Xen fails to boot or hangs

This document (3692489) is provided subject to the disclaimer at the end of this document.

Environment

Novell SUSE Linux Enterprise Server 10
Xen virtualisation

Dual-core system with less than 2 GB of memory, or
Quad-core system with less than 4 GB of memory

Situation

System is stable when not using Xen, but when booting with Xen, the system hangs during the boot process or when running I/O-intensive workloads.

This behaviour may also involve error messages similar to the following:
ERROR: PCI-DMA: Out of SW-IOMMU space for 16384 bytes at device 0000:06:01.0
ERROR: Kernel panic - not syncing: PCI-DMA: Memory would be corrupted
ERROR: Kernel panic - not syncing: PCI-DMA: Random memory would be DMAed
but can also occur without error messages.

Resolution

Update to kernel-xen-2.6.16.60-0.25 or newer. If the problem persists, please contact Novell Technical Services.

Additional Information

Troubleshooting hints

The error messages listed above do not always show up on the system console and may require a serial console setup to be seen. Refer to TID 3456486: Configuring a Remote Serial Console for SLES for setup details.

Workaround for older kernels

Add the parameter
swiotlb=16
to the kernel command line of the Dom0 Linux kernel. This causes the kernel to reserve additional memory for the swiotlb. If the problem remains reproducible, change the parameter to a larger power of 2, e.g.
swiotlb=64

Background


The swiotlb is a software implementation of a translation lookaside buffer (TLB) for input/output (I/O). Many systems implement I/O TLBs in hardware (sometimes known as "DMA address translation hardware"), but this hardware implementation is often not usable for virtualisation; refer to the Wikipedia article IOMMU for background.

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:3692489
  • Creation Date: 04-Jun-2007
  • Modified Date:03-Mar-2020
    • SUSE Linux Enterprise Server

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