Re: [PATCH RFCv2 00/20] kvm/arm: Introduce a customizable aarch64 KVM host model

[Daniel P . Berrangé]

On Thu, Dec 12, 2024 at 09:12:33AM +0100, Eric Auger wrote:
> Connie,
> 
> On 12/6/24 12:21, Cornelia Huck wrote:
> > A respin/update on the aarch64 KVM cpu models. Also available at
> > gitlab.com/cohuck/qemu arm-cpu-model-rfcv2

snip

> From a named model point of view, since I do not see much traction
> upstream besides Red Hat use cases, targetting ARM spec revision
> baselines may be overkill. Personally I would try to focus on above
> models: AltraMax, AmpereOne, Grace, ... Or maybe the ARM cores they may
> be derived from.

If we target modelling of vendor named CPU models, then beware that
we're opening the door to an very large set (potentially unbounded)
of named CPU models over time. If we target ARM spec baselines then
the set of named CPU models is fairly modest and grows slowly.

Including ARM spec baselines will probably reduce the demand for
adding vendor specific named models, though I expect we'll still
end up wanting some, or possibly even many.

Having some common baseline models is likely useful for mgmt
applications in other ways though.

Consider you mgmt app wants to set a CPU model that's common across
heterogeneous hardware. They don't neccessarily want/need to be
able to live migrate between heterogeneous CPUs, but for simplicity
of configuration desire to set a single named CPU across all guests,
irrespective of what host hey are launched on. The ARM spec baseline
named models would give you that config simplicity.

With regards,
Daniel
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