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Date:   Thu, 21 Jul 2022 17:15:34 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
        virtualization@...ts.linux-foundation.org
Cc:     Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Johannes Berg <johannes@...solutions.net>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <markgross@...nel.org>,
        Vadim Pasternak <vadimp@...dia.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Cornelia Huck <cohuck@...hat.com>,
        Halil Pasic <pasic@...ux.ibm.com>,
        Eric Farman <farman@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Vincent Whitchurch <vincent.whitchurch@...s.com>,
        linux-um@...ts.infradead.org, netdev@...r.kernel.org,
        platform-driver-x86@...r.kernel.org,
        linux-remoteproc@...r.kernel.org, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org, bpf@...r.kernel.org,
        kangjie.xu@...ux.alibaba.com
Subject: Re: [PATCH v12 22/40] virtio_ring: introduce virtqueue_resize()


在 2022/7/20 11:04, Xuan Zhuo 写道:
> 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@...ux.alibaba.com>


Acked-by: Jason Wang <jasowang@...hat.com>


> ---
>   drivers/virtio/virtio_ring.c | 69 ++++++++++++++++++++++++++++++++++++
>   include/linux/virtio.h       |  3 ++
>   2 files changed, 72 insertions(+)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index b092914e9dcd..cf4379175163 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -2545,6 +2545,75 @@ 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 callback 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.
> + * 0: success.
> + * -ENOMEM: Failed to allocate a new ring, fall back to the original ring size.
> + *  vq can still work normally
> + * -EBUSY: Failed to sync with device, vq may not work properly
> + * -ENOENT: Transport or device not supported
> + * -E2BIG/-EINVAL: num error
> + * -EPERM: Operation not permitted
> + *
> + */
> +int virtqueue_resize(struct virtqueue *_vq, u32 num,
> +		     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 (num > vq->vq.num_max)
> +		return -E2BIG;
> +
> +	if (!num)
> +		return -EINVAL;
> +
> +	if ((vq->packed_ring ? vq->packed.vring.num : vq->split.vring.num) == num)
> +		return 0;
> +
> +	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)
> +		err = virtqueue_resize_packed(_vq, num);
> +	else
> +		err = virtqueue_resize_split(_vq, num);
> +
> +	if (vdev->config->enable_vq_after_reset(_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 129bde7521e3..62e31bca5602 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

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