It turns out, that if you use the ACPI Multiprocessor, this problem goes away. If you use MPS Multiprocessor, then this problem occurs. The worst part is if you originally built the VM without ACPI, then there is *no way* to use on the ACPI HALs in Windows XP without reinstalling. There's a ton of MS knowledge base articles about this.
-- 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: New 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
