KVM live migration appears to hang and RHEL guest issues "soft lockup" messages

Solution Verified - Updated -


Live migration of a KVM virtual machine may hang on the source host at the time when most of the guest's memory has been transferred to the destination host. This issue has been observed with medium or large sized virtual machines, for example during migration of a RHEL5.8 guest with 12 virtual CPUs and 16 GB of memory. In this example, error messages such as the following have occurred on the guest console too and the guest appeared to be hung.

    BUG: soft lockup - CPU#2 stuck for 146s! [swapper:0]
    INFO: task kjournald:943 blocked for more than 120 seconds.


  • Red Hat Enterprise Linux 6.2 KVM host or Red Hat Enterprise Linux 6.2-based RHEV-H hypervisor
  • live migration of medium or large sized virtual machines

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