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[Brad Figg <brad.figg@xxxxxxxxxxxxx>]

This bug is missing log files that will aid in diagnosing the problem.
>From a terminal window please run:

apport-collect 1567159

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable
to run this command, please add a comment stating that fact and change
the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the
Ubuntu Kernel Team.

** Changed in: linux (Ubuntu)
       Status: New => Incomplete

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https://bugs.launchpad.net/bugs/1567159

Title:
  Ubuntu 15.10: After hot plug vcpu, kvm_arch->use_master_clock will
  never be true.

Status in linux package in Ubuntu:
  Incomplete

Bug description:
  1. In function kvm_write_tsc, when tsc first matched, do
  kvm->arch.nr_vcpus_matched_tsc++;

  2. In function pvclock_update_vm_gtod_copy, if vcpus_matched (also
  with other conditions meet), ka->use_master_clock will be true;

  3. After hot plug vcpu, kvm_arch_vcpu_postcreate and Qemu will call
  kvm_write_tsc for the new vcpu. Because the tsc will not match, so do
  kvm->arch.nr_vcpus_matched_tsc = 0;

  4. For other already existed vcpu will not call kvm_write_tsc, so will
  not do kvm->arch.nr_vcpus_matched_tsc++;

  5. So vcpus_matched in function pvclock_update_vm_gtod_copy will be
  false forever, this cause ka->use_master_clock will never be true;

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