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

[Paolo Bonzini]

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