6.4.7 Migrating Large Hardware Virtualized Guest Results in CPU Soft Lock

On some hardware, such as the SUN FIRE X4170 M2 Server, migration of very large virtual machines using hardware virtualization can result in a soft lockup causing the virtual machine to become unresponsive. This lock is caused when the migration causes the virtual machine kernel to lose the clock source. Access to the console for the virtual machine shows a series of error messages similar to the following:

BUG: soft lockup - CPU#0 stuck for 315s! [kstop/0:2131]

To resolve this, the virtual machine must be restarted and the clocksource=jiffies option should be added to the HVM guest kernel command line, before rebooting the virtual machine again.


This option should only be used on HVM guest systems that have actually resulted in a CPU soft lock.