[Qemu-devel] [RFC 0/3] fix migration issues after hotplug a discontinuous cpuid

[Chen Fan]

At present, after hotplug a discontinuous cpu id on source side, then done
migration, hotplug again will fail on destination side. for example:
on source side:
   1) boot with -smp 1,maxcpus=4    
   2) cpu-add id=2
   3) live-migration
on destination side:
   1) boot with -smp 2,maxcpus=4
   1) cpu-add id=1

the root cause is the generated apicid is sequential from 0 to smp_cpus when
initialize cpus at booting time on destination side, there apicid will be 0 
and 1, but on source side the existed apicid after hotplug are 0 and 2.
so if add cpu with id=1, this will show error with this cpu alreay exists.

this patches added -smp X,apics=0x option to specify apic map. follow above
example:
on destination side:
   1) boot with -smp 2,maxcpus=4,apics=0xA
this apics value is a hex number as existed apicid bitmap, 0xA is 1010B for
apicid are 0 and 2.

this patches will be helpful for arbitrary CPU hot-remove as well.

Chen Fan (3):
  target-i386: moving registers of vmstate from cpu_exec_init() to
    x86_cpu_realizefn()
  target-i386: add -smp X,apics=0x option
  target-i386: add qmp command 'query-cpus' to display apic_id

 cpus.c                  |  1 +
 exec.c                  |  5 ++++
 hw/i386/pc.c            |  9 +++++--
 include/sysemu/sysemu.h |  4 ++++
 qapi-schema.json        |  4 +++-
 qemu-options.hx         | 15 +++++++++---
 target-i386/cpu.c       |  9 +++++++
 vl.c                    | 62 ++++++++++++++++++++++++++++++++++++++++++++++++-
 8 files changed, 102 insertions(+), 7 deletions(-)

-- 
1.8.1.4