[Qemu-devel] [RFC PATCH v1 0/5] sPAPR: Fix migration when CPUs are removed in random order

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

device_add/del based CPU hotplug and unplug support is upstream for
sPAPR PowerPC and is under development for x86. Both of these will
support CPU device removal in random order (and not necessarily in LIFO
order). Random order removal will result in holes in cpu_index range
which causes migration to fail. This needs fixes in both generic code
as well as arch specific code.

- migration_id is newly introduced and used as instance_id when registering
  CPU devices using vmstate_register. migration_id is set by the
  target machine code. To support forward migration, as per Igor's
  suggestion, this needs to be done conditionally based on machine type
  version.
- From pseries-2.7 onwards, we start using migration_id for migration as
  well as in XICS code.

vmstate registration calls are moved to cpu_common_realizefn and newly
introduced cpu_common_unrealizefn.

This patchset depends on Greg Kurz's patchset where among other things,
he is deriving cpu_dt_it (arch_id) based on core-id.
(https://lists.gnu.org/archive/html/qemu-devel/2016-07/msg00210.html)

Tested changes to XICS code with both kernel_irqchip=on/off.
This applies on ppc-for-2.7 branch of David's tree.

Changes in v1
-------------
- Introduced CPUState::migration_id to be used with vmstate_register()
- migration_id is now set by target machine code via
  CPUClass::get_migration_id()
- Use of migration is controlled by a property CPUState:use_migration_id.
- Use of SPAPR_COMPAT_2_6 to set use-migration-id property for all CPUs
  starting from pseries-2.7 onwards.
- Calling vmstate_[un]register() from cpu_common_[un]realizefn calls.

v0: http://lists.nongnu.org/archive/html/qemu-ppc/2016-07/msg00090.html

Bharata B Rao (5):
  cpu,target-ppc: Move cpu_vmstate_[un]register calls to
    cpu_common_[un]realize
  cpu: Introduce CPUState::migration_id
  spapr: Implement CPUClass::get_migration_id() for PowerPC CPUs
  xics: Use migration_id instead of cpu_index in XICS code
  cpu,spapr: Use migration_id from pseries-2.7 onwards

 exec.c                      | 54 ++++++++++++++++++++++++++++-----------------
 hw/intc/xics.c              | 12 ++++++----
 hw/intc/xics_kvm.c          | 11 +++++----
 hw/intc/xics_spapr.c        | 28 +++++++++++++++++------
 hw/ppc/spapr.c              |  5 +++++
 include/qom/cpu.h           |  8 +++++++
 qom/cpu.c                   | 29 ++++++++++++++++++++++++
 target-ppc/cpu-qom.h        |  2 ++
 target-ppc/translate_init.c | 15 +++++++++++++
 9 files changed, 127 insertions(+), 37 deletions(-)

-- 
2.7.4