QEMU does not support Westmere (Intel Xeon) CPU model Setting the CPU model to Westmere (Intel Xeon server CPU) is not possible. libvirt uses 'core2duo' as fallback: https://bugzilla.redhat.com/show_bug.cgi?id=708927 $ qemu -cpu ? x86 [n270] x86 [athlon] x86 [pentium3] x86 [pentium2] x86 [pentium] x86 [486] x86 [coreduo] x86 [kvm32] x86 [qemu32] x86 [kvm64] x86 [core2duo] x86 [phenom] x86 [qemu64] $ qemu --version QEMU emulator version 1.0 (Debian 1.0+dfsg-3), Copyright (c) 2003-2008 Fabrice Bellard An application test with high cpu load gives the timing statistics give: bare metal virtual percent X4560 cpu 50m28s 54m0s 107% X5690 (westermere) 29m20s 38m0s 134% Westmere seems to be available in the latest version of QEMU: $ qemu-system-x86_64 -cpu ? | grep Westmere x86 Westmere Westmere E56xx/L56xx/X56xx (Nehalem-C) ==> Setting status to "Fix released" now.