Virtualization - Apr 2021 - [PATCH v6 09/10] vduse: Introduce VDUSE - vDPA Device in Userspace

? 2021/4/12 ??4:02, Yongji Xie ??:
> On Mon, Apr 12, 2021 at 3:16 PM Jason Wang <jasowang at redhat.com>
wrote:
>>
>> ? 2021/4/9 ??4:02, Yongji Xie ??:
>>>>>>> +};
>>>>>>> +
>>>>>>> +struct vduse_dev_config_data {
>>>>>>> +     __u32 offset; /* offset from the beginning of
config space */
>>>>>>> +     __u32 len; /* the length to read/write */
>>>>>>> +     __u8 data[VDUSE_CONFIG_DATA_LEN]; /* data
buffer used to read/write */
>>>>>> Note that since VDUSE_CONFIG_DATA_LEN is part of uAPI
it means we can
>>>>>> not change it in the future.
>>>>>>
>>>>>> So this might suffcient for future features or all type
of virtio devices.
>>>>>>
>>>>> Do you mean 256 is no enough here?
>>>> Yes.
>>>>
>>> But this request will be submitted multiple times if config lengh
is
>>> larger than 256. So do you think whether we need to extent the size
to
>>> 512 or larger?
>>
>> So I think you'd better either:
>>
>> 1) document the limitation (256) in somewhere, (better both uapi and
doc)
>>
> But the VDUSE_CONFIG_DATA_LEN doesn't mean the limitation of
> configuration space. It only means the maximum size of one data
> transfer for configuration space. Do you mean document this?

Yes, and another thing is that since you're using 
data[VDUSE_CONFIG_DATA_LEN] in the uapi, it implies the length is always 
256 which seems not good and not what the code is wrote.

Thanks

>
> Thanks,
> Yongji
>