ちゃんと動いている設定はこれです。
LC_ALL=C PATH=/usr/local/sbin:/usr/local/bin:/usr/bin:/usr/sbin:/sbin:/bin QEMU_AUDIO_DRV=spice /usr/bin/kvm-spice
-name win7
-S -machine pc-i440fx-utopic,accel=kvm,usb=off
-cpu SandyBridge
-m 4096
-realtime mlock=off
-smp 2,sockets=2,cores=1,threads=1
-uuid c2c9920e-0102-4c5c-b5bc-02944d185d0f
-no-user-config
-nodefaults
-chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/win7.monitor,server,nowait
-mon chardev=charmonitor,id=monitor,mode=control
-rtc base=localtime,driftfix=slew
-global kvm-pit.lost_tick_policy=discard
-no-hpet
-no-shutdown
-global PIIX4_PM.disable_s3=1
-global PIIX4_PM.disable_s4=1
-boot strict=on
-device ich9-usb-ehci1,id=usb,bus=pci.0,addr=0x5.0x7
-device ich9-usb-uhci1,masterbus=usb.0,firstport=0,bus=pci.0,multifunction=on,addr=0x5
-device ich9-usb-uhci2,masterbus=usb.0,firstport=2,bus=pci.0,addr=0x5.0x1
-device ich9-usb-uhci3,masterbus=usb.0,firstport=4,bus=pci.0,addr=0x5.0x2
-device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x6
-drive file=/var/lib/libvirt/images/win7-x64-202.qcow2,if=none,id=drive-ide0-0-0,format=qcow2