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

Jason Wang
2022-04-12T02:49:40Z

On Tue, Apr 12, 2022 at 10:47 AM Jason Wang <jasowang@redhat.com> wrote:
>
>
> 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

For [1] I meant
https://lore.kernel.org/lkml/20220406083538.16274-1-jasowang@redhat.com/

Thanks

> 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. */