When the default cpuset or automatic numa placement is used libvirt
would place the whole parent cgroup in the specified cpuset. This then
disallowed to re-pin the vcpus to a different cpu.
This patch pins only the vcpu threads to the default cpuset and thus
allows to re-pin them later.
The following config would fail to start:
<domain type='kvm'>
...
<vcpu placement='static' cpuset='0-1' current='2'>4</vcpu>
<cputune>
<vcpupin vcpu='0' cpuset='2-3'/>
...
This is a regression since a39f69d2b.
f0fa9080d4