Features/Cpu-host Support

CPU-Host Support

Summary

CPU-Host support allows the virtual machines to see and utilize the host's CPU flags, this enables better performance in VM's, at the price of worse portablity.

Owner

• Name: Laszlo Hornyak
• Email: <lhornyak@redhatdotcom>

Current status

• Merged
• Last updated date: 19 Dec 2012

Detailed Description

Since with host-passthrough gives the host cpu-capabilities to the VM's CPU, migration can not happen to different CPU-models. This could still be acceptable if all the hosts are all uniform in the cluster.

• engine modifications:
  • modify VmStatic, add useHostCpuFlags boolean property
    • database schema modification in tables, views and stored procedures
    • DAO modifications
  • modify the Add/Edit VM dialog, add 'use host cpu flags' checkbox - it should be enabled only when Vm is pinned to host

• vdsm modifications:
  • add hostPassthrough and hostModel as special cpu types http://gerrit.ovirt.org/9507 - merged
• rest-api:
  • Add new element cpu_mode with values custom, host_model and host_passthrough to CPU
  • example

<cpu><topology cores="1" sockets="1"/><cpu_mode>HOST_PASSTHROUGH</cpu_mode></cpu>

Label should be "Pass through host CPU". When this is set the VM should be marked as non-migratable

Benefit to oVirt

Allows the users to get better performance from their VM's through using all CPU capabilities - including the ones not handled by qemu/kvm

Dependencies / Related Features

• libvirt's CPU-model and topology

Documentation / External references

• BZ838469 - Support cpu -host for virtual machines