megaraid_sas Fails to Enumerate VDs When mem_encrypt=on in DELL EMC AMD Based Servers

This document (7024182) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 15 Service Pack 1 (SLES 15 SP1)

Situation

This issue affects DELL EMC AMD based Servers with a H330 (or any PERC9) storage controller with VDs created underneath it. When booting to SLES 15 SP1 GM installer iso with mem_encrypt=on kernel boot parameter, no VDs are listed by the installer. OS logs indicate that the megaraid_sas driver has failed to allocate DMA buffers hence no VDs are exposed.

Resolution

- Workaround: Set kernel boot parameters "iommu=nopt iommu.passthrough=0" to disable iommu passthrough. These parameters are required as a work around for the old kernel.
 
- Permanent fix: Update kernel to kernel-default-4.12.14-197.18.1 or later. The kernel fix is accepted upstream and details can be found at https://lkml.org/lkml/2019/8/19/459.

Cause

SME with passthrough mode is fragile with devices requiring SWIOTLB, mainly because SWIOTLB has a maximum allocation size of 256kb and a limit overall size of the bounce buffer. 

 Therefore having IOMMU in translation mode by default is better when SME is active on a system. 

 Hence now as a resolution it disables IOMMU Passthrough mode when SME is active even when CONFIG_IOMMU_DEFAULT_PASSTHROUGH=y is set.

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:7024182
  • Creation Date: 15-Oct-2019
  • Modified Date:03-Mar-2020
    • SUSE Linux Enterprise Server

< Back to Support Search

For questions or concerns with the SUSE Knowledgebase please contact: tidfeedback@suse.com

SUSE Support Forums

Get your questions answered by experienced Sys Ops or interact with other SUSE community experts.

Join Our Community

Support Resources

Learn how to get the most from the technical support you receive with your SUSE Subscription, Premium Support, Academic Program, or Partner Program.


SUSE Customer Support Quick Reference Guide SUSE Technical Support Handbook Update Advisories
Support FAQ

Open an Incident

Open an incident with SUSE Technical Support, manage your subscriptions, download patches, or manage user access.

Go to Customer Center