[dpdk-dev] [PATCH v1 1/2] vfio: make API return values consistent

[Burakov, Anatoly]

On 28-Oct-21 12:32 PM, Ferruh Yigit wrote:
> On 10/28/2021 12:11 PM, Xia, Chenbo wrote:
>>> -----Original Message-----
>>> From: Burakov, Anatoly <anatoly.burakov at intel.com>
>>> Sent: Thursday, October 28, 2021 6:30 PM
>>> To: Xia, Chenbo <chenbo.xia at intel.com>; dev at dpdk.org
>>> Subject: Re: [dpdk-dev] [PATCH v1 1/2] vfio: make API return values 
>>> consistent
>>>
>>> Hi Chenbo,
>>>
>>>> And do we need backport? As 'return -1' does not align with the API 
>>>> doxygen.
>>>>
>>>> Thanks,
>>>> Chenbo
>>>>
>>> Maybe it's the FreeBSD implementation that needs to be adjusted then,
>>> because none of those functions are valid on FreeBSD, and the
>>> documentation for VFIO functions explicitly mentions that on FreeBSD,
>>> they should return an error. I went with adjusting Linux implementation
>>> to minimize the amount of changes we have to make (and only change code
>>> path that no one uses in the first place), but maybe that was a wrong
>>> decision.
>>>
>>> I'm not sure if changing the API return value to match what was
>>> documented counts as an API change, so maybe backport to stable is not
>>> advised here.
>>
>> It's not a API change. My point is whether VFIO is present, users just 
>> use
>> the API to check if vfio support is there. In a kernel version that 
>> does not
>> support VFIO, he uses 'if(rte_vfio_is_enabled(XXX))' to check as the 
>> doxygen
>> says its return value should be 1 as true or 0 as false. He will get 
>> true (-1)
>> but VFIO is not there. That's why I think it's a bug and should be 
>> backported.
>>
>> But I think we can first discuss if we should drop the dummy 
>> implementation
>> as DPDK requires Linux kernel version >= 4.4 now so VFIO is always 
>> present.
>> I think it depends on by saying 'DPDK requires kernel version >= 4.4'. 
>> It's
>> a real _requirement_ or only a recommendation?
>>
>> Ferruh, David & Thomas, What do you think?
>>
> 
> My understanding is, it is a requirement. DPDK does not guarantee 
> support for
> kernels < 4.4.

I'll resubmit with some changes then. I'll drop the fallback entirely, 
and check FreeBSD implementations for bugginess, and maybe correct the 
doxygen comment where necessary.

-- 
Thanks,
Anatoly