Add option to skip cpu feature and model verification in libvirt and rely on qemu 'enforce' option

[John Levon]

On Wed, Nov 23, 2022 at 01:45:37PM +0000, Daniel P. Berrangé wrote:

> Indeed, the very fact that libvirt exists and is widely used, is what
> allows QEMU to deprecated and rename stuff on a pretty aggressive
> schedule. If libvirt wasn't providing this isolation, then it is
> unlikely QEMU would have adopted its 2 release deprecated cycle,
> and would be locked into their mistakes for a much longer period.

My understanding was that qemu no longer change existing CPU model definitions,
but instead introduce new versions (like IcelakeServer-V6), and that's how they
can make changes as needed. Or are they still arbitrarily changing/breaking
*existing* definitions in incompatible ways?

> IOW, libvirt is allowing QEMU to fix their own technical debt on a
> more aggressive timeframe, albeit at some cost to libvirt maintainers.

I'd be interested in one or two specific examples so I can understand this
properly.

thanks
john