On Mon, Mar 14, 2022 at 05:34:55PM +0800, Xuan Zhuo wrote:
> Introduce virtqueue_resize() to implement the resize of vring.
> Based on these, the driver can dynamically adjust the size of the vring.
> For example: ethtool -G.
>
> virtqueue_resize() implements resize based on the vq reset function. In
> case of failure to allocate a new vring, it will give up resize and use
> the original vring.
>
> During this process, if the re-enable reset vq fails, the vq can no
> longer be used. Although the probability of this situation is not high.
>
> The parameter recycle is used to recycle the buffer that is no longer
> used.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
> ---
> drivers/virtio/virtio_ring.c | 67 ++++++++++++++++++++++++++++++++++++
> include/linux/virtio.h | 3 ++
> 2 files changed, 70 insertions(+)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index fb0abf9a2f57..b1dde086a8a4 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -2528,6 +2528,73 @@ struct virtqueue *vring_create_virtqueue(
> }
> EXPORT_SYMBOL_GPL(vring_create_virtqueue);
>
> +/**
> + * virtqueue_resize - resize the vring of vq
> + * @vq: the struct virtqueue we're talking about.
> + * @num: new ring num
> + * @recycle: callback for recycle the useless buffer
> + *
> + * When it is really necessary to create a new vring, it will set the current vq
> + * into the reset state. Then call the passed cb to recycle the buffer that is
> + * no longer used. Only after the new vring is successfully created, the old
> + * vring will be released.
> + *
> + * Caller must ensure we don't call this with other virtqueue operations
> + * at the same time (except where noted).
> + *
> + * Returns zero or a negative error.
> + * -ENOMEM: create new vring fail. But vq can still work
> + * -EBUSY: reset/re-enable vq fail. vq may cannot work
> + * -ENOENT: not support resize
> + * -E2BIG/-EINVAL: param num error
> + */
> +int virtqueue_resize(struct virtqueue *vq, u32 num,
> + void (*recycle)(struct virtqueue *vq, void *buf))
> +{
> + struct virtio_device *vdev = vq->vdev;
> + void *buf;
> + int err;
> +
> + if (num > vq->num_max)
> + return -E2BIG;
> +
> + if (!num)
> + return -EINVAL;
> +
> + if (to_vvq(vq)->packed.vring.num == num)
> + return 0;
> +
> + if (!vq->vdev->config->reset_vq)
> + return -ENOENT;
> +
> + if (!vq->vdev->config->enable_reset_vq)
> + return -ENOENT;
> +
> + err = vq->vdev->config->reset_vq(vq);
> + if (err) {
> + if (err != -ENOENT)
> + err = -EBUSY;
> + return err;
> + }
> +
> + while ((buf = virtqueue_detach_unused_buf(vq)) != NULL)
> + recycle(vq, buf);
So all this callback can do now is drop all buffers, and I think that is
not great. Can we store them and invoke the callback after queue is
enabled?
> +
> + if (virtio_has_feature(vdev, VIRTIO_F_RING_PACKED))
> + err = virtqueue_resize_packed(vq, num);
> + else
> + err = virtqueue_resize_split(vq, num);
> +
> + if (err)
> + err = -ENOMEM;
> +
> + if (vq->vdev->config->enable_reset_vq(vq))
> + return -EBUSY;
> +
> + return err;
> +}
> +EXPORT_SYMBOL_GPL(virtqueue_resize);
> +
> /* Only available for split ring */
> struct virtqueue *vring_new_virtqueue(unsigned int index,
> unsigned int num,
> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> index d59adc4be068..c86ff02e0ca0 100644
> --- a/include/linux/virtio.h
> +++ b/include/linux/virtio.h
> @@ -91,6 +91,9 @@ dma_addr_t virtqueue_get_desc_addr(struct virtqueue *vq);
> dma_addr_t virtqueue_get_avail_addr(struct virtqueue *vq);
> dma_addr_t virtqueue_get_used_addr(struct virtqueue *vq);
>
> +int virtqueue_resize(struct virtqueue *vq, u32 num,
> + void (*recycle)(struct virtqueue *vq, void *buf));
> +
> /**
> * virtio_device - representation of a device using virtio
> * @index: unique position on the virtio bus
> --
> 2.31.0
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