[libvirt-users] CPU-Capabilties for Nested Virtualization

[Michael Beham]

Hi,

I have some questions about the CPU-Capabilities for Virtualization 
especially for Nested Virtualization like the Turtles Project.
I am trying to create a Nested Environment by following the instruction 
of: 
http://kashyapc.wordpress.com/2012/01/18/nested-virtualization-with-kvm-and-amd/ 


The bare-metal system is a Dell Server with following CPU-Flags (virsh 
capabilities)

<cpu>
<arch>x86_64</arch>
<model>Opteron_G4</model>
<vendor>AMD</vendor>
<topology sockets='1' cores='8' threads='2'/>
<feature name='nodeid_msr'/>
<feature name='wdt'/>
<feature name='skinit'/>
<feature name='ibs'/>
<feature name='osvw'/>
<feature name='cr8legacy'/>
<feature name='extapic'/>
<feature name='cmp_legacy'/>
<feature name='fxsr_opt'/>
<feature name='mmxext'/>
<feature name='osxsave'/>
<feature name='monitor'/>
<feature name='ht'/>
<feature name='vme'/>
</cpu>

After adding this Flags to the XML of my first VM, the following 
XML-Attributes are written to the file, after reopening it.


<cpu mode='custom' match='exact'>
<model fallback='allow'>Opteron_G4</model>
<vendor>AMD</vendor>
<feature policy='require' name='nodeid_msr'/>
<feature policy='require' name='wdt'/>
<feature policy='require' name='skinit'/>
<feature policy='require' name='ibs'/>
<feature policy='require' name='osvw'/>
<feature policy='require' name='cr8legacy'/>
<feature policy='require' name='extapic'/>
<feature policy='require' name='cmp_legacy'/>
<feature policy='require' name='fxsr_opt'/>
<feature policy='require' name='mmxext'/>
<feature policy='require' name='osxsave'/>
<feature policy='require' name='monitor'/>
<feature policy='require' name='ht'/>
<feature policy='require' name='vme'/>
</cpu>


The problem is, that after adding this attributes to the XML, I am not 
able to load the kvm-modules in the VM. So I?m not able to install the 
Nested VM in the VM.
But when I?m not adding the attributes to the XML and keep the XML-File 
of the VM unmodified, I?m able to load the KVM modules in the VM and I 
can install the Nested Guest.

So my first question is, what difference it makes for the Nested 
Virtualization, when I?m not adding the Attributes and keep the 
XML-Files unmodified?

And my second qestion is, what essential difference is between the qemu 
version 0.14 which was used by the instruction of Kashyap Chamarthy and 
the version 1.0 related to Nested Virtualization?

I hope you understand my problem because it is quite confusing for me 
and I?m not sure that I?m using the right techniqe for my Nested 
Environment!!

Best Regards,

Mike


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