[vfio-users] PSA: Disable transparent huge pages on v4.5+

[Alex Williamson]

Public service announcement: Changes that went in for the v4.5 kernel seems
to be disrupting page pinning for vfio.  This potentially means that VM
pages could change out from under the IOMMU mapping resulting in incorrect
DMA operations.  Since v4.5 kernels are now starting to trickle into stable
distribution releases, I would encourage transparent huge pages be disabled
in those kernels for the time being.  This can easily be done by adding the
kernel boot parameter 'transparent_hugepage=never'.  Use of hugetlbfs for
VM memory would likely also avoid this issue.  I expect we'll have a fix
soon, which will be backported to v4.5 via stable.  Thanks,

Alex
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