Re: [Qemu-devel] address order of virtio-mmio devices

[Peter Maydell]

On 30 January 2015 at 09:54, Daniel P. Berrange <address@hidden> wrote:
> While it is clear there is no solution that works correctly with all
> kernels, I hate to think that we're going to stick with an ordering
> that is clearly wrong for modern kernels, forever going forward. The
> aarch64 world is only just starting out, so on balance I think we
> should optimize for the future rather than the past, since that gives
> right behaviour for orders of magnitude more people in the long term.

Yeah, I agree it's awkward. But I hate breaking people's
working setups, and we have no guarantee the kernel won't
change again in the future.

You could try asking the kernel folk to revert that patch on
the basis that it breaks things...

> Also can we start using a versioned machine type for ARM, and make the
> new machine type have the correct ordering for current kernels.

No, not yet. We are miles and miles and miles away from being
able to do cross-version migration correctly, and adding version
machine types is accepting a huge maintenance burden from now
extending indefinitely into the future. (It only works for x86,
as I understand it, because RedHat do a lot of testing of various
migration scenarios including cross-version, and even then we miss
things. Nobody has as yet suggested they're doing or even planning
to do that level of testing on the ARM boards. I'm not going to
add versioned boards until it becomes absolutely required. Having
working within-version migration would be a start.

-- PMM