Re: [PATCH v11 08/40] virtio_ring: split: extract the logic of alloc queue

[Jason Wang <jasowang@redhat.com>]

在 2022/7/1 16:45, Xuan Zhuo 写道:
> On Fri, 1 Jul 2022 16:26:25 +0800, Jason Wang <jasowang@redhat.com> wrote:
>> 在 2022/6/29 14:56, Xuan Zhuo 写道:
>>> Separate the logic of split to create vring queue.
>>>
>>> This feature is required for subsequent virtuqueue reset vring.
>>>
>>> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
>>> ---
>>>    drivers/virtio/virtio_ring.c | 68 ++++++++++++++++++++++--------------
>>>    1 file changed, 42 insertions(+), 26 deletions(-)
>>>
>>> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
>>> index 49d61e412dc6..a9ceb9c16c54 100644
>>> --- a/drivers/virtio/virtio_ring.c
>>> +++ b/drivers/virtio/virtio_ring.c
>>> @@ -949,28 +949,19 @@ static void vring_free_split(struct vring_virtqueue_split *vring,
>>>    	kfree(vring->desc_extra);
>>>    }
>>>
>>> -static struct virtqueue *vring_create_virtqueue_split(
>>> -	unsigned int index,
>>> -	unsigned int num,
>>> -	unsigned int vring_align,
>>> -	struct virtio_device *vdev,
>>> -	bool weak_barriers,
>>> -	bool may_reduce_num,
>>> -	bool context,
>>> -	bool (*notify)(struct virtqueue *),
>>> -	void (*callback)(struct virtqueue *),
>>> -	const char *name)
>>> +static int vring_alloc_queue_split(struct vring_virtqueue_split *vring,
>>> +				   struct virtio_device *vdev,
>>> +				   u32 num,
>>> +				   unsigned int vring_align,
>>> +				   bool may_reduce_num)
>>>    {
>>> -	struct virtqueue *vq;
>>>    	void *queue = NULL;
>>>    	dma_addr_t dma_addr;
>>> -	size_t queue_size_in_bytes;
>>> -	struct vring vring;
>>>
>>>    	/* We assume num is a power of 2. */
>>>    	if (num & (num - 1)) {
>>>    		dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
>>> -		return NULL;
>>> +		return -EINVAL;
>>>    	}
>>>
>>>    	/* TODO: allocate each queue chunk individually */
>>> @@ -981,11 +972,11 @@ static struct virtqueue *vring_create_virtqueue_split(
>>>    		if (queue)
>>>    			break;
>>>    		if (!may_reduce_num)
>>> -			return NULL;
>>> +			return -ENOMEM;
>>>    	}
>>>
>>>    	if (!num)
>>> -		return NULL;
>>> +		return -ENOMEM;
>>>
>>>    	if (!queue) {
>>>    		/* Try to get a single page. You are my only hope! */
>>> @@ -993,21 +984,46 @@ static struct virtqueue *vring_create_virtqueue_split(
>>>    					  &dma_addr, GFP_KERNEL|__GFP_ZERO);
>>>    	}
>>>    	if (!queue)
>>> -		return NULL;
>>> +		return -ENOMEM;
>>> +
>>> +	vring_init(&vring->vring, num, queue, vring_align);
>>>
>>> -	queue_size_in_bytes = vring_size(num, vring_align);
>>> -	vring_init(&vring, num, queue, vring_align);
>>> +	vring->queue_dma_addr = dma_addr;
>>> +	vring->queue_size_in_bytes = vring_size(num, vring_align);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static struct virtqueue *vring_create_virtqueue_split(
>>> +	unsigned int index,
>>> +	unsigned int num,
>>> +	unsigned int vring_align,
>>> +	struct virtio_device *vdev,
>>> +	bool weak_barriers,
>>> +	bool may_reduce_num,
>>> +	bool context,
>>> +	bool (*notify)(struct virtqueue *),
>>> +	void (*callback)(struct virtqueue *),
>>> +	const char *name)
>>> +{
>>> +	struct vring_virtqueue_split vring = {};
>>> +	struct virtqueue *vq;
>>> +	int err;
>>> +
>>> +	err = vring_alloc_queue_split(&vring, vdev, num, vring_align,
>>> +				      may_reduce_num);
>>> +	if (err)
>>> +		return NULL;
>>>
>>> -	vq = __vring_new_virtqueue(index, vring, vdev, weak_barriers, context,
>>> -				   notify, callback, name);
>>> +	vq = __vring_new_virtqueue(index, vring.vring, vdev, weak_barriers,
>>> +				   context, notify, callback, name);
>>>    	if (!vq) {
>>> -		vring_free_queue(vdev, queue_size_in_bytes, queue,
>>> -				 dma_addr);
>>> +		vring_free_split(&vring, vdev);
>>>    		return NULL;
>>>    	}
>>>
>>> -	to_vvq(vq)->split.queue_dma_addr = dma_addr;
>>> -	to_vvq(vq)->split.queue_size_in_bytes = queue_size_in_bytes;
>>> +	to_vvq(vq)->split.queue_dma_addr = vring.queue_dma_addr;
>>
>> Nit: having two queue_dma_addr seems redundant (so did queue_size_in_bytes).
> two?
>
> Where is the problem I don't understand?
>
> Thanks.


I meant we had:

         vring.vring = _vring;

in __vring_new_virtqueue().

This means we'd better initialize vring fully before that?

E.g

vring.queue_dma_addr = dma_addr;

...

__vring_new_virtqueue()

Thanks


>
>> Thanks
>>
>>
>>> +	to_vvq(vq)->split.queue_size_in_bytes = vring.queue_size_in_bytes;
>>>    	to_vvq(vq)->we_own_ring = true;
>>>
>>>    	return vq;