Re: arm: "max" CPU class hierarchy changes possible?

[Peter Maydell]

On Thu, 11 Mar 2021 at 17:16, Claudio Fontana <cfontana@suse.de> wrote:
> Maybe Peter you could clarify similarly what the intended meaning of "max" is 
> on ARM?

"max" is "best we can do, whatever that is". (On KVM this is "same as
the host".)
"host" is "whatever the host is (KVM only)".

> KVM: (aarch64-only): aarch64_max_initfn():
>
> The following comment in the code seems wrong to me:
>
> /* -cpu max: if KVM is enabled, like -cpu host (best possible with this 
> host); */
>
> This is not exactly true:
>
> "-cpu max" calls kvm_arm_set_cpu_features_from_host(), (which checks 
> "dtb_compatible", and if not set gets the features from the host, if set ...?)
> After that, calls aarch64_add_sve_properties() and then adds also 
> "svw-max-vq". This code is common with TCG.
>
> In the case of cpu host instead,
>
> "-cpu host" calls kvm_arm_set_cpu_features_from_host(), same as max, then 
> calls aarch64_add_sve_properties() but does NOT add "svw-max-vq".
>
> Is this a bug?

Maybe; that's a question for Richard or Drew...

> Are "max" and "host" for KVM supposed to be the same like with x86?

Yes.

thanks
-- PMM