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[Serge Hallyn <1567167@xxxxxxxxxxxxxxxxxx>]

Thanks for reporting this bug.  The 'kvm' package shouldn't really
exist.  The bug you're referring to is in the kernel kvm code, so I'm
marking it as affecting the kernel.  (If it were in the userspace qemu
package, then the 'qemu' package would be the right bug target).

** Package changed: kvm (Ubuntu) => linux (Ubuntu)

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https://bugs.launchpad.net/bugs/1567167

Title:
  Ubuntu 15.10: tsc_offset is error for hot-plugged vcpu.

Status in linux package in Ubuntu:
  New

Bug description:
  1. when hot plug vcpu, KVM will call kvm_write_tsc set the new vcpu's
  tsc_offset to host tsc.  The new vcpu's tsc_offsets is greatly
  different from preallocated vcpu's tsc_offset.

  2. For redhat 6.x, the vm will show warning and turn off TSC clock.
  kernel: CPU 1 got hotplugged
  kernel: kvm-clock: cpu 1, msr 0:282367c1, secondary cpu clock
  kernel: TSC synchronization [CPU#0 -> CPU#1]:
  kernel: Measured 150076598781 cycles TSC warp between CPUs, turning off TSC clock.
  kernel: Marking TSC unstable due to check_tsc_sync_source failed

  3. I think should set the new vcpu's tsc_offset to
  kvm->arch.cur_tsc_offset.

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