I have this problem also using Debian Wheezy with backported qemu-kvm-2.0.0, CPU usage for idle Windows machine ,using top to measure ,is constantly >30% (while in Windows Task Manager >5%), while Linux VM beside is working fine (CPU >5%) when idle... Here are the details about packages used and qemu-kvm process: root@bojan:~# uname -a Linux bojan 3.2.0-4-amd64 #1 SMP Debian 3.2.60-1+deb7u1 x86_64 GNU/Linux root@bojan:~# dpkg -l | egrep '(qemu|kvm|spice)' ii ipxe-qemu 1.0.0+git-20120202.f6840ba-3 all PXE boot firmware - ROM images for qemu ii libspice-client-glib-2.0-1:amd64 0.12-5 amd64 GObject for communicating with Spice servers (runtime library) ii libspice-client-gtk-2.0-1:amd64 0.12-5 amd64 GTK2 widget for SPICE clients (runtime library) ii libspice-server1:amd64 0.12.4-0nocelt2~bpo70+1 amd64 Implements the server side of the SPICE protocol ii python-spice-client-gtk 0.12-5 amd64 GTK2 widget for SPICE clients (Python binding) ii qemu-keymaps 1.1.2+dfsg-6a+deb7u3 all QEMU keyboard maps ii qemu-kvm 2.0.0+dfsg-4~bpo70+1 amd64 QEMU Full virtualization on x86 hardware (transitional package) rc qemu-system 2.0.0+dfsg-4~bpo70+1 amd64 QEMU full system emulation binaries ii qemu-system-common 2.0.0+dfsg-4~bpo70+1 amd64 QEMU full system emulation binaries (common files) ii qemu-system-x86 2.0.0+dfsg-4~bpo70+1 amd64 QEMU full system emulation binaries (x86) ii qemu-utils 2.0.0+dfsg-4~bpo70+1 amd64 QEMU utilities 115 18212 36.1 35.4 2727568 2154604 ? Sl 10:07 4:08 qemu-system-x86_64 -enable-kvm -name Win7ENTx64 -S -machine pc-i440fx-2.0,accel=kvm,usb=off -cpu SandyBridge,+erms,+smep,+fsgsbase,+rdrand,+f16c,+osxsave,+pcid,+pdcm,+xtpr,+tm2,+est,+vmx,+ds_cpl,+monitor,+dtes64,+pbe,+tm,+ht,+ss,+acpi,+ds,+vme -m 2048 -realtime mlock=off -smp 2,sockets=2,cores=1,threads=1 -uuid c1be1529-83e4-82f1-5277-d82cb0e853b4 -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/Win7ENTx64.monitor,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=localtime -no-shutdown -boot strict=on -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x7 -drive file=/var/lib/libvirt/images/Win7ENTx64.qcow2,if=none,id=drive-virtio-disk0,format=qcow2 -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x5,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 -drive file=/var/lib/libvirt/images/Microsoft_Windows_7_Enterprise_x64_SP1.ISO,if=none,id=drive-ide0-1-0,readonly=on,format=raw -device ide-cd,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0 -netdev tap,fd=25,id=hostnet0,vhost=on,vhostfd=26 -device virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:00:ac:2b:78,bus=pci.0,addr=0x3 -chardev pty,id=charserial0 -device isa-serial,chardev=charserial0,id=serial0 -chardev spicevmc,id=charchannel0,name=vdagent -device virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=com.redhat.spice.0 -device usb-tablet,id=input0 -spice port=5901,addr=127.0.0.1,disable-ticketing,seamless-migration=on -device VGA,id=video0,bus=pci.0,addr=0x2 -device intel-hda,id=sound0,bus=pci.0,addr=0x4 -device hda-duplex,id=sound0-codec0,bus=sound0.0,cad=0 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x6