How to find the actually schedulable CPUs in a Linux + cgroups setup?

Hi, Right now, looking at the QEMU driver, libvirt supports listing all of the present CPUs on the hypervisor via /sys/devices/system/cpu/present. For systems where cgroups with exclusive CPU bits are configured, however, there might be CPUs that are not availabe to libvirt. This leads to situations where a domain cannot be started because of an invalid cpuset attribute (using a CPU with an exclusive bit set). My initial idea was to refactor functions like virNodeGetCPUMap() to take into account cgroup limits. danpb mentioned in #virt (thanks danpb!) that libvirtd might run in a cgroup that is not the one in which VMs will run (like on systemd hosts where libvirtd will run under /sys/fs/cgroup/system.slice/, and VMs under /sys/cgroup/machine.slice/), so just reading hardcoded cgroup files is not a good idea. Is it possible for libvirt to figure out what the actually schedulable CPUs are? Ideally users can then query this information via `virsh nodeinfo` or `virsh capabilities`. --- Regards, Biser