KVM and libvirt: wrong CPU type in virtual host - virtualization

Question

We us KVM and libvirt on a 6 core (12 HT cores) machine for virtualization.
Problem: wrong CPU type in virtual host.
used KVM, libvirt, kernel version:
libvirt version: 0.9.8
QEMU emulator version 1.0 (qemu-kvm-1.0), Copyright (c) 2003-2008 Fabrice Bellard
Ubuntu 12.04.1 LTS
kernel: 3.2.0-32-generic x86_64
/usr/share/libvirt/cpu_map.xml does not support more recent cpu types than Westmare.
Do I need this kind of virtualisation of the cpu at all? because of some reasons we need maximum cpu-performance in the virtual host. Will be glad to have some cores of the server's i7-3930K CPU#3.20GHz available in my virtual machines.
Maybe we do too muczh virtualization...?
my virtual host's xml looks like: where can I set the cpu -host flag?
<domain type='kvm'>
<name>myVirtualServer</name>
<uuid>2344481d-f455-455e-9558</uuid>
<description>Test-Server</description>
<memory>4194304</memory>
<currentMemory>4194304</currentMemory>
<vcpu>2</vcpu>
<cpu match='exact'>
<model>Westmere</model>
<vendor>Intel</vendor>
</cpu>
<os>
<type arch='x86_64' machine='pc-1.0'>hvm</type>
<boot dev='hd'/>
</os>
<features>
<acpi/>
<apic/>
<pae/>
</features>
$ lscpu of physical Server with 6 (12) cores with HT
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
CPU(s): 12
On-line CPU(s) list: 0-11
Thread(s) per core: 2
Core(s) per socket: 6
Socket(s): 1
NUMA node(s): 1
Vendor ID: GenuineIntel
CPU family: 6
Model: 45
Stepping: 7
CPU MHz: 1200.000
BogoMIPS: 6400.05
Virtualization: VT-x
L1d cache: 32K
L1i cache: 32K
L2 cache: 256K
L3 cache: 12288K
NUMA node0 CPU(s): 0-11
$ lscpu of virtual Server (wrong CPU type, wrong L2-Cache, wrong MHz)
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
CPU(s): 2
On-line CPU(s) list: 0,1
Thread(s) per core: 1
Core(s) per socket: 1
Socket(s): 2
NUMA node(s): 1
Vendor ID: GenuineIntel
CPU family: 6
Model: 15
Stepping: 11
CPU MHz: 3200.012
BogoMIPS: 6400.02
Virtualisation: VT-x
Hypervisor vendor: KVM
Virtualisation type: full
L1d cache: 32K
L1i cache: 32K
L2 cache: 4096K
NUMA node0 CPU(s): 0,1

Answer 1

in the client's xml
<cpu mode='custom' match='exact'>
<model fallback='allow'>core2duo</model>
<feature policy='require' name='vmx'/>
</cpu>
as an example. virsh edit then restart the guest.
EDIT. Ignore this. I've just re-read your question and you're already doing that.