netdev - Re: [PATCH 06/33] virtio_ring: introduce virtqueue

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Date:   Fri, 3 Feb 2023 04:05:38 -0500
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Björn Töpel <bjorn@...nel.org>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Menglong Dong <imagedong@...cent.com>,
        Kuniyuki Iwashima <kuniyu@...zon.com>,
        Petr Machata <petrm@...dia.com>,
        virtualization@...ts.linux-foundation.org, bpf@...r.kernel.org
Subject: Re: [PATCH 06/33] virtio_ring: introduce virtqueue_reset()

On Thu, Feb 02, 2023 at 07:00:31PM +0800, Xuan Zhuo wrote:
> Introduce virtqueue_reset() to release all buffer inside vq.
> 
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> ---
>  drivers/virtio/virtio_ring.c | 50 ++++++++++++++++++++++++++++++++++++
>  include/linux/virtio.h       |  2 ++
>  2 files changed, 52 insertions(+)
> 
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index e32046fd15a5..7dfce7001f9f 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -2735,6 +2735,56 @@ int virtqueue_resize(struct virtqueue *_vq, u32 num,
>  }
>  EXPORT_SYMBOL_GPL(virtqueue_resize);
>  
> +/**
> + * virtqueue_reset - reset the vring of vq

..., detach and recycle all unused buffers

	after all this is why we are doing this reset, right?

> + * @_vq: the struct virtqueue we're talking about.
> + * @recycle: callback for recycle the useless buffer

not useless :) unused:

	callback to recycle unused buffers

I know we have the same confusion in virtqueue_resize, I will fix
that.

> + *
> + * 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.
> + * 0: success.
> + * -EBUSY: Failed to sync with device, vq may not work properly
> + * -ENOENT: Transport or device not supported
> + * -EPERM: Operation not permitted
> + */
> +int virtqueue_reset(struct virtqueue *_vq,
> +		    void (*recycle)(struct virtqueue *vq, void *buf))
> +{
> +	struct vring_virtqueue *vq = to_vvq(_vq);
> +	struct virtio_device *vdev = vq->vq.vdev;
> +	void *buf;
> +	int err;
> +
> +	if (!vq->we_own_ring)
> +		return -EPERM;
> +
> +	if (!vdev->config->disable_vq_and_reset)
> +		return -ENOENT;
> +
> +	if (!vdev->config->enable_vq_after_reset)
> +		return -ENOENT;
> +
> +	err = vdev->config->disable_vq_and_reset(_vq);
> +	if (err)
> +		return err;
> +
> +	while ((buf = virtqueue_detach_unused_buf(_vq)) != NULL)
> +		recycle(_vq, buf);
> +
> +	if (vq->packed_ring)
> +		virtqueue_reinit_packed(vq);
> +	else
> +		virtqueue_reinit_split(vq);
> +
> +	if (vdev->config->enable_vq_after_reset(_vq))
> +		return -EBUSY;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(virtqueue_reset);
> +
>  /* 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 3ebb346ebb7c..3ca2edb1aef3 100644
> --- a/include/linux/virtio.h
> +++ b/include/linux/virtio.h
> @@ -105,6 +105,8 @@ 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));
> +int virtqueue_reset(struct virtqueue *vq,
> +		    void (*recycle)(struct virtqueue *vq, void *buf));
>  
>  /**
>   * struct virtio_device - representation of a device using virtio
> -- 
> 2.32.0.3.g01195cf9f