WinXP chews 200% CPU when switched in device manager to "MPS computer" from "ACPI computer" even if there's no -no-acpi on the kvm command line (after some tries I was able to switch it from ACPI to MPS). So it is how windows works, not how kvm works.
** Changed in: qemu Status: New => Invalid -- Windows XP uses 200% CPU when given 2 VCPUs https://bugs.launchpad.net/bugs/654913 You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. Status in QEMU: Invalid Bug description: When using libvirt to give a domain 2 CPUs (<domain type='kvm'><vcpu>2</vcpu></domain>), the Windows XP kvm process will use 200% CPU when Windows is idle. Switching the number of CPUs back to 1, the kvm process gives normal idle percentages. Using libvirt 0.8.3-1ubuntu9, tried with the following qemu-kvm packages: qemu-kvm_0.12.4+noroms-0ubuntu7_amd64.deb qemu-kvm_0.12.5+noroms-0ubuntu4_amd64.deb The smp flag being set by libvirt is: -smp 2,sockets=2,cores=1,threads=1