hardware: Add TODO to remove '(un)pin_cpu_with_siblings'

With the newly introduced translation of 'hw:cpu_thread_policy' to
require or avoid the 'HW_CPU_HYPERTHREADING' trait, we no longer fake
non-SMT hosts by reserving the thread siblings of each core used by an
instance. As such, once we're in a world where all hosts have switched
to reporting PCPUs and this trait (or at least are capable of it), we
will no longer need the functionality these methods enable. Add a TODO
to remind us to remove them.

Change-Id: I22032f5a96c3ba791d3b44b83259b43349093c36
Signed-off-by: Stephen Finucane <[email protected]>

Author: stephenfin

nova/virt/hardware.py

@@ -2220,6 +2220,8 @@ def numa_usage_from_instance_numa(host_topology, instance_topology,
             if instance_cell.cpuset_reserved:
                 pinned_cpus |= instance_cell.cpuset_reserved
 
+            # TODO(stephenfin): Remove the '_with_siblings' variants when we
+            # drop support for 'vcpu_pin_set' since they will then be no-ops
             if free:
                 if (instance_cell.cpu_thread_policy ==
                         fields.CPUThreadAllocationPolicy.ISOLATE):