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.
SUSE Linux Enterprise Server 15 Service Pack 1 (SLES 15 SP1)
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.
- 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
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.
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- Document ID:7024182
- Creation Date:
- Modified Date:03-Mar-2020
- SUSE Linux Enterprise Server
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