Re: [Qemu-arm] [Qemu-devel] [PATCH v2 11/14] target/arm/kvm64: max cpu: Enable SVE when available

[Andrew Jones]

On Wed, Jun 26, 2019 at 01:09:45PM +0200, Richard Henderson wrote:
> On 6/21/19 6:34 PM, Andrew Jones wrote:
> > @@ -675,6 +689,11 @@ static void aarch64_max_initfn(Object *obj)
> >  
> >      if (kvm_enabled()) {
> >          kvm_arm_set_cpu_features_from_host(cpu);
> > +        /*
> > +         * KVM doesn't yet support the sve-max-vq property, but
> > +         * setting cpu->sve_max_vq is also used to turn SVE on.
> > +         */
> > +        cpu->sve_max_vq = ARM_SVE_INIT;
> 
> Can we support this value with KVM_GET/SET_ONE_REG on ZCR_EL2?  (IIRC KVM
> requires VHE to support SVE, so the host is always EL2 and the guest is always
> EL1.)
> 
> Or do we need to probe this via normal userland prctl?
> 
> Or am I getting ahead of the patches to follow?

Hopefully mostly this, because I didn't understand the concern with VHE.
If it still looks like something is missing after looking at other
patches, then please come back to this to help me understand.

Thanks,
drew