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

park jianlonghei at gmail.com
Fri Mar 13 13:38:26 UTC 2015

On 2015年03月13日 20:42, Steve Gordon wrote:
> ----- Original Message -----
>> From: "park" <jianlonghei at gmail.com>
>> To: "OpenStack Development Mailing List (not for usage questions)" <openstack-dev at lists.openstack.org>
>> 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...
> This issue is more general than the cpu_mode=none case, in that the capabilities filter is filtering *hosts* based on their CPU features. As you have discovered, whether they are actually exposing those features to guests in their current configuration is not taken into account (that is, cpu_mode/cpu_model settings aren't considered at all). Ideally they would be, but I'm not sure this is trivial.
and I think the CPU configuration should take effect,
otherwise, users should be prompted some messages..
> -Steve
>> 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
>> model"
>> 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?
>> Thanks
>>       Park
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