Re: [patch 13/31] x86/fpu: Move KVMs FPU swapping to FPU core

Paolo Bonzini
2021-10-14T12:26:41Z

On 14/10/21 14:23, Thomas Gleixner wrote:
>> In principle I don't like it very much; it would be nicer to say "you
>> enable it for QEMU itself via arch_prctl(ARCH_SET_STATE_ENABLE), and for
>> the guests via ioctl(KVM_SET_CPUID2)". But I can see why you want to
>> keep things simple, so it's not a strong objection at all.
> Errm.
>
> qemu()
> read_config()
> if (dynamic_features_passthrough())
> request_permission(feature) <- prctl(ARCH_SET_STATE_ENABLE)
>
> create_vcpu_threads()
> ....
>
> vcpu_thread()
> kvm_ioctl(ENABLE_DYN_FEATURE, feature) <- KVM ioctl
>
> That's what I lined out, right?
>

I meant prctl for QEMU-in-user-mode vs. ioctl QEMU-in-guest-mode (i.e.
no prctl if only the guest uses it). But anyway it's just abstract
"beauty", let's stick to simple. :)

Paolo