workaround cavium thunderx silicon erratum 27704

[dann frazier]

The arm-smmu driver doesn't allow 2 different devices (SMMU 0/1) to share a namespace. So if 2 devices are connected to same SMMU, it may lead to memory corruption.

[dann frazier (dannf)]

Though this does impact the SMMU driver in v4.4, the upstream author of the workaround tells me that it isn't possible to trigger this corruption with our v4.4, since it doesn't include the new DMA API or VFIO support. I'll therefore mark this as "won't fix" for xenial. For reference, here's a pull request for a regression-tested backport of these changes to xenial, in case we decide to pull it in later:

The following changes since commit eaf0fb36e9b286241284cbc79cf9e7772882b95e:

  irqchip/gicv3-its: numa: Enable workaround for Cavium thunderx erratum 23144 (2016-06-07 09:06:08 -0700)

are available in the git repository at:

  git://git.launchpad.net/~dannf/ubuntu/+source/linux/+git/xenial lp1590168

for you to fetch changes up to 132c0883486e69a07a86e59db5746cfba2cb731c:

  iommu/arm-smmu: Workaround for ThunderX erratum #27704 (2016-06-07 16:19:17 -0600)

----------------------------------------------------------------
Tirumalesh Chalamarla (2):
      iommu/arm-smmu: Add support for 16 bit VMID
      iommu/arm-smmu: Workaround for ThunderX erratum #27704

 Documentation/devicetree/bindings/iommu/arm,smmu.txt | 1 +
 drivers/iommu/arm-smmu.c | 60 ++++++++++++++++++++++++++++++++++++++++---------------
 2 files changed, 45 insertions(+), 16 deletions(-)

[dann frazier (dannf)]

This fix landed upstream in v4.11, so marking Fix Released.