CPU Hotplug (Host Model) Causes the Windows VM to BSOD
Description of problem:
The QEMU runs on a host with the Intel(R) Xeon(R) CPU E3-1230 v6 CPU which supports Software Guard Extension (SGX). I start a VM with Windows Server 2019 inside and with `-cpu host,...`. When I attempts to hotplug additional CPU (when the VM is running), the OS issues a bug check 0x3e (`MULTIPROCESSOR_CONFIGURATION_NOT_SUPPORTED`). The problem is that the newly hotplugged CPU is not evaluated as "equivalent enough" compared to the already present CPUs. I did some more digging and reverse engineering and it looks like the CPU being hotplugged has SGX turned off. This seems to be fixed when the VM reboots.

I tried to disable SGX through `-cpu host,-sgx` which helps (the VM successfully accepts the hotplugged CPU), however, `+sgx` does not help (seems to have no effect on the CPU being hotplugged).

My goal is to be able to hotplug CPUs even when the host CPU supports SGX.

I tested with QEMU 8.0.0, 9.1.0, 9.1.1 and 9.1.50 (current master) but with no luck.
Steps to reproduce:
1. Create a simple Windows VM,
2. start the VM,
3. use `qpm-shell` to hotplug a CPU (https://www.qemu.org/docs/master/system/cpu-hotplug.html).

I can provide you the VM as well but its image (QCOW2) has around 10G in size.

Best regards
Martin Dráb