Re: [PATCH V6 7/9] virtio: allow to unbreak virtqueue

[Xuan Zhuo <xuanzhuo@linux.alibaba.com>]

On Fri, 27 May 2022 14:01:18 +0800, Jason Wang <jasowang@redhat.com> wrote:
> This patch allows the new introduced __virtio_break_device() to
> unbreak the virtqueue.
>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: "Paul E. McKenney" <paulmck@kernel.org>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Halil Pasic <pasic@linux.ibm.com>
> Cc: Cornelia Huck <cohuck@redhat.com>
> Cc: Vineeth Vijayan <vneethv@linux.ibm.com>
> Cc: Peter Oberparleiter <oberpar@linux.ibm.com>
> Cc: linux-s390@vger.kernel.org
> Signed-off-by: Jason Wang <jasowang@redhat.com>

Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>

> ---
>  drivers/virtio/virtio_ring.c | 22 ++++++++++++++++++++++
>  include/linux/virtio.h       |  1 +
>  2 files changed, 23 insertions(+)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 9d0bae4293be..9c231e1fded7 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -2395,6 +2395,28 @@ 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 the write to
> + * vq->broken. This should only be used in some specific case e.g
> + * (probing and restoring). This function should only be called by the
> + * core, not directly by the driver.
> + */
> +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);
> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> index 5464f398912a..d8fdf170637c 100644
> --- a/include/linux/virtio.h
> +++ b/include/linux/virtio.h
> @@ -131,6 +131,7 @@ void unregister_virtio_device(struct virtio_device *dev);
>  bool is_virtio_device(struct device *dev);
>
>  void virtio_break_device(struct virtio_device *dev);
> +void __virtio_unbreak_device(struct virtio_device *dev);
>
>  void virtio_config_changed(struct virtio_device *dev);
>  #ifdef CONFIG_PM_SLEEP
> --
> 2.25.1
>