Re: [PATCH v2 18/25] hw/sd: ssi-sd: Bump up version ids of VMStateDescription

[Dr. David Alan Gilbert]

* Bin Meng (bmeng.cn@gmail.com) wrote:
> On Mon, Jan 25, 2021 at 12:59 AM Philippe Mathieu-Daudé <f4bug@amsat.org> 
> wrote:
> >
> > On 1/23/21 11:40 AM, Bin Meng wrote:
> > > From: Bin Meng <bin.meng@windriver.com>
> > >
> > > With all these fixes and improvements, there is no way for the
> > > VMStateDescription to keep backward compatibility. We will have
> > > to bump up version ids.
> >
> > Unfortunately this breaks bisectability (think about downstream
> > distributions cherry-picking patches individually).
> >
> > I don't think there is a problem increasing 2 -> 3 -> 4 -> 5
> > (Cc'ed David in case). Could you respin increasing the version
> > on each VMState change?
> >
> 
> I definitely could be wrong, the reason I posted a single patch to
> upreve the version is that, I was under an impression that in each big
> release (like here 5.2.0 -> 6.0.0), the incompatibility version id
> should be bumped up once.
> It does not look correct to me that in a big release we bump up the
> version id for 10 times.

I think I agree; I don't think we've ever done it incrementally like
that before.

It would only break bisectability if you were cross-version migrating
during the bisect which is rare.

> Since this is a series to fix issues in the ssi-sd, I don't think it's
> practical for downstream to just cherry-pick some commits while
> leaving some other commits there.

Never underestimate downstream :-)
However, please add a comment when you're doing incrimentals like this -
e.g. a TODO or something showing that it's unfinished and you need the
remaining patches so people don't do it accidentally.

Dave

> Regards,
> Bin
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK