Comment 5 for bug 1011848

Reviewed: https://review.openstack.org/8422
Committed: http://github.com/openstack/nova/commit/3114a97ba188895daff4a3d337b2c73855d4632d
Submitter: Jenkins
Branch: master

commit 3114a97ba188895daff4a3d337b2c73855d4632d
Author: Daniel P. Berrange <email address hidden>
Date: Mon Jun 11 17:16:10 2012 +0100

    Update default policies for KVM guest PIT & RTC timers

    The default policies for the KVM guest PIT and RTC timers
    are not very good at maintaining reliable time in guest
    operating systems. In particular Windows 7 guests will
    often crash with the default KVM timer policies, and old
    Linux guests will have very bad time drift

    Set the PIT such that missed ticks are injected at the
    normal rate, ie they are delayed

    Set the RTC such that missed ticks are injected at a
    higher rate to "catch up"

    This corresponds to the following libvirt XML

      <clock offset='utc'>
        <timer name='pit' tickpolicy='delay'/>
        <timer name='rtc' tickpolicy='catchup'/>
      </clock>

    And the following KVM options

      -no-kvm-pit-reinjection
      -rtc base=utc,driftfix=slew

    This should provide a default configuration that works
    acceptably for most OS types. In the future this will
    likely need to be made configurable per-guest OS type.

    Fixes LP bug #1011848

    Change-Id: Iafb0e2192b5f3c05b6395ffdfa14f86a98ce3d1f
    Signed-off-by: Daniel P. Berrange <email address hidden>