Some workloads require to have hypervisor overheads to be isolated from the set of pCPUs running guest vCPUs threads. For libvirt driver we have introduced the emulator threads placements which provides an option to reserve an additional host CPU per guest to pin the emulator threads on [0]. To extend the flexibility and address use-cases where resources on hosts are limited. We are introducing 'overhead_pin_set' option on compute node. Operators will have ability to reserve host CPUs for hypervisor overhead. For case of libvirt driver we are extending the flavor property hw:emulator_threads_policy to accept 'host' value, meaning that the guests configured to use hw:emulator_threads_policy=host will have their emulator threads running on the set of pCPUs configured with 'overhead_pin_set' option. The blueprint [1] on launchpad.net, patches [2] and spec updated [3] [0] https://specs.openstack.org/openstack/nova-specs/specs/pike/implemented/libvirt-emulator-threads-policy.html [1] https://blueprints.launchpad.net/nova/+spec/overhead-pin-set [2] https://review.openstack.org/#/c/510897/ [3] https://review.openstack.org/#/c/511188/