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This bug has been copied from bug #1162080 and has been proposed
to be backported to 7.1 z-stream (EUS).

Reproduced bug with qemu-kvm-rhev-2.1.2-23.el7.x86_64 & win2012-64r2 guest.

Verified this bug with qemu-kvm-rhev-2.1.2-23.el7_1.1 & win2008r2 & win2012r2.

step:
hotplug 64 vcpu to guest via qmp.  all vcpus can be found in Task Manager.

so, This bug is fixed.

Additional, QE tested some other scenarios for regression test. all scenarios works well.

S1. reboot guest after hotplug vcpu 

S2. shutdown guest after hotplug vcpu

S3. hotplug 240 vcpu to guest
    can see all vcpus in task manager for win2012r2 guest.

S4. hotplug existing vcpu

S5. hotplug vcpu number >Max support(240) 

S6. hotplug illegal vcpu number

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2015-0677.html