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

[Ferruh Yigit]

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.