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[Chris Friesen <chris.friesen@xxxxxxxxxxxxx>]

Public bug reported:

Runnng Havana, we're seeing live migration fail when attempting to
migrate from an Ivy-Bridge host to a Sandy-Bridge host.

However, we're using the default kvm guest config which has a "safe"
default virtual cpu with a subset of cpu features.  /proc/cpuinfo from
within the guest looks the same on both types of hosts.

I think the problem is that when check_can_live_migrate_destination()
calls _compare_cpu(), it's comparing the host CPUs.  Instead, I think we
should be comparing the guest CPU against the host CPU of the
destination to make sure it's compatible.  (Assuming that libvirt
considers the "qemu virtual cpu" to be compatible with the host cpu.)

** Affects: nova
     Importance: Undecided
         Status: New


** Tags: compute libvirt

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https://bugs.launchpad.net/bugs/1330744

Title:
  live migration is incorrectly comparing host cpu features

Status in OpenStack Compute (Nova):
  New

Bug description:
  Runnng Havana, we're seeing live migration fail when attempting to
  migrate from an Ivy-Bridge host to a Sandy-Bridge host.

  However, we're using the default kvm guest config which has a "safe"
  default virtual cpu with a subset of cpu features.  /proc/cpuinfo from
  within the guest looks the same on both types of hosts.

  I think the problem is that when check_can_live_migrate_destination()
  calls _compare_cpu(), it's comparing the host CPUs.  Instead, I think
  we should be comparing the guest CPU against the host CPU of the
  destination to make sure it's compatible.  (Assuming that libvirt
  considers the "qemu virtual cpu" to be compatible with the host cpu.)

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