I got a problem when using qemu 2.0.0 + libvirt 1.2.6 . It just can not define a kvm vm successfully ,  errors like this :

# virsh define 5ab4f49c-c99f-4dbd-9d7d-17a946b4c5a7.xml
error: Failed to define domain from 5ab4f49c-c99f-4dbd-9d7d-17a946b4c5a7.xml
error: unknown OS type hvm

after several tries, i found that 

Qemu2.0 /qemu-kvm1.2+ libvirt1.0.2 and lower version  is  ok
Qemu2.0 /qemu-kvm1.2+ libvirt1.0.3 and higher version is failed

I have checked system as bellows:
1 kvm,kvm_intel modules are loaded(centos 6.2 /kernel 2.6.32)
2 bios is ok for hvm
3 qemu is installed and emulator path in xml config file is correct
4 I also tried to install glusterfs-devel-3.2.7-1.el6.x86_64 and rebuild qemu , no use.

so ,why Qemu2.0 /qemu-kvm1.2+ libvirt1.0.3 and above version could not work?

vary much