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

[Jason Wang <jasowang@xxxxxxxxxx>]

在 2022/7/1 16:45, Xuan Zhuo 写道:
> On Fri, 1 Jul 2022 16:26:25 +0800, Jason Wang <jasowang@xxxxxxxxxx> 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@xxxxxxxxxxxxxxxxx>
> > > ---
> > >    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;