Re: [Qemu-devel] [RFC v2 0/4] adding mdev bus and vfio support

[Jike Song]

On 09/07/2016 11:38 AM, Neo Jia wrote:
> On Wed, Sep 07, 2016 at 10:22:26AM +0800, Jike Song wrote:
>> On 09/02/2016 11:03 PM, Alex Williamson wrote:
>>> On Fri,  2 Sep 2016 16:16:08 +0800
>>> Jike Song <address@hidden> wrote:
>>>
>>>> This patchset is based on NVidia's "Add Mediated device support" series, 
>>>> version 6:
>>>>
>>>>    http://www.spinics.net/lists/kvm/msg136472.html
>>>
>>>
>>> Hi Jike,
>>>
>>> I'm thrilled by your active participation here, but I'm confused which
>>> versions I should be reviewing and where the primary development is
>>> going.  Kirti sent v7 a week ago, so I would have expected a revision
>>> based on that rather than a re-write based on v6 plus incorporation of a
>>> few of Kirti's patches directly.
>>
>> Hi Alex,
>>
>> [Sorry! replied this on Monday but it was silently dropped by the our 
>> firewall]
>>
>>
>>
>> The v1 of this patchset was send as incremental ones, basing on Nvidia's v6, 
>> to
>> demonstrate how is it possible and beneficial to:
>>
>>      1, Introduce an independent device between physical and mdev;
>>      2, Simplify vfio-mdev and make it the most flexible for vendor drivers;
>>
>> Unfortunately neither was understood or adopted in v7:
>>
>>      http://www.spinics.net/lists/kvm/msg137081.html
>>
>> So here came the v2, as a standalone series, to give a whole and straight
>> demonstration. The reason of still basing on v6:
>>
>>      - Addressed all v6 comments (except the iommu part);
>>      - There is no comments yet for v7 (except the sysfs ones);
>>
>>
>>
>>> I liked the last version of these
>>> changes a lot, but we need to figure out how to combine development
>>> because we do not have infinite cycles for review available :-\  Thanks!
>>
>> Fully understand.
>>
>> Here is the dilemma: v6 is an obsolete version to work upon, v7 is still not
>> at the direction we prefer. 
> 
> Hi Jike,
> 
> I wish I could meet you in person in KVM forum couple weeks ago so we can 
> have a
> better discussion.

I wish I could have that opportunity, too!

> We are trying our best to accommodate almost all requirements / comments from 
> use cases and code reviews while keeping little (or none) architectural 
> changes
> between revisions.

Yes I saw that, there was little architectural change from v6 to v7,
that's what I will argue for :)

>> We would be highly glad and thankful if Neo/Kirti
>> would adopt the code in their next version, which will certainly form a
>> more simple and consolidated base for future co-development; otherwise
>> and we could at least discuss the concerns, in case of any.
>>
> 
> As I have said in my previous response to you, if you have any questions about
> adopting the framework that we have developed, you are very welcome to
> comment/speak out on the code review thread like others. And if it is 
> reasonable
> request and won't break other vendors' use case, we will adopt it (one example
> is the online file and removing the mdev pci dependency).
> 

Not limited to having questions about adoption, right? :)

We do think the framework itself had too much unnecessary logic and
imposed limitations to vendor drivers, also it's clearly possible to be
simplified.

> Just some update for you regarding the v7 patches, currently we are very
> actively trying to lock down the sysfs and management interfaces discussion.
> 
> So, if you would like to make the upstream happen sooner, please join us in 
> the
> v7 and following patch discussion instead of rewriting them.
> 

So as you said, I would comment on the v7 series to propose both architectural
and implementation changes, hoping this will help more.


--
Thanks,
Jike