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

[Andreas Färber]

Am 23.06.2015 um 18:25 schrieb Daniel P. Berrange:
> Whether QEMU changed the CPU for existing machines, or only for new
> machines is actually not the core problem. Even if we only changed
> the CPU in new machines that would still be an unsatisfactory situation
> because we want to be able to be able to access different versions of
> the CPU without the machine type changing, and access different versions
> of the machine type, without the CPU changing. IOW it is the fact that the
> changes in CPU are tied to changes in machine type that is the core
> problem.

This coupling is by design and we expect all KVM/QEMU users to adhere to
it, including those that use the libvirt tool (which I assume is going
to be the majority of KVM users). Either you want a certain
backwards-compatible machine and CPU, or you want the latest and
greatest - why in the world mix and match?!

Would a qemu64-2.3 model help here that pc*-2.3 could use? I believe
that's been proposed in the past. I don't oppose the idea of a
fully-custom CPU, but this blatant attempt of ignoring QEMU's CPU
versioning by libvirt worries me.

Regards,
Andreas

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