netdev - Re: [PATCH v9 11/32] virtio_ring: split: introduce virtqueue_resize

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Date:   Tue, 12 Apr 2022 13:53:44 +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 11/32] virtio_ring: split: introduce
 virtqueue_resize_split()


在 2022/4/6 上午11:43, Xuan Zhuo 写道:
> virtio ring split supports resize.
>
> Only after the new vring is successfully allocated based on the new num,
> we will release the old vring. In any case, an error is returned,
> indicating that the vring still points to the old vring.
>
> In the case of an error, the caller must
> re-initialize(virtqueue_reinit_split()) the virtqueue to ensure that the
> vring can be used.
>
> In addition, vring_align, may_reduce_num are necessary for reallocating
> vring, so they are retained for creating vq.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> ---
>   drivers/virtio/virtio_ring.c | 47 ++++++++++++++++++++++++++++++++++++
>   1 file changed, 47 insertions(+)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 3dc6ace2ba7a..33864134a744 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -139,6 +139,12 @@ struct vring_virtqueue {
>   			/* DMA address and size information */
>   			dma_addr_t queue_dma_addr;
>   			size_t queue_size_in_bytes;
> +
> +			/* The parameters for creating vrings are reserved for
> +			 * creating new vring.
> +			 */
> +			u32 vring_align;
> +			bool may_reduce_num;
>   		} split;
>   
>   		/* Available for packed ring */
> @@ -199,6 +205,7 @@ struct vring_virtqueue {
>   };
>   
>   static struct vring_desc_extra *vring_alloc_desc_extra(unsigned int num);
> +static void vring_free(struct virtqueue *_vq);
>   
>   /*
>    * Helpers.
> @@ -1088,6 +1095,8 @@ static struct virtqueue *vring_create_virtqueue_split(
>   		return NULL;
>   	}
>   
> +	to_vvq(vq)->split.vring_align = vring_align;
> +	to_vvq(vq)->split.may_reduce_num = may_reduce_num;


It looks to me the above should belong to patch 6.


>   	to_vvq(vq)->split.queue_dma_addr = dma_addr;
>   	to_vvq(vq)->split.queue_size_in_bytes = queue_size_in_bytes;
>   	to_vvq(vq)->we_own_ring = true;
> @@ -1095,6 +1104,44 @@ static struct virtqueue *vring_create_virtqueue_split(
>   	return vq;
>   }
>   
> +static int virtqueue_resize_split(struct virtqueue *_vq, u32 num)
> +{
> +	struct vring_virtqueue *vq = to_vvq(_vq);
> +	struct virtio_device *vdev = _vq->vdev;
> +	struct vring_desc_state_split *state;
> +	struct vring_desc_extra *extra;
> +	size_t queue_size_in_bytes;
> +	dma_addr_t dma_addr;
> +	struct vring vring;
> +	int err = -ENOMEM;
> +	void *queue;
> +
> +	queue = vring_alloc_queue_split(vdev, &dma_addr, &num,
> +					vq->split.vring_align,
> +					vq->weak_barriers,
> +					vq->split.may_reduce_num);
> +	if (!queue)
> +		return -ENOMEM;
> +
> +	queue_size_in_bytes = vring_size(num, vq->split.vring_align);
> +
> +	err = vring_alloc_state_extra_split(num, &state, &extra);
> +	if (err) {
> +		vring_free_queue(vdev, queue_size_in_bytes, queue, dma_addr);
> +		return -ENOMEM;
> +	}
> +
> +	vring_free(&vq->vq);
> +
> +	vring_init(&vring, num, queue, vq->split.vring_align);
> +	vring_virtqueue_attach_split(vq, vring, state, extra);
> +	vq->split.queue_dma_addr = dma_addr;
> +	vq->split.queue_size_in_bytes = queue_size_in_bytes;


I wonder if it's better to move the above assignments to 
vring_virtqueue_attach_split().

Other looks good.

Thanks


> +
> +	vring_virtqueue_init_split(vq, vdev, true);
> +	return 0;
> +}
> +
>   
>   /*
>    * Packed ring specific functions - *_packed().