There is an existing Nested-HV API to enable nested guests on powernv
machines. However, that is not supported on pseries/PowerVM LPARs.
This patch series implements required hcall interfaces to enable nested
guests with KVM on PowerVM.
Unlike Nested-HV, with this API, entire L2 state is retained by L0
during guest entry/exit and uses pre-defined Guest State Buffer (GSB)
format to communicate guest state between L1 and L2 via L0.

L0 here refers to the phyp/PowerVM, or launching a Qemu TCG L0 with the
newly introduced option cap-nested-papr=true.
L1 refers to the LPAR host on PowerVM or Linux booted on Qemu TCG with
above mentioned option cap-nested-papr=true.
L2 refers to nested guest running on top of L1 using KVM.
No SW changes needed for Qemu running in L1 Linux as well as L2 Kernel.

Linux Kernel side support is already merged upstream:
---
commit 19d31c5f115754c369c0995df47479c384757f82
Author: Jordan Niethe <jniethe5@gmail.com>
Date:   Thu Sep 14 13:05:59 2023 +1000

    KVM: PPC: Add support for nestedv2 guests
---
For more details, documentation can be referred in either of patch
series.

There are scripts available to assist in setting up an environment for
testing nested guests at https://github.com/iamjpn/kvm-powervm-test

A tree with this series is available at:
https://github.com/planetharsh/qemu/tree/upstream-0219-v4

Thanks to Michael Neuling, Shivaprasad Bhat, Amit Machhiwal, Kautuk
Consul, Vaibhav Jain and Jordan Niethe.

Changelog:
v4: added hcall unreg helper to allow hcall re-registrations in caps apply.
v3: https://lore.kernel.org/qemu-devel/20240118052438.1475437-1-harshpb@linux.ibm.com/
v2: https://lore.kernel.org/qemu-devel/20231012104951.194876-1-harshpb@linux.ibm.com/
v1: https://lore.kernel.org/qemu-devel/20230906043333.448244-1-harshpb@linux.ibm.com/

Amit Machhiwal (1):
  spapr: nested: Set the PCR when logical PVR is set

Harsh Prateek Bora (14):
  spapr: nested: register nested-hv api hcalls only for cap-nested-hv
  spapr: nested: move nested part of spapr_get_pate into spapr_nested.c
  spapr: nested: Introduce SpaprMachineStateNested to store related
    info.
  spapr: nested: keep nested-hv related code restricted to its API.
  spapr: nested: Document Nested PAPR API
  spapr: nested: Introduce H_GUEST_[GET|SET]_CAPABILITIES hcalls.
  spapr: nested: Introduce H_GUEST_[CREATE|DELETE] hcalls.
  spapr: nested: Introduce H_GUEST_CREATE_VCPU hcall.
  spapr: nested: Extend nested_ppc_state for nested PAPR API
  spapr: nested: Initialize the GSB elements lookup table.
  spapr: nested: Introduce H_GUEST_[GET|SET]_STATE hcalls.
  spapr: nested: Use correct source for parttbl info for nested PAPR
    API.
  spapr: nested: Introduce H_GUEST_RUN_VCPU hcall.
  spapr: nested: Introduce cap-nested-papr for Nested PAPR API

 docs/devel/nested-papr.txt    |  514 +++++++++++
 include/hw/ppc/spapr.h        |   26 +-
 include/hw/ppc/spapr_nested.h |  430 ++++++++-
 target/ppc/cpu.h              |    4 +
 hw/ppc/ppc.c                  |   10 +
 hw/ppc/spapr.c                |   35 +-
 hw/ppc/spapr_caps.c           |   59 ++
 hw/ppc/spapr_hcall.c          |   24 +-
 hw/ppc/spapr_nested.c         | 1552 ++++++++++++++++++++++++++++++++-
 9 files changed, 2599 insertions(+), 55 deletions(-)
 create mode 100644 docs/devel/nested-papr.txt

-- 
2.39.3