Re: [Qemu-devel] [PATCH v9 0/7] Allow hotplug of s390 CPUs

[Cornelia Huck <cornelia.huck@de.ibm.com>]

On Fri,  4 Mar 2016 12:34:28 -0500
Matthew Rosato <mjrosato@linux.vnet.ibm.com> wrote:

> As discussed in the KVM call, we will go ahead with cpu_add for 
> s390x to get cpu hotplug functionality in s390x now, until
> architectures that require a more robust hotplug interface
> settle on a design.
> 
> To configure a guest with 2 CPUs online at 
> boot and 4 maximum:
> 
> qemu -smp 2,maxcpus=4
> 
> Or, when using libvirt:
>   <domain>
>     ...
>     <vcpu current="2">4</vcpu>
>     ...
>   </domain> 
> 
> 
> To subsequently hotplug a CPU:
> 
> Issue 'cpu-add <id>' from qemu monitor, or use virsh setvcpus --count <n> 
> <domain>, where <n> is the total number of desired guest CPUs.
> 
> At this point, the guest must bring the CPU online for use -- This can be 
> achieved via "echo 1 > /sys/devices/system/cpu/cpuX/online" or via a management 
> tool like cpuplugd.
> 
> This patch set is based on work previously done by Jason Herne.
> 
> Matthew Rosato (7):
>   s390x/cpu: Cleanup init in preparation for hotplug
>   s390x/cpu: Set initial CPU state in common routine
>   s390x/cpu: Get rid of side effects when creating a vcpu
>   s390x/cpu: Tolerate max_cpus
>   s390x/cpu: Add CPU property links
>   s390x/cpu: Add error handling to cpu creation
>   s390x/cpu: Allow hotplug of CPUs
> 
>  hw/s390x/s390-virtio-ccw.c | 46 +++++++++++++++++++++-
>  hw/s390x/s390-virtio.c     | 36 +++++++++--------
>  hw/s390x/s390-virtio.h     |  2 +-
>  target-s390x/cpu-qom.h     |  3 ++
>  target-s390x/cpu.c         | 96 +++++++++++++++++++++++++++++++++++++++++++---
>  target-s390x/cpu.h         |  2 +
>  target-s390x/helper.c      | 41 +++++++++++++++++++-
>  7 files changed, 200 insertions(+), 26 deletions(-)

Thanks, applied to my s390-next branch.