LoongArch cpu hotplug is based on ACPI GED device, there is a little
change about ipi and extioi device, the value of num-cpu property is
maximum cpu number rather than present cpu number.

It can be verified with qemu command:
  qemu-system-loongarch64 -smp 2,maxcpus=16,sockets=4,cores=4,threads=1
and vcpu can be added or remove with hmp command:
  device_add la464-loongarch-cpu,socket-id=0,core-id=2,thread-id=0,id=cpu-2
  device_del cpu-2

---
v2 ... v3:
  1. Use qdev_realize_and_unref() with qdev_realize() and object_unref().
  2. Set vcpus_count with 1 since vcpu object is created for every thread.
  3. Remove property hw-id, use internal variable hw_id to differentiate
     cold-plug cpus and hot-plug cpus.
  4. Add generic function virt_init_cpu_irq() to init interrupt pin
     of CPU object, used by both cold-plug and hot-plug CPUs

v1 ... v2:
  1. Add new property hw-id, property hw-id is set for cold-added CPUs,
     and property socket-id/core-id/thread-id is set for hot-added CPUs.
     The two properties can be generated from each other.
  2. Use general hotplug api such as hotplug_handler_pre_plug etc
  3. Reorganize the patch order, split the patch set into 4 small
     patches.
---
Bibo Mao (5):
  hw/loongarch/virt: Add CPU topology support
  hw/loongarch/virt: Implement cpu plug interface
  hw/loongarch/virt: Add generic function to init interrupt pin of CPU
  hw/loongarch/virt: Update the ACPI table for hotplug cpu
  hw/loongarch/virt: Enable cpu hotplug feature on virt machine

 docs/system/loongarch/virt.rst |  31 +++
 hw/loongarch/Kconfig           |   1 +
 hw/loongarch/acpi-build.c      |  35 +++-
 hw/loongarch/virt.c            | 349 +++++++++++++++++++++++++++++----
 include/hw/loongarch/virt.h    |   3 +
 target/loongarch/cpu.c         |  25 +++
 target/loongarch/cpu.h         |  17 ++
 7 files changed, 416 insertions(+), 45 deletions(-)


base-commit: 92ec7805190313c9e628f8fc4eb4f932c15247bd
-- 
2.39.3