[Qemu-devel] [RFC PATCH v1 00/10] Core based CPU hotplug for PowerPC sPAPR

[Bharata B Rao <bharata@linux.vnet.ibm.com>]

Hi,

This is the next version of "Core based CPU hotplug for PowerPC sPAPR" that
was posted at
https://lists.gnu.org/archive/html/qemu-ppc/2016-02/msg00286.html

Here is a quick summary on how this approach is different from the
previous approaches that I have been pursuing with the last one being
v7 that posted here:
https://lists.gnu.org/archive/html/qemu-ppc/2016-01/msg00477.html

- Earlier approaches used an independent PowerPC specific core device while
  this approach uses an sPAPR specific core device that is derived from
  generic core device.
- The earlier approach didn't have the notion of where the boot time as
  well as hot-plugged cores would sit. In this approach QOM links are
  created from machine object to all possible core objects. While the
  links are set for boot time cores during machine init, the same is done
  for hotplugged cores at hotplug time. The name of this link property
  is standardized as "core[N]" since these links link the machine object
  with core devices. The link name ("core[N]") is used with core device's
  "slot" property to identify the QOM link to set for this core.
  (qemu) device_add spapr-cpu-core,id=core2,nr_threads=8,cpu_model=host,slot=core[2]
- The ealier approach created threads from instance_init of the core object
  using a modified cpu_generic_init() routine. It used smp_threads and
  MachineState->cpu_model globals. In the current approach, nr_threads and
  cpu_model are obtained as properties and threads are created from
  property setters. The thread objects are allocated as part of core
  device and object_initialize() is used to initialize them.

Some open questions remain:

- Does this device_add semantics look ok ?
  (qemu) device_add spapr-cpu-core,id=core2,nr_threads=8,cpu_model=host,slot=core[2]
- Is there need for machine to core object links ? If not, what would
  determine the slot/location of the core device ?
- How to fit this with CPUSlotProperties HMP interface that Igor is
  working on ?

This version has the following changes:

- Dropped QMP and HMP enumeration patches for now since it isn't clear
  if the approach I took would be preferrable by all archs. Will wait
  and see how Igor's patches evolve here.
- Added the following pre-req patches to support CPU removal:
  exec: Remove cpu from cpus list during cpu_exec_exit()
  exec: Do vmstate unregistration from cpu_exec_exit()
  cpu: Reclaim vCPU objects
  cpu: Add a sync version of cpu_remove()
- Added sPAPR CPU hot removal support
  xics,xics_kvm: Handle CPU unplug correctly
  spapr: CPU hot unplug support
- Moved up the "slot" property into abstract cpu-core device.
- Recover when thread creation fails (spapr_cpu_core_create_threads())
- cpu_model property in spapr-cpu-core deivce is now tracked using
  ObjectClass pointer instead of string.
- Fail topologies with incomplete cores from within sPAPR's machine init.
- Fixes in spapr-cpu-core object creation from machine init to create
  only boottime CPUs.
- Moved board specific wiring code for CPU threads (spapr_cpu_init)
  into core's realize method to be called after each thread's realization.
- No specific action under TYPE_CPU in ->plug() handler either for hotplug
  or hot removal.
- Moved all core related CPU hotplug routines into spapr_cpu_core.c where
  it truly belongs.
- Setting of NUMA node for hotplugged CPUs moved to spapr_cpu_init()).
- Compared to previous implementation of hot removal that was part of
  different series earlier, this implementation moves all core removal
  logic into spapr_cpu_core.c.
- Some minor cleanups like use of g_new0 instead of g_malloc0 etc.

This patchset is present at:
https://github.com/bharata/qemu/commits/spapr-cpu-core

Bharata B Rao (9):
  exec: Remove cpu from cpus list during cpu_exec_exit()
  exec: Do vmstate unregistration from cpu_exec_exit()
  cpu: Add a sync version of cpu_remove()
  cpu: Abstract CPU core type
  spapr: CPU core device
  spapr: Represent boot CPUs as spapr-cpu-core devices
  spapr: CPU hotplug support
  xics,xics_kvm: Handle CPU unplug correctly
  spapr: CPU hot unplug support

Gu Zheng (1):
  cpu: Reclaim vCPU objects

 cpus.c                          |  50 ++++++
 exec.c                          |  44 ++++-
 hw/cpu/Makefile.objs            |   1 +
 hw/cpu/core.c                   |  44 +++++
 hw/intc/xics.c                  |  14 ++
 hw/intc/xics_kvm.c              |   8 +-
 hw/ppc/Makefile.objs            |   1 +
 hw/ppc/spapr.c                  | 174 +++++++++++++++++--
 hw/ppc/spapr_cpu_core.c         | 361 ++++++++++++++++++++++++++++++++++++++++
 hw/ppc/spapr_events.c           |   3 +
 hw/ppc/spapr_rtas.c             |  24 +++
 include/hw/cpu/core.h           |  30 ++++
 include/hw/ppc/spapr.h          |   9 +
 include/hw/ppc/spapr_cpu_core.h |  42 +++++
 include/hw/ppc/xics.h           |   1 +
 include/qom/cpu.h               |  18 ++
 include/sysemu/kvm.h            |   1 +
 kvm-all.c                       |  57 ++++++-
 kvm-stub.c                      |   5 +
 19 files changed, 862 insertions(+), 25 deletions(-)
 create mode 100644 hw/cpu/core.c
 create mode 100644 hw/ppc/spapr_cpu_core.c
 create mode 100644 include/hw/cpu/core.h
 create mode 100644 include/hw/ppc/spapr_cpu_core.h

-- 
2.1.0