[XEN/KVM] pch audio doesn't work on both Windows and linux guest with soundhw="ac97"

Environment:

when try to boot a guest by qemu with parameter "-soundhw ac97", it showed like below:
"audio: Could no init “oss” audio driver.",
then login the guest and try run audio, no sound output.
Reproduce:
1. kvm: qemu-system-x86_64 -enable-kvm -m 2048 -smp 4 -net nic,model=rtl8139 -net tap,script=/etc/kvm/qemu-ifup -soundhw ac97 -hda [target.img]
   xen: add the audio device in guest configure file by soundhw="ac97", xl create $guest-configure
2. it will show "audio: Could no init “oss” audio driver".
3. login in guest, it can detect audio device, but actually it is not working.