Re: [GIT PULL 4/4] KVM: s390: Support keyless subset guest mode

[David Hildenbrand <david@redhat.com>]

> diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
> index 025b1f2..4719ecb 100644
> --- a/arch/s390/kvm/vsie.c
> +++ b/arch/s390/kvm/vsie.c
> @@ -117,6 +117,8 @@ static int prepare_cpuflags(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>  		newflags |= cpuflags & CPUSTAT_SM;
>  	if (test_kvm_cpu_feat(vcpu->kvm, KVM_S390_VM_CPU_FEAT_IBS))
>  		newflags |= cpuflags & CPUSTAT_IBS;
> +	if (test_kvm_cpu_feat(vcpu->kvm, KVM_S390_VM_CPU_FEAT_KSS))
> +		newflags |= cpuflags & CPUSTAT_KSS;
>  
>  	atomic_set(&scb_s->cpuflags, newflags);
>  	return 0;
> @@ -289,7 +291,9 @@ static int shadow_scb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>  	 * bits. Therefore we cannot provide interpretation and would later
>  	 * have to provide own emulation handlers.
>  	 */
> -	scb_s->ictl |= ICTL_ISKE | ICTL_SSKE | ICTL_RRBE;
> +	if (!(atomic_read(&scb_s->cpuflags) & CPUSTAT_KSS))
> +		scb_s->ictl |= ICTL_ISKE | ICTL_SSKE | ICTL_RRBE;
> +
What would actually happen, if ICTL_ISKE | ICTL_SSKE | ICTL_RRBE remain
set? I assume KSS will dominate? Or are there any validity interceptions
defined for this?

-- 

Thanks,

David