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Fixed

LIN5-18026 : WRL5: Fix with DMA when using WR-kernel as Crash-kernel

Created: Feb 14, 2014    Updated: Dec 19, 2017
Resolved Date: Mar 16, 2014
Found In Version: 5.0.1.10
Fix Version: 5.0.1.13
Severity: Standard
Applicable for: Wind River Linux 5
Component/s: Kernel

Description

When using the wr-kernel as a crashkernel on the hp-blades (bl 460c)
at Customer there is a problem when the iommu is used. When the
crashkernel boots up it almost always freezes. Sometimes I also see
some IOCHK nmi:s.

The reason for this is that device DMA transactions is still going on
from the previous kernel. When the crashkernel boots up, it tampers
with the iommu and this raises havoc when those DMA transactions are
running.

This problem has been discussed for a long time in the community and
there is a patchset that is being worked on. I resolved this problem
by applying one upstream patch along with the patchset mentioned. They
are now in wrl-ecs but I think engineering should consider them for
the product since it is a general problem for cpus with the
intel-iommu (vt-d).

Workaround

This is a link to the upstream patch:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/drivers/iommu/intel-iommu.c?id=3a93c841c2b3b14824f7728dd74bd00a1cedb806

This is the link to the lkml pathset discussion:
https://lkml.org/lkml/2014/1/10/518

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