Serial console synchronization problem and/or hanging (re)boot on full-virtual VMs

This document (7003721) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 11
SUSE Linux Enterprise Server 10 Service Pack 2
SUSE Linux Enterprise Server 10 Service Pack 3

Situation

In some cases the shutdown or boot of a fully virtualized (FV) virtual machine (VM) may hang until input is generated on the serial console.

Another - more common - problem is that the input and output on the serial console gets out of synchronization, so that the last input character (or output line/character) does not get displayed until some key gets pressed.
An example of this would be that if the characters "Hello" gets typed, then the console will only display "Hell" until another key is pressed.

Furthermore the problem only seems to exhibit when multiple VCPUs are allocated to the VM. The more VCPUs, the easier to trigger the problem. It has not been possible to reproduce on uniprocessor VMs.

It does not matter if the VM host is running SLES 10 SP2, SLES 10 SP3 or SLES 11. Both SLES 10 and SLES 11 VMs experience the problem.

Resolution

This is a bug in the linux kernel and a patch has been produced and verified to fix the problem.
The patch is included in the following kernels for the respective products :
SLES 10 SP2 : 2.6.16.60-0.42.8
SLES 10 SP3 : 2.6.16.60-0.59.1
SLES 11 : 2.6.27.42-0.1.1


Additional Information

For information about configuring serial console on fully virtualized VMs, see How to configure serial console access on full virtual SLE VM

Disclaimer

This Support Knowledgebase provides a valuable tool for SUSE customers and parties interested in our products and solutions to acquire information, ideas and learn from one another. Materials are provided for informational, personal or non-commercial use within your organization and are presented "AS IS" WITHOUT WARRANTY OF ANY KIND.

  • Document ID:7003721
  • Creation Date: 01-Jul-2009
  • Modified Date:03-Mar-2020
    • SUSE Linux Enterprise Server

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