Re: [Qemu-devel] [PATCH 0/2] target-i386: "custom" CPU model + script to dump existing CPU models

[Paolo Bonzini]

On 24/06/2015 16:54, Peter Maydell wrote:
> > It's certainly okay for libvirt and OpenStack to use the host CPU
> > features in order to check whether a node will run a given VM.  However,
> > libvirt should trust that QEMU developers will not prevent a VM from
> > running on a previously viable host, just because you change the machine
> > type.
> 
> Note that this might be true for x86 but isn't (in full generality)
> necessarily so for other architectures like ARM. For instance if
> you have a host machine with a GICv3 with no v2-back-compatibility
> support, then you can run a VM whose machine type specifies a GICv3,
> but not machine types that require a GICv2...

Hmm, that was too terse.  Just because you change the machine type *to a
newer version* with the same chipset.

Paolo