I've "ported" an old VMware VM containing Windows NT 4 SP6 into libvirt/kvm/qemu and got it running (more or less). However, the CPU graph next to the VM in virt-manager shows it starts using 100% of the allocated CPU as soon as it reaches the "OS Loader" screen, and stays there even after Windows has booted and I've logged in. (There's a dip now and then, apparently when something other than idling happens!) Windows NT Task Manager shows the CPU usage at 0%. I've tried with and without ACPI, and with different CPU settings (none/default, qemu32, pentium). No difference. Host is running Fedora 16 x86_64 with the latest updates: gpxe-roms-qemu-1.0.1-4.fc16.noarch qemu-kvm-0.15.1-3.fc16.x86_64 qemu-system-x86-0.15.1-3.fc16.x86_64 qemu-common-0.15.1-3.fc16.x86_64 qemu-img-0.15.1-3.fc16.x86_64 libvirt-0.9.6-4.fc16.x86_64 libvirt-client-0.9.6-4.fc16.x86_64 libvirt-python-0.9.6-4.fc16.x86_64 virt-manager-common-0.9.0-7.fc16.noarch virt-manager-0.9.0-7.fc16.noarch No other VM (Linux or Windows) behaves this way. I thought NT was deemed to be "well behaved" (e.g., uses HLT instruction), so I'm wondering if this is normal. ps shows (except for bits I've hidden): /usr/bin/qemu-kvm -S -M pc-0.14 -cpu qemu32 -enable-kvm -m 384 -smp 1,sockets=1,cores=1,threads=1 -name BPrjwtest -uuid <hidden> -nodefconfig -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/BPrjwtest.monitor,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=localtime -device lsi,id=scsi0,bus=pci.0,addr=0x6 -drive file=/home/libvirt/images/BPrjwtest.img,if=none,id=drive-ide0-0-0,format=raw -device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0,bootindex=1 -drive file=<hidden>,if=none,media=cdrom,id=drive-ide0-1-0,readonly=on,format=raw -device ide-drive,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0,bootindex=2 -netdev tap,fd=30,id=hostnet0 -device ne2k_pci,netdev=hostnet0,id=net0,mac=<hidden>,bus=pci.0,addr=0x4 -chardev pty,id=charserial0 -device isa-serial,chardev=charserial0,id=serial0 -usb -device usb-tablet,id=input0 -vnc 127.0.0.1:3 -vga vmware -device AC97,id=sound0,bus=pci.0,addr=0x5 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3