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
Stefano Stabellini
2013-Jul-21 14:18 UTC
Re: [RFC] Improving CPU hotplug for 4.3 with qemu-xen
On Fri, 19 Jul 2013, Anthony PERARD wrote:> 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.These two commits worry me. I have a vague recollection that we hit both issues at some point in the past and we fixed them properly. I would rather have the proper fix than these two hacks if it''s possible.> 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
On Fri, Jul 19, 2013 at 4:26 PM, Anthony PERARD <anthony.perard@citrix.com> wrote:> 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 ?I think updates to the stable tree are now IanJ''s decision. It seems like this is an awful lot to backport. -George
George Dunlap writes ("Re: [Xen-devel] [RFC] Improving CPU hotplug for 4.3
with qemu-xen"):> On Fri, Jul 19, 2013 at 4:26 PM, Anthony PERARD
> <anthony.perard@citrix.com> wrote:
> > 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
Blimey.
> I think updates to the stable tree are now IanJ''s decision. It
seems
> like this is an awful lot to backport.
I agree. I don''t think this is really backport material.
Stefano, do you have an opinion ?
Ian.
Stefano Stabellini
2013-Aug-07 18:40 UTC
Re: [RFC] Improving CPU hotplug for 4.3 with qemu-xen
On Wed, 7 Aug 2013, Ian Jackson wrote:> George Dunlap writes ("Re: [Xen-devel] [RFC] Improving CPU hotplug for 4.3 with qemu-xen"): > > On Fri, Jul 19, 2013 at 4:26 PM, Anthony PERARD > > <anthony.perard@citrix.com> wrote: > > > 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 > > Blimey. > > > I think updates to the stable tree are now IanJ''s decision. It seems > > like this is an awful lot to backport. > > I agree. I don''t think this is really backport material. > Stefano, do you have an opinion ?I would prefer to avoid backporting all those patches. Especially if the errors above only show if a user asks for a vcpu to be plugged in when it''s actually already present.