I'm not sure things are necessarily broken. We could end up here if
> the AP is removed from the configuration via the SE or SCLP Deconfigure
> Adjunct Processor command.

OK, but note that it is your original comment I just moved the function 
here ;)

> > +ÂÂÂÂÂÂÂÂÂÂÂ return -EIO;
> > +ÂÂÂÂÂÂÂ }
> > +ÂÂÂ } while (retry--);
> > +
> > +ÂÂÂ return -EBUSY;
> > +}
> > +
> > Â static void vfio_ap_matrix_init(struct ap_config_info *info,
> > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ struct ap_matrix *matrix)
> > Â {
> > @@ -45,6 +107,7 @@ static int vfio_ap_mdev_create(struct kobject 
> > *kobj, struct mdev_device *mdev)
> > ÂÂÂÂÂÂÂÂÂ return -ENOMEM;
> > ÂÂÂÂÂ }
> > +ÂÂÂ INIT_LIST_HEAD(&matrix_mdev->qlist);
> > ÂÂÂÂÂ vfio_ap_matrix_init(&matrix_dev->info, &matrix_mdev->matrix);
> > ÂÂÂÂÂ mdev_set_drvdata(mdev, matrix_mdev);
> > ÂÂÂÂÂ mutex_lock(&matrix_dev->lock);
> > @@ -113,162 +176,189 @@ static struct attribute_group 
> > *vfio_ap_mdev_type_groups[] = {
> > ÂÂÂÂÂ NULL,
> > Â };
> > -struct vfio_ap_queue_reserved {
> > -ÂÂÂ unsigned long *apid;
> > -ÂÂÂ unsigned long *apqi;
> > -ÂÂÂ bool reserved;
> > -};
> > +static void vfio_ap_free_queue(int apqn, struct ap_matrix_mdev 
> > *matrix_mdev)
> > +{
> > +ÂÂÂ struct vfio_ap_queue *q;
> > +
> > +ÂÂÂ q = vfio_ap_get_queue(apqn, &matrix_mdev->qlist);
> > +ÂÂÂ if (!q)
> > +ÂÂÂÂÂÂÂ return;
> > +ÂÂÂ q->matrix_mdev = NULL;
> > +ÂÂÂ vfio_ap_mdev_reset_queue(q);
>
> I'm wondering if it's necessary to reset the queue here. The only time
> a queue is used is when a guest using the mdev device is started. When
> that guest is terminated, the fd for the mdev device is closed and the
> mdev device's release callback is invoked. The release callback resets
> the queues assigned to the mdev device. Is it really necessary to
> reset the queue again when it is unassigned even if there would have
> been no subsequent activity?

Yes, it is necessary, the queue can be re-assigned to another guest later.
Release will only be called when unbinding the queue from the driver.

> > +ÂÂÂ list_move(&q->list, &matrix_dev->free_list);
> > +}

...snip...

> > +ÂÂÂ for_each_set_bit_inv(apid, matrix_mdev->matrix.apm, AP_DEVICES) {
> > +ÂÂÂÂÂÂÂ apqn = AP_MKQID(apid, apqi);
> > +ÂÂÂÂÂÂÂ q = vfio_ap_find_queue(apqn);
> > +ÂÂÂÂÂÂÂ if (!q) {
> > +ÂÂÂÂÂÂÂÂÂÂÂ ret = -EADDRNOTAVAIL;
> > +ÂÂÂÂÂÂÂÂÂÂÂ goto rewind;
> > +ÂÂÂÂÂÂÂ }
> > +ÂÂÂÂÂÂÂ if (q->matrix_mdev) {
>
> If somebody assigns the same domain a second time, the assignment will
> fail because the matrix_mdev will already have been associated with the
> queue. I don't think it is appropriate to fail the assignment if the

It is usual to report a failure in the case the operation requested has 
already be done.
But we can do as you want. Any other opinion?

> q->matrix_mdev is the same as the input matrix_mdev. This should be
> changed to:
>
>  ÂÂÂÂif (q->matrix_mdev != matrix_mdev)

You surely want to say: add this, not change to this. ;)

>

Thanks for commenting,

Regards,
Pierre


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