I've got a libvirt-created instance where I've been messing with affinity, and now something is strange. I did the following in python: ([(0, 1, 528150000000L, 2), (1, 1, 548070000000L, 3)], [(False, False, True, False), (False, False, True, False)]) I'm totally confused by that "3". It's supposed to represent the physical cpu that virtual cpu 1 is running on. But cpu 3 isn't even in the allowable affinity map for vcpu 1. If I query the data other ways, I get both cpus running on physical cpu 2: root@compute-0:~# virsh vcpupin instance-00000027 VCPU: CPU Affinity ---------------------------------- 0: 2 1: 2 root@compute-0:~# virsh emulatorpin instance-00000027 emulator: CPU Affinity ---------------------------------- *: 2 root@compute-0:~# taskset -pac 15072 pid 15072's current affinity list: 2 pid 15073's current affinity list: 1-3 pid 15075's current affinity list: 2 pid 15076's current affinity list: 0 So I'm left with the conclusion that there is something strange going on with libvirt-python. Anyone got any ideas? Chris