Re: [PATCH-for-9.1 v2 2/3] migration: Remove RDMA protocol handling

[Yu Zhang]

Hello Peter und Zhjian,

Thank you so much for letting me know about this. I'm also a bit surprised at
the plan for deprecating the RDMA migration subsystem.

> IMHO it's more important to know whether there are still users and whether
> they would still like to see it around.

> I admit RDMA migration was lack of testing(unit/CI test), which led to the a 
> few
> obvious bugs being noticed too late.

Yes, we are a user of this subsystem. I was unaware of the lack of test coverage
for this part. As soon as 8.2 was released, I saw that many of the
migration test
cases failed and came to realize that there might be a bug between 8.1
and 8.2, but
was unable to confirm and report it quickly to you.

The maintenance of this part could be too costly or difficult from
your point of view.

My concern is, this plan will forces a few QEMU users (not sure how
many) like us
either to stick to the RDMA migration by using an increasingly older
version of QEMU,
or to abandon the currently used RDMA migration.

Best regards,
Yu Zhang

On Mon, Apr 1, 2024 at 9:56 AM Zhijian Li (Fujitsu)
<lizhijian@fujitsu.com> wrote:
>
> Phil,
>
> on 3/29/2024 6:28 PM, Philippe Mathieu-Daudé wrote:
> >>
> >>
> >>> IMHO it's more important to know whether there are still users and
> >>> whether
> >>> they would still like to see it around.
> >>
> >> Agree.
> >> I didn't immediately express my opinion in V1 because I'm also
> >> consulting our
> >> customers for this feature in the future.
> >>
> >> Personally, I agree with Perter's idea that "I'd slightly prefer
> >> postponing it one
> >> more release which might help a bit of our downstream maintenance"
> >
> > Do you mind posting a deprecation patch to clarify the situation?
> >
>
> No problem, i just posted a deprecation patch, please take a look.
> https://lore.kernel.org/qemu-devel/20240401035947.3310834-1-lizhijian@fujitsu.com/T/#u
>
> Thanks
> Zhijian