Re: [PATCH V5 7/9] virtio: allow to unbreak virtqueue

[Jason Wang]

On Wed, May 18, 2022 at 6:04 PM Cornelia Huck <cohuck@xxxxxxxxxx> wrote:
>
> On Wed, May 18 2022, Jason Wang <jasowang@xxxxxxxxxx> wrote:
>
> > This patch allows the new introduced __virtio_break_device() to
> > unbreak the virtqueue.
> >
> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> > Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
> > Cc: Marc Zyngier <maz@xxxxxxxxxx>
> > Cc: Halil Pasic <pasic@xxxxxxxxxxxxx>
> > Cc: Cornelia Huck <cohuck@xxxxxxxxxx>
> > Cc: Vineeth Vijayan <vneethv@xxxxxxxxxxxxx>
> > Cc: Peter Oberparleiter <oberpar@xxxxxxxxxxxxx>
> > Cc: linux-s390@xxxxxxxxxxxxxxx
> > Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> > ---
> >  drivers/virtio/virtio_ring.c | 21 +++++++++++++++++++++
> >  include/linux/virtio.h       |  1 +
> >  2 files changed, 22 insertions(+)
> >
> > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> > index cfb028ca238e..5b7df7c455f0 100644
> > --- a/drivers/virtio/virtio_ring.c
> > +++ b/drivers/virtio/virtio_ring.c
> > @@ -2397,6 +2397,27 @@ void virtio_break_device(struct virtio_device *dev)
> >  }
> >  EXPORT_SYMBOL_GPL(virtio_break_device);
> >
> > +/*
> > + * This should allow the device to be used by the driver. You may
> > + * need to grab appropriate locks to flush. This should only be used
>
> Hm, to flush what?

How about "to flush the write to vq->broken"?

>
> > + * in some specific case e.g (probing and restoring). Driver should
> > + * not call this directly.
>
> Maybe "This function should only be called by the core, not directly by
> the driver."?

Ok.

Thanks

>
> > + */
> > +void __virtio_unbreak_device(struct virtio_device *dev)
> > +{
> > +     struct virtqueue *_vq;
> > +
> > +     spin_lock(&dev->vqs_list_lock);
> > +     list_for_each_entry(_vq, &dev->vqs, list) {
> > +             struct vring_virtqueue *vq = to_vvq(_vq);
> > +
> > +             /* Pairs with READ_ONCE() in virtqueue_is_broken(). */
> > +             WRITE_ONCE(vq->broken, false);
> > +     }
> > +     spin_unlock(&dev->vqs_list_lock);
> > +}
> > +EXPORT_SYMBOL_GPL(__virtio_unbreak_device);
> > +
> >  dma_addr_t virtqueue_get_desc_addr(struct virtqueue *_vq)
> >  {
> >       struct vring_virtqueue *vq = to_vvq(_vq);
>