Xen fails to boot or hangs
This document (3692489) is provided subject to the disclaimer at the end of this document.
Environment
SUSE Linux Enterprise Server 10
Situation
Dual-core system with less than 2 GB of memory, or
Quad-core system with less than 4 GB of memory
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.
Quad-core system with less than 4 GB of memory
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 SUSE 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=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.
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:14-Mar-2021
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- SUSE Linux Enterprise Server
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