Re: [PATCH] KVM: s390: provide a capability for AIS state migration

[Cornelia Huck <cohuck@redhat.com>]

On Thu,  9 Nov 2017 10:04:04 +0100
Christian Borntraeger <borntraeger@de.ibm.com> wrote:

> The AIS capability was introduced in 4.12, while the interface
> to migrate the state was added in 4.13. Let's add a new capability
> that tells userspace that AIS states can be migrated.

I think that needs a bit more explanation (i.e., why can't userspace
check for the migration interface?) Also, it would be good to mention
the cap under Documentation/.

[It's very likely that we will have forgotten the history of this in
in a few month's time...]

> 
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---
>  arch/s390/kvm/kvm-s390.c | 1 +
>  include/uapi/linux/kvm.h | 1 +
>  2 files changed, 2 insertions(+)
> 
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index de6a5b7..8f4b655 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -395,6 +395,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>  	case KVM_CAP_S390_USER_INSTR0:
>  	case KVM_CAP_S390_CMMA_MIGRATION:
>  	case KVM_CAP_S390_AIS:
> +	case KVM_CAP_S390_AIS_MIGRATION:
>  		r = 1;
>  		break;
>  	case KVM_CAP_S390_MEM_OP:
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 8388875..b605956 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -930,6 +930,7 @@ struct kvm_ppc_resize_hpt {
>  #define KVM_CAP_PPC_SMT_POSSIBLE 147
>  #define KVM_CAP_HYPERV_SYNIC2 148
>  #define KVM_CAP_HYPERV_VP_INDEX 149
> +#define KVM_CAP_S390_AIS_MIGRATION 150
>  
>  #ifdef KVM_CAP_IRQ_ROUTING
>