default or selected kernelversion does not have config value CONFIG_XEN_ACPI_HOTPLUG_CPU.
Result is shown for kernelversion 6.7.7

Xen ACPI cpu hotplug

modulename: xen-acpi-cpuhotplug.ko

configname: CONFIG_XEN_ACPI_HOTPLUG_CPU

Linux Kernel Configuration
└─>Device Drivers
└─>Xen driver support
└─>Xen ACPI cpu hotplug
In linux kernel since version 3.1 (release Date: 2011-10-24)  
Xen ACPI cpu enumerating and hotplugging

For hotplugging, currently Xen only support ACPI cpu hotadd.
If you want to hotadd cpu at runtime (the hotadded cpu cannot
be removed until machine stop), select Y/M here.

source code:
selects
CONFIG_ACPI_CONTAINER