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authorSergio Gonzalez Monroy <sergio.gonzalez.monroy@intel.com>2014-12-15 10:32:43 +0000
committerThomas Monjalon <thomas.monjalon@6wind.com>2014-12-20 00:38:39 +0100
commit7547be1efc1e19558b489be5dc79822b23bd2a36 (patch)
tree6808ed1b694a43a73624b93a2bb39b64a37ed875
parent048f830326227cf05d9ef6e4899764d10cc86970 (diff)
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doc: add known issue for iommu and igb_uio
Known issue regarding iommu/VT-d and igb_uio in Linux kernel version 3.15 to 3.17 where unbinding the device from the driver removes the 1:1 mapping in the iommu resulting in IOMMU/DMAR errors when the device tries to access memory. Signed-off-by: Sergio Gonzalez Monroy <sergio.gonzalez.monroy@intel.com> Acked-by: Bernard Iremonger <bernard.iremonger@intel.com>
-rw-r--r--doc/guides/rel_notes/known_issues.rst32
1 files changed, 32 insertions, 0 deletions
diff --git a/doc/guides/rel_notes/known_issues.rst b/doc/guides/rel_notes/known_issues.rst
index 12a1876..6c81fcf 100644
--- a/doc/guides/rel_notes/known_issues.rst
+++ b/doc/guides/rel_notes/known_issues.rst
@@ -777,3 +777,35 @@ Stopping the port does not down the link on IntelĀ® 40G ethernet controller
| Driver/Module | Poll Mode Driver (PMD) |
| | |
+--------------------------------+--------------------------------------------------------------------------------------+
+
+Devices bound to igb_uio with VT-d enabled do not work on Linux* kernel 3.15-3.17
+---------------------------------------------------------------------------------
+
++--------------------------------+--------------------------------------------------------------------------------------+
+| Title | Devices bound to igb_uio with VT-d enabled do not work on Linux* kernel 3.15-3.17 |
++================================+======================================================================================+
+| Description | | When VT-d is enabled (iommu=pt intel_iommu=on), devices are 1:1 mapped. |
+| | In the Linux* kernel unbinding devices from drivers removes that mapping which |
+| | result in IOMMU errors. |
+| | | Introduced in Linux `kernel 3.15 commit <https://git.kernel.org/cgit/linux/kernel/ |
+| | git/torvalds/linux.git/commit/drivers/iommu/ |
+| | intel-iommu.c?id=816997d03bca9fabcee65f3481eb0297103eceb7>`_, |
+| | solved in Linux `kernel 3.18 commit <https://git.kernel.org/cgit/linux/kernel/git/ |
+| | torvalds/linux.git/commit/drivers/iommu/ |
+| | intel-iommu.c?id=1196c2fb0407683c2df92d3d09f9144d42830894>`_. |
++--------------------------------+--------------------------------------------------------------------------------------+
+| Implication | | Devices will not be allowed to access memory, resulting in following kernel errors:|
+| | | ``dmar: DRHD: handling fault status reg 2`` |
+| | | ``dmar: DMAR:[DMA Read] Request device [02:00.0] fault addr a0c58000`` |
+| | | ``DMAR:[fault reason 02] Present bit in context entry is clear`` |
++--------------------------------+--------------------------------------------------------------------------------------+
+| Resolution/ Workaround | | Use earlier or later kernel versions, or avoid driver binding on boot by |
+| | blacklisting the driver modules. |
+| | | ie. in the case of ixgbe, we can pass the kernel command line option: |
+| | | ``modprobe.blacklist=ixgbe`` |
+| | | This way we do not need to unbind the device to bind it to igb_uio. |
++--------------------------------+--------------------------------------------------------------------------------------+
+| Affected Environment/ Platform | Linux* systems with kernel versions 3.15 to 3.17 |
++--------------------------------+--------------------------------------------------------------------------------------+
+| Driver/Module | igb_uio module |
++--------------------------------+--------------------------------------------------------------------------------------+