Re: [Qemu-devel] [PATCH] arm: define version-based machine type for ARM

[Peter Maydell]

On 15 January 2015 at 18:52, Wei Huang <address@hidden> wrote:
> On 01/15/2015 12:10 PM, Peter Maydell wrote:
>> I don't think we're anywhere ready yet to support between
>> version migration compatibility. We will want this *eventually*
>> but we are a long long way away from needing it...(maybe a
>> year?)
> Thanks, Peter. I think migration support is getting closer than one
> year. It might not create problems at the beginning. So I understand
> your point.

Well, at the moment in mainline migration doesn't work at all!
So we need to spend a period of time stabilising it, and
making sure that the 'virt' machine has all the capabilities
we need and that we've made any further breaking changes which
we need to do. Then we need to have somebody who's willing
to do the extensive between-version migration testing that
you need in order for the feature to actually work in practice.
It's only when we are sure that we can actually support
cross-version migration and we have the necessary demand
from users (ie: distros, I think), that we should start
creating per-version machines and backwards-compatibility
property settings and so on.

thanks
-- PMM