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Date: Tue, 12 Apr 2022 14:41:18 +0800
From: Jason Wang <jasowang@...hat.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
virtualization@...ts.linux-foundation.org
Cc: Jeff Dike <jdike@...toit.com>, Richard Weinberger <richard@....at>,
Anton Ivanov <anton.ivanov@...bridgegreys.com>,
"Michael S. Tsirkin" <mst@...hat.com>,
"David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
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>,
Heiko Carstens <hca@...ux.ibm.com>,
Vasily Gorbik <gor@...ux.ibm.com>,
Christian Borntraeger <borntraeger@...ux.ibm.com>,
Alexander Gordeev <agordeev@...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>,
Johannes Berg <johannes.berg@...el.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
Subject: Re: [PATCH v9 18/32] virtio_ring: introduce virtqueue_resize()
在 2022/4/6 上午11:43, 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>
> ---
> 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 06f66b15c86c..6250e19fc5bf 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -2554,6 +2554,75 @@ 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.
Should we document that the virtqueue is kept unchanged (still
available) on (specific) failure?
> + */
> +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;
> + bool packed;
> + void *buf;
> + int err;
> +
> + if (!vq->we_own_ring)
> + return -EINVAL;
> +
> + if (num > vq->vq.num_max)
> + return -E2BIG;
> +
> + if (!num)
> + return -EINVAL;
> +
> + packed = virtio_has_feature(vdev, VIRTIO_F_RING_PACKED) ? true : false;
> +
> + if ((packed ? vq->packed.vring.num : vq->split.vring.num) == num)
> + return 0;
> +
> + if (!vdev->config->reset_vq)
> + return -ENOENT;
> +
> + if (!vdev->config->enable_reset_vq)
> + return -ENOENT;
> +
> + err = vdev->config->reset_vq(_vq);
> + if (err)
> + return err;
> +
> + while ((buf = virtqueue_detach_unused_buf(_vq)) != NULL)
> + recycle(_vq, buf);
> +
> + if (packed) {
> + err = virtqueue_resize_packed(_vq, num);
> + if (err)
> + virtqueue_reinit_packed(vq);
Calling reinit here seems a little bit odd, it looks more like a reset
of the virtqueue. Consider we may re-use virtqueue reset for more
purpose, I wonder if we need a helper like:
virtqueue_resize() {
vdev->config->reset_vq(_vq);
if (packed)
virtqueue_reinit_packed(_vq)
else
virtqueue_reinit_split(_vq)
}
Thanks
> + } else {
> + err = virtqueue_resize_split(_vq, num);
> + if (err)
> + virtqueue_reinit_split(vq);
> + }
> +
> + if (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
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