libvirt users - Aug 2015 - CPU feature 'svm' not reported inside guest without 'host-passthrough'

Hi,
I am confused by the behaviour of the CPU description in my VM. I have a host
with an AMD CPU with
SVM feature and I want to try nested virtualization on a Fedora22 guest. The
host is Fedora22 as well.

libvirtd (libvirt) 1.2.13.1
kernel 4.1.6-200.fc22.x86_64

1.
I tried 'custom' mode with model qemu64 with required feature
'SVM' but '/proc/cpuinfo' in the guest
doesn't show SVM.

2.
However, if I forbid the SVM feature, the guest can't be created and libvirt
complains that the host CPU
has SVM.

3.
The only way to have SVM reported in '/proc/cpuinfo' inside the guest VM
is using 'host-passthrough'
mode, but I want to avoid it to allow migration of the VM.


Is this an issue with AMD



This is part of the description of the guest:

<domain type='kvm'>
  <name>vagrant-fedora-libvirt-nested_default</name>
  <uuid>4a379890-b891-4971-aad6-12fad45eaebc</uuid>
  <memory unit='KiB'>8388608</memory>
  <currentMemory unit='KiB'>8388608</currentMemory>
  <vcpu placement='static'>4</vcpu>
  <os>
    <type arch='x86_64'
machine='pc-i440fx-2.3'>hvm</type>
    <boot dev='hd'/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <pae/>
  </features>
  <cpu mode='custom' match='exact'>
    <model fallback='allow'>qemu64</model>
    <feature policy='require' name='svm'/>
  </cpu>


Regards,
Sladjan