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

[Pierre Morel]

On 28/03/2019 16:32, Tony Krowiak wrote:
> On 3/28/19 9:06 AM, Pierre Morel wrote:
> > 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

...
> > > > +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 /* Bits 41-47 
> > > must all be zeros */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.
>
> That is true, but if the queue is never used, there is nothing to reset.

:) OK


Regards,
Pierre

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