Re: [Qemu-devel] [PATCH v4 09/11] virtio-net: update the head descriptor in a chain lastly

[Jason Wang <jasowang@redhat.com>]

On 2019/2/20 下午12:01, Wei Xu wrote:
>>
>>> AFAICT, virtqueue_fill() is a generic API for all relevant userspace virtio
>>> devices that do not support batching , without touching virtqueue_fill(),
>>> supporting batching changes the meaning of the parameter 'idx' which should
>>> be kept overall.
>>>
>>> To fix it, I got two proposals so far:
>>> 1). batching support(two APIs needed to keep compatibility)
>>> 2). save a head elem for a vq instead of caching an array of elems like vhost,
>>>      and introduce a new API(virtqueue_chain_fill()) functioning with an
>>>      additional parameter 'more' to the current virtqueue_fill() to indicate if
>>>      there are more descriptor(s) coming in a chain.
>>>
>>> Either way it changes the API somehow and it does not seem to be clean and clear
>>> as wanted.
>> It's as simple as accepting an array of elems in e.g
>> virtqueue_fill_batched()?
> It is trivial for both, my concern is an array elements need to be allocated dynamically
> due to vq size which no any other devices are using, a head would be enough for 2.
>

Do you see any issue for this?

Thanks