[openstack-dev] [nova] A question about libvirt cpu mode=none configuration

park jianlonghei at gmail.com
Fri Mar 13 08:27:23 UTC 2015

hello Nova

By default, nova libvirt driver configuration for guest cpu as "cpu_mode 
= none",
you could add cpu features by changing flavor section as below, there 
will NOT
be any issues for this cmd.

$nova flavor-key m1.small set "capabilities:cpu_info:features"="<in> ***"
but, nova will ignore the cpu features after the guest boot up 
successfully, which
means the feature does NOT take effect(not be written into the xml for 
the guest).

And there is no message telling the users that the features does NOT 
take effect...
this may make the users confused...

if we add the feature into the xml file for the guest, this will trigger 
internal error
"libvirtError: XML error: Non-empty feature list specified without CPU 

so what should we do? Leave it as itself(ignore the users input, and 
boot the guest
successfully), or prompt the users with the errors?


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