[libvirt] Hyervisor Features elements

[Michal Privoznik]

On 13.09.2014 17:21, bancfc at openmailbox.org wrote:
> Hello. Under Hypevisor Features for Domain elements, I noticed new
> features being added like
>
> <kvm>
>    <hidden state='on'/>
> </kvm>
>
> Probably more will be added later I am guessing.
>
> -Is this a performance feature?
> -Can it also be applied to qemu only machine templates? (I don't use
> qemu only, but maintain templates for both that's the reason for asking)
>

The option was introduced in d0711642 (v.1.2.8), and as the commit 
message says:

     Add new 'kvm' domain feature and ability to hide KVM signature

     QEMU 2.1 added support for the kvm=off option to the -cpu command,
     allowing the KVM hypervisor signature to be hidden from the guest.
     This enables disabling of some paravirualization features in the
     guest as well as allowing certain drivers which test for the
     hypervisor to load.  Domain XML syntax is as follows:

For non qemu drivers the option is parsed and formatted back, but 
ignored on domain startup.

Michal