Re: [PATCH RFC v2] vfio: Documentation for the migration region

Cornelia Huck
2021-12-07T11:16:43Z

On Mon, Dec 06 2021, Jason Gunthorpe <jgg@nvidia.com> wrote:

> On Mon, Dec 06, 2021 at 07:06:35PM +0100, Cornelia Huck wrote:
>
>> We're discussing a complex topic here, and we really don't want to
>> perpetuate an unclear uAPI. This is where my push for more precise
>> statements is coming from.
>
> I appreciate that, and I think we've made a big effort toward that
> direction.
>
> Can we have some crisp feedback which statements need SHOULD/MUST/MUST
> NOT and come to something?

I'm not sure what I should actually comment on, some general remarks:

- If we consider a possible vfio-ccw implementation that will quiesce
the device and not rely on tracking I/O, we need to make the parts
that talk about tracking non-mandatory.
- NDMA sounds like something that needs to be non-mandatory as well.
- The discussion regarding bit group changes has me confused. You seem
to be saying that mlx5 needs that, so it needs to have some mandatory
component; but are actually all devices able to deal with those bits
changing as a group?
- In particular, the flow needs definitive markings about what is
mandatory to implement, what is strongly suggested, and what is
optional. It is unclear to me what is really expected, and what is
simply one way to implement it.

>
> The world needs to move forward, we can't debate this endlessly
> forever. It is already another 6 weeks past since the last mlx5 driver
> posting.

6 weeks is already blazingly fast in any vfio migration discussion. /s

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