Re: [PATCH v10 2/3] KVM: s390: guest support for topology function

[Nico Boehr <nrb@linux.ibm.com>]

Quoting Pierre Morel (2022-06-20 14:54:36)
[...]
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index 766028d54a3e..bb54196d4ed6 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
[...]
> @@ -3403,6 +3426,8 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
>         rc = kvm_s390_vcpu_setup(vcpu);
>         if (rc)
>                 goto out_ucontrol_uninit;
> +
> +       kvm_s390_sca_set_mtcr(vcpu->kvm);

We set the MTCR in the vcpu create. Does it also make sense to set it in kvm_arch_vcpu_destroy?

[...]
> diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
> index 12c464c7cddf..77a692238585 100644
> --- a/arch/s390/kvm/priv.c
> +++ b/arch/s390/kvm/priv.c
> @@ -873,10 +873,13 @@ static int handle_stsi(struct kvm_vcpu *vcpu)
[...]
> +       case 15:
> +               trace_kvm_s390_handle_stsi(vcpu, fc, sel1, sel2, operand2);
> +               insert_stsi_usr_data(vcpu, operand2, ar, fc, sel1, sel2);
> +               return -EREMOTE;

Maybe the API documentation should clearly note that once you turn on KVM_CAP_S390_CPU_TOPOLOGY, you will get exits to userspace for STSI 15.x.y, regardless of whether KVM_CAP_S390_USER_STSI is on or off.

Other than that, looks good, hence:

Reviewed-by: Nico Boehr <nrb@linux.ibm.com>