Re: [PATCH v9 02/32] virtio: struct virtio_config_ops add callbacks for queue_reset

Jason Wang
2022-04-12T02:48:03Z

在 2022/4/6 上午11:43, Xuan Zhuo 写道:
> Performing reset on a queue is divided into four steps:
>
> 1. transport: notify the device to reset the queue
> 2. vring: recycle the buffer submitted
> 3. vring: reset/resize the vring (may re-alloc)
> 4. transport: mmap vring to device, and enable the queue

Nit: it looks to me we'd better say it's an example (since step 3 or
even 2 is not a must).

>
> In order to support queue reset, add two callbacks(reset_vq,
> enable_reset_vq) in struct virtio_config_ops to implement steps 1 and 4.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> ---
> include/linux/virtio_config.h | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
> index 4d107ad31149..d4adcd0e1c57 100644
> --- a/include/linux/virtio_config.h
> +++ b/include/linux/virtio_config.h
> @@ -74,6 +74,16 @@ struct virtio_shm_region {
> * @set_vq_affinity: set the affinity for a virtqueue (optional).
> * @get_vq_affinity: get the affinity for a virtqueue (optional).
> * @get_shm_region: get a shared memory region based on the index.
> + * @reset_vq: reset a queue individually (optional).
> + * vq: the virtqueue
> + * Returns 0 on success or error status
> + * reset_vq will guarantee that the callbacks are disabled and synchronized.
> + * Except for the callback, the caller should guarantee that the vring is

I wonder what's the implications for virtio hardening[1]. In that
series, we agree to have a synchronize_vqs() config ops to make sure
callbacks are synchronized.

It uses a global flag and a device wise synchronization mechanism. It
looks to me we need to switch to

1) per virtqueue flag
2) per virtqueue synchronization

Thanks

> + * not accessed by any functions of virtqueue.
> + * @enable_reset_vq: enable a reset queue
> + * vq: the virtqueue
> + * Returns 0 on success or error status
> + * If reset_vq is set, then enable_reset_vq must also be set.
> */
> typedef void vq_callback_t(struct virtqueue *);
> struct virtio_config_ops {
> @@ -100,6 +110,8 @@ struct virtio_config_ops {
> int index);
> bool (*get_shm_region)(struct virtio_device *vdev,
> struct virtio_shm_region *region, u8 id);
> + int (*reset_vq)(struct virtqueue *vq);
> + int (*enable_reset_vq)(struct virtqueue *vq);
> };
>
> /* If driver didn't advertise the feature, it will never appear. */