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 -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1318830 Title: High CPU usage on windows virtual machine Status in QEMU: New Status in “qemu” package in Ubuntu: Incomplete Bug description: I got Ubuntu 14.04, with Qemu 2.0 and moved my windows VM to this new box, and made sure that what this article indicates was achieved https://www.kraxel.org/blog/2014/03/qemu-and-usb-tablet-cpu-consumtion/ I can attest that it works following the instructions, erasing the registry, etc. Unfortunately, with 4 cpus as below, I still see 60% CPU outside as shown by "Top" versus 0% CPU inside. My Kernel is 3.15.0-031500rc4-generic If some developer wants to log in and take a look, I am happy to help. The box is not in production and I take full responsibility. Until this is solved, KVM is not going to compete with Hyper-V or Vmware. Basically KVM is not suitable for the Enterprise as of yet. qemu-system-x86_64 -enable-kvm -name Production -S -machine pc- i440fx-2.0,accel=kvm,usb=off -cpu kvm64,+rdtscp,+pdpe1gb,+x2apic,+dca,+pcid,+pdcm,+xtpr,+tm2,+est,+smx,+vmx,+ds_cpl,+monitor,+dtes64,+pclmuldq,+pbe,+tm,+ht,+ss,+acpi,+ds,+vme,hv_relaxed,hv_vapic,hv_spinlocks=0xfff -m 4024 -realtime mlock=off -smp 4,sockets=1,cores=4,threads=1 -uuid e8701c5c-b542-0199-fd2a-1047df24770e -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/Production.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 -drive file=/var/lib/libvirt/images/Production.img,if=none,id=drive-virtio- disk0,format=raw -device virtio-blk- pci,scsi=off,bus=pci.0,addr=0x6,drive=drive-virtio-disk0,id=virtio- disk0,bootindex=1 -netdev tap,fd=30,id=hostnet0,vhost=on,vhostfd=31 -device virtio-net- pci,netdev=hostnet0,id=net0,mac=00:16:3a:d2:cd:ea,bus=pci.0,addr=0x3 -netdev tap,fd=35,id=hostnet1,vhost=on,vhostfd=36 -device virtio-net- pci,netdev=hostnet1,id=net1,mac=52:54:00:70:fe:54,bus=pci.0,addr=0x4 -chardev pty,id=charserial0 -device isa- serial,chardev=charserial0,id=serial0 -device usb-tablet,id=input0 -vnc 127.0.0.1:0 -device VGA,id=video0,bus=pci.0,addr=0x2 -device intel-hda,id=sound0,bus=pci.0,addr=0x5 -device hda- duplex,id=sound0-codec0,bus=sound0.0,cad=0 -device virtio-balloon- pci,id=balloon0,bus=pci.0,addr=0x7 To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1318830/+subscriptions