Description of problem:
After hotplug a vcpu in rhel9 guest, the new cpu was offline, it could be restore in online status after reboot the guest

Version-Release number of selected component (if applicable):
host kernel: 5.13.0-0.rc4.33.el9.s390x
guest kernel: 5.13.0-0.rc4.33.el9.s390x
qemu version: qemu-kvm-6.0.0-5.el9.s390x

How reproducible:
100%

Steps to Reproduce:
1. Boot up a guest with
/usr/libexec/qemu-kvm \
 -name 'avocado-vt-vm1' \
 -sandbox on \
 -machine s390-ccw-virtio \
 -nodefaults \
 -vga none \
 -m 3072 \
 -smp 5,maxcpus=6,cores=3,threads=1,sockets=2  \
 -cpu 'host' \
 -chardev socket,id=qmp_id_qmpmonitor1,server,path=/var/tmp/avocado_1,nowait \
 -mon chardev=qmp_id_qmpmonitor1,mode=control \
 -chardev socket,id=chardev_serial0,server,path=/tmp/bfu,nowait \
 -device sclpconsole,id=serial0,chardev=chardev_serial0 \
 -device virtio-scsi-ccw,id=virtio_scsi_ccw0 \
 -blockdev node-name=file_image1,driver=file,aio=threads,filename=/home/bfu/kar/vt_test_images/rhel900-s390x-virtio-scsi.qcow2,cache.direct=on,cache.no-flush=off \
 -blockdev node-name=drive_image1,driver=qcow2,cache.direct=on,cache.no-flush=off,file=file_image1 \
 -device virtio-blk-ccw,id=image1,drive=drive_image1,write-cache=on \
 -device virtio-net-ccw,mac=9a:9f:19:fe:49:13,id=idh8Nq82,netdev=idVx9QzC \
 -netdev tap,id=idVx9QzC,vhost=on \
 -nographic \
 -rtc base=utc \
 -boot strict=on \
 -enable-kvm \
 -device virtio-mouse-ccw,id=input_mouse1 \
 -device virtio-keyboard-ccw,id=input_keyboard1 \
 -qmp stdio

2. Hotplug a vcpu as follow commands
 {"execute": "qmp_capabilities", "id": "y5bmzGU1"}
{"return": {}, "id": "y5bmzGU1"}
{"execute": "device_add", "arguments": {"id": "main_vcpu", "core-id": "0", "driver": "host-s390x-cpu"}, "id": "PgXcu7UJ"}
{"id": "PgXcu7UJ", "error": {"class": "GenericError", "desc": "Unable to add CPU with core-id: 0, it already exists"}}
{"execute": "device_add", "arguments": {"id": "vcpu1", "driver": "host-s390x-cpu", "core-id": 5}, "id": "bsi4CWYq"}
{"return": {}, "id": "bsi4CWYq"}

3.Check number of vcpu as follow commands:
[root@localhost ~]# grep -c "^processor\b" /proc/cpuinfo
5


Actual results:
[root@localhost ~]# grep -c "^processor\b" /proc/cpuinfo
5

Expected results:
[root@localhost ~]# grep -c "^processor\b" /proc/cpuinfo
6

Additional info: