[PATCH v11 25/40] virtio: allow to unbreak/break virtqueue individually

[Michael S. Tsirkin]

On Wed, Jun 29, 2022 at 02:56:41PM +0800, Xuan Zhuo wrote:
> This patch allows the new introduced
> __virtqueue_break()/__virtqueue_unbreak() to break/unbreak the
> virtqueue.
> 
> Signed-off-by: Xuan Zhuo <xuanzhuo at linux.alibaba.com>

I wonder how this interacts with the hardening patches.
Jason?

> ---
>  drivers/virtio/virtio_ring.c | 24 ++++++++++++++++++++++++
>  include/linux/virtio.h       |  3 +++
>  2 files changed, 27 insertions(+)
> 
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 5ec43607cc15..7b02be7fce67 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -2744,6 +2744,30 @@ unsigned int virtqueue_get_vring_size(struct virtqueue *_vq)
>  }
>  EXPORT_SYMBOL_GPL(virtqueue_get_vring_size);
>  
> +/*
> + * This function should only be called by the core, not directly by the driver.
> + */
> +void __virtqueue_break(struct virtqueue *_vq)
> +{
> +	struct vring_virtqueue *vq = to_vvq(_vq);
> +
> +	/* Pairs with READ_ONCE() in virtqueue_is_broken(). */
> +	WRITE_ONCE(vq->broken, true);
> +}
> +EXPORT_SYMBOL_GPL(__virtqueue_break);
> +
> +/*
> + * This function should only be called by the core, not directly by the driver.
> + */
> +void __virtqueue_unbreak(struct virtqueue *_vq)
> +{
> +	struct vring_virtqueue *vq = to_vvq(_vq);
> +
> +	/* Pairs with READ_ONCE() in virtqueue_is_broken(). */
> +	WRITE_ONCE(vq->broken, false);
> +}

I don't think these "Pairs" comments have any value.


> +EXPORT_SYMBOL_GPL(__virtqueue_unbreak);
> +
>  bool virtqueue_is_broken(struct virtqueue *_vq)
>  {
>  	struct vring_virtqueue *vq = to_vvq(_vq);
> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> index 1272566adec6..dc474a0d48d1 100644
> --- a/include/linux/virtio.h
> +++ b/include/linux/virtio.h
> @@ -138,6 +138,9 @@ bool is_virtio_device(struct device *dev);
>  void virtio_break_device(struct virtio_device *dev);
>  void __virtio_unbreak_device(struct virtio_device *dev);
>  
> +void __virtqueue_break(struct virtqueue *_vq);
> +void __virtqueue_unbreak(struct virtqueue *_vq);
> +
>  void virtio_config_changed(struct virtio_device *dev);
>  #ifdef CONFIG_PM_SLEEP
>  int virtio_device_freeze(struct virtio_device *dev);
> -- 
> 2.31.0