Description of problem:
When CPUs in host aren't equal.libvirt should  report error to user. Or successfully starting one guest will depends on the cpu' capabilities that libvirtd' work threads running on.

There is one test machine which has 4 cpus,but cpu0 doesn't have the monitor flag,and the other cpus have it.When start one guest with sandybridge cpu model . it will success when libvirtd' worker threads on cpu1-3 ,fail on cpu0.


Version-Release number of selected component (if applicable):
qemu-kvm-0.12.1.2-2.329.el6.x86_64
libvirt-0.10.2-7.el6.x86_64
kernel-2.6.32-335.el6.x86_6 

How reproducible:
100% 

Steps to Reproduce:
# for i in {1..5};do virsh capabilities|grep monitor|wc -l;done
1
1
0
0
0


# virsh capabilities  (There isn't the "monitor" feature ,libvirtd is running on cpu0, but host cpu 1-3 include it)
<capabilities>

<host>
<uuid>5bc55087-5efb-5107-6702-5133293b515f</uuid>
<cpu>
<arch>x86_64</arch>
<model>SandyBridge</model>
<vendor>Intel</vendor>
<topology sockets='1' cores='4' threads='1'/>
<feature name='osxsave'/>
<feature name='pdcm'/>
<feature name='xtpr'/>
<feature name='tm2'/>
<feature name='est'/>
<feature name='smx'/>
<feature name='vmx'/>
<feature name='ds_cpl'/>
<feature name='dtes64'/>
<feature name='pbe'/>
<feature name='tm'/>
<feature name='ht'/>
<feature name='ss'/>
<feature name='acpi'/>
<feature name='ds'/>
<feature name='vme'/>
</cpu>
......
<capabilities>


# virsh start rhel6.3-new
error: Failed to start domain rhel6.3-new
error: unsupported configuration: guest and host CPU are not compatible:
Host CPU does not provide required features: monitor


# virsh dumpxml rhel6.3-new  (There is the "monitor" feature)
<domain type='kvm'>
   ......
<cpu mode='custom' match='exact'>
<model fallback='allow'>SandyBridge</model>
<vendor>Intel</vendor>
<feature policy='require' name='tm2'/>
<feature policy='require' name='est'/>
<feature policy='require' name='monitor'/>
......
</cpu>
.....
</domain> 

Actual results:
When CPUs in host aren't equal , successfully  starting  one guest will depends on the cpu' capabilities that libvirtd'work threads running on. 

Expected results:
When CPUs in host aren't equal.libvirt should report error to user.


Additional info: