Jordan Niethe [off-list ref] writes:

A series of hcalls have been added to the PAPR which allow a regular
guest partition to create and manage guest partitions of its own. KVM
already had an interface that allowed this on powernv platforms. This
existing interface will now be called "nestedv1". The newly added PAPR
interface will be called "nestedv2".  PHYP will support the nestedv2
interface. At this time the host side of the nestedv2 interface has not
been implemented on powernv but there is no technical reason why it
could not be added.

Some build errors with powernv_defconfig, I haven't dug into them but
presumably some ifdefs needed.

  ../arch/powerpc/kvm/book3s_hv_nestedv2.c: In function ‘kvmhv_nestedv2_vcpu_create’:
  ../arch/powerpc/kvm/book3s_hv_nestedv2.c:954:14: error: implicit declaration of function ‘plpar_guest_create_vcpu’ [-Werror=implicit-function-declaration]
    954 |         rc = plpar_guest_create_vcpu(0, vcpu->kvm->arch.lpid, vcpu->vcpu_id);
        |              ^~~~~~~~~~~~~~~~~~~~~~~
  ../arch/powerpc/kvm/guest-state-buffer.c: In function ‘kvmppc_gsb_send’:
  ../arch/powerpc/kvm/guest-state-buffer.c:592:14: error: implicit declaration of function ‘plpar_guest_set_state’ [-Werror=implicit-function-declaration]
    592 |         rc = plpar_guest_set_state(hflags, gsb->guest_id, gsb->vcpu_id,
        |              ^~~~~~~~~~~~~~~~~~~~~
  ../arch/powerpc/kvm/guest-state-buffer.c: In function ‘kvmppc_gsb_recv’:
  ../arch/powerpc/kvm/guest-state-buffer.c:617:14: error: implicit declaration of function ‘plpar_guest_get_state’ [-Werror=implicit-function-declaration]
    617 |         rc = plpar_guest_get_state(hflags, gsb->guest_id, gsb->vcpu_id,


cheers