Re: [Qemu-devel] [RFC qom-cpu v4 00/10] i386: add cpu hot remove support

[Igor Mammedov]

On Wed, 04 Dec 2013 10:15:16 +0800
Chen Fan <address@hidden> wrote:

> On Thu, 2013-11-28 at 15:41 +0100, Igor Mammedov wrote:
> > On Wed, 9 Oct 2013 17:43:08 +0800
> > Chen Fan <address@hidden> wrote:
> > 
> > > Via implementing ACPI standard methods _EJ0 in bios, after Guest OS hot 
> > > remove
> > > one vCPU, it is able to send a signal to QEMU, then QEMU could notify
> > > the assigned vCPU of exiting. meanwhile, and intruduce the QOM command 
> > > 'cpu-del' to remove
> > > vCPU from QEMU itself.
> > 
> > have you tried following sequence:
> > cpu-add 1
> > cpu-add 2
> > cpu-del 1
> > and then do migration?
> Hi, Igor, Thanks for your test case. I had test the above sequence, when
> I add two vcpu, then delete the first one, I found command 'lscpu' show:
> CPU(s):                 1
> On-line CPU(s） list:   0,2
> off -line CPU(s) list:  
> 
> I know it is wrong, but I want to know which is expected to show, A or
> B?
> A:
> CPU(s):               2
> On-line CPU(s） list:   0,2
> off -line CPU(s) list:
> 
> B:
> CPU(s):               2
> On-line CPU(s） list:   0,1
> off -line CPU(s) list:
> 

if you deleted #1 CPU than A is correct.

There is certain thing that depend on cpu_index in QEMU code base,
migration is one of them. It should break if for arbitrary CPU removal/addition
is introduced.

> Thanks,
> Chen
> 
> > 
> > > 
> > > this work is based on Andreas Färber's qom-cpu branch tree.
> > >     git://github.com/afaerber/qemu-cpu.git
> > > 
> > > this series patches must be used with seabios patch and KVM patch 
> > > together.
> > > 
> > > for KVM patches:
> > >     http://comments.gmane.org/gmane.comp.emulators.kvm.devel/114347
> > > 
> > > for seabios patches:
> > >     http://comments.gmane.org/gmane.comp.emulators.qemu/230460
> > > 
> > > Chen Fan (10):
> > >   x86: move apic_state field from CPUX86State to X86CPU
> > >   apic: remove redundant variable 'apic_no' from apic_init_common()
> > >   apic: remove local_apics array and using CPU_FOREACH instead
> > >   x86: add x86_cpu_unrealizefn() for cpu apic remove
> > >   qmp: add 'cpu-del' command support
> > >   qom cpu: rename variable 'cpu_added_notifier' to
> > >     'cpu_hotplug_notifier'
> > >   qom cpu: add UNPLUG cpu notifier support
> > >   i386: implement pc interface pc_hot_del_cpu()
> > >   piix4: implement function cpu_status_write() for vcpu ejection
> > >   cpus: reclaim allocated vCPU objects
> > > 
> > >  cpu-exec.c                      |  2 +-
> > >  cpus.c                          | 51 +++++++++++++++++++++--
> > >  hw/acpi/piix4.c                 | 66 ++++++++++++++++++++++++------
> > >  hw/i386/kvm/apic.c              | 18 +++++++-
> > >  hw/i386/kvmvapic.c              |  8 ++--
> > >  hw/i386/pc.c                    | 51 ++++++++++++++++++-----
> > >  hw/i386/pc_piix.c               |  3 +-
> > >  hw/intc/apic.c                  | 91 
> > > ++++++++++++++++++++++-------------------
> > >  hw/intc/apic_common.c           | 17 ++------
> > >  include/hw/boards.h             |  2 +
> > >  include/hw/i386/apic_internal.h |  6 +--
> > >  include/hw/i386/pc.h            |  1 +
> > >  include/qom/cpu.h               | 20 +++++++++
> > >  include/sysemu/kvm.h            |  1 +
> > >  include/sysemu/sysemu.h         |  2 +-
> > >  kvm-all.c                       | 25 +++++++++++
> > >  qapi-schema.json                | 12 ++++++
> > >  qmp-commands.hx                 | 23 +++++++++++
> > >  qmp.c                           |  9 ++++
> > >  qom/cpu.c                       | 26 +++++++++---
> > >  target-i386/cpu-qom.h           |  5 +++
> > >  target-i386/cpu.c               | 57 ++++++++++++++++++++------
> > >  target-i386/cpu.h               |  4 --
> > >  target-i386/helper.c            |  9 ++--
> > >  target-i386/kvm.c               | 23 +++++------
> > >  target-i386/misc_helper.c       |  8 ++--
> > >  26 files changed, 403 insertions(+), 137 deletions(-)
> > > 
> > 
> 
>