Re: [Qemu-devel] [Qemu-ppc] [PATCHv3 0/4] Clean up compatibility mode handling

[Andrea Bolognani]

On Fri, 2017-05-12 at 17:33 +1000, David Gibson wrote:
> > The goal of this series is indeed to switch from raw to architected but I
> > agree that it shouldn't affect existing machine types. This probably calls
> > for some compat prop.
> 
> So, I have mixed feelings about this.
> 
> 1. Yes, the series was intended to switch from preferring raw to
> preferring architected mode.
> 
> 2. No, it shouldn't have affected older machine types - I didn't think
> that through.
> 
> But, having made the mistake, I'm not sure it's worth correcting.  I
> don't actually expect this to break guests, and fixing it now that
> it's already there will be messy, and raises the possibility of new
> behavioural change between older and newer subversions of 2.9.

I'm not sure how QEMU handles maintenance branches, but it
seems to me that it would be better to confine this issue
to a single buggy release rather than carrying it forward
forever.

Downstream releases can just backport the relevant commits
and pretend nothing ever happened :)

-- 
Andrea Bolognani / Red Hat / Virtualization