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Description of problem:
Use setvcpus to hotplug vcpu for a guest, then the guest's CPU usage is 100% and guest hang there.
BTW, if set vcpu number to 0, it seems the error message is not correct.
Version-Release number of selected component (if applicable):
libvirt-0.9.10-21.el6_3.1.x86_64&libvirt-0.9.10-21.el6.x86_64
qemu-kvm-rhev-0.12.1.2-2.295.el6.x86_64
kernel-2.6.32-276.el6.x86_64
How reproducible:
100%
Steps to Reproduce:
1. Set the maximum cpu number to 4
#virsh dumpxml test
......
<vcpu placement='static' current='1'>4</vcpu>
.....
2. hotplug vcpus
#virsh setvcpus test 2
check the guest xml again
#virsh dumpxml test
......
<vcpu placement='static' current='2'>4</vcpu>
.....
3. After add step2, guest's CPU usage up to 100% and cann't conduct any operation in guest.
4. set vcpus to 0
# virsh setvcpus test 0
error: invalid argument: virDomainSetVcpus
Actual results:
As steps 3&4.
Expected results:
Hotplug vcpu can succeed, and the error message should be improved when set vcpu to 0.
Additional info:
No error meesages in libvirtd.log
There's either a bug or the the guest OS is missing support for CPU hotplug, so that it cannot handle the CPU that has emerged in the emulated system. This part of this bug isn't a problem with libvirt.
As of the error message, that probably is worth tweaking a little bit.