[RFC] Improving CPU hotplug for 4.3 with qemu-xen

[Anthony PERARD <anthony.perard@citrix.com>]

Hi,

The cpu hotplug that have been backported from QEMU to qemu-xen (1.5 to
1.3) is incomplete. Especially, there is no way to know if a CPU is
already marked as online by qemu. This result by those error messages
from libxl:

libxl: error: libxl_qmp.c:289:qmp_handle_error_response: received an
error message from QMP server: Unable to add CPU: 0, it already exists
libxl: error: libxl_qmp.c:289:qmp_handle_error_response: received an
error message from QMP server: Unable to add CPU: 1, it already exists

So I tried to backport more patches so it will become possible for libxl
to get the list of online cpu.

But this result in *a lot* of patches.

Here is the git tree and see the list of patches at the end of the mail:
git://xenbits.xen.org/people/aperard/qemu-dm.git  backport-cpu-device

There is still some work to be done like making sure everything is
working properly and making some patches to use it with libxl.

So George, is it worth getting those patches into Xen 4.3 to get ride of
the error message ?



cpu: Change parent type to Device
qdev: Fold state enum into bool realized
qdev: Prepare "realized" property
cpu: Prepare QOM realizefn
target-i386: Update X86CPU to QOM realizefn
cpu: Introduce cpu_resume(), for single CPU
target-i386: Split out CPU creation and features parsing
cpu: Resume CPU from DeviceClass::realize() if hot-plugged
Revert "xen: Implement hot_add_cpu hook."
Revert "acpi_piix4: Add infrastructure to send CPU hot-plug GPE to guest"
cpu: Introduce CPU hot-plug notifier
cpu: Add helper cpu_exists(), to check if CPU with specified id exists
acpi_piix4: Add infrastructure to send CPU hot-plug GPE to guest
target-i386: Introduce feat2prop() for CPU properties
target-i386: Introduce apic-id CPU property
target-i386: Do not allow to set apic-id once CPU is realized
target-i386: Replace MSI_SPACE_SIZE with APIC_SPACE_SIZE
qapi/qmp-registry.c: Include headers it needs
qga/channel-posix.c: Include headers it needs
user: Move *-user/qemu-types.h to main directory
user: Rename qemu-types.h to qemu-user-types.h
Create qemu-types.h for struct typedefs
qlist.h: Do not include qemu-common.h
sysbus: make SysBusDeviceClass::init optional
target-i386: Introduce ICC bus/device/bridge
target-i386: Attach ICC bus to CPU on its creation
a fix for cpu_x86_create
fix machine initialization.
extract/unify the constant 0xfee00000 as APIC_DEFAULT_ADDRESS
kvmvapic: Make dependency on sysbus.h explicit
target-i386: Move APIC to ICC bus
pc: Implement QEMUMachine::hot_add_cpu hook



-- 
Anthony PERARD