On ppc64, the PowerVM hypervisor runs with limited memory and a VCPU
creation during hotplug may fail during kvm_ioctl for KVM_CREATE_VCPU,
leading to termination of guest since errp is set to &error_fatal while
calling kvm_init_vcpu. This unexpected behaviour can be avoided by
pre-creating and parking vcpu on success or return error otherwise.
This enables graceful error delivery for any vcpu hotplug failures while
the guest can keep running.

This series adds another helper to create and park vcpu (based on below
patch by Salil), exports cpu_get_free_index to be reused later and adds
ppc arch specfic handling for vcpu hotplug failure using kvm accel
helper cpu_target_realize.

Based on api refactoring to create/park vcpus introduced in 1/8 of patch series:
https://lore.kernel.org/qemu-devel/20240522211111.232114-1-salil.mehta@huawei.com/

Changelog:
v3: Addressed review comments from Nick
v2: Addressed review comments from Nick
v1: Initial patch

Harsh Prateek Bora (3):
  accel/kvm: Introduce kvm_create_and_park_vcpu() helper
  cpu-common.c: export cpu_get_free_index to be reused later
  target/ppc: handle vcpu hotplug failure gracefully

 accel/kvm/kvm-cpus.h      |  8 ++++++++
 include/exec/cpu-common.h |  2 ++
 accel/kvm/kvm-all.c       | 12 ++++++++++++
 cpu-common.c              |  7 ++++---
 target/ppc/kvm.c          | 41 +++++++++++++++++++++++++++++++++++++++
 5 files changed, 67 insertions(+), 3 deletions(-)

-- 
2.39.3