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

Jayme Howard g.prime at gmail.com
Fri Apr 29 11:32:14 UTC 2016

Are there any visible symptoms that occur when this happens?  I've been
running 4.5.0 since the week it released and haven't run into any
unexpected issues (NVIDIA virtualization checks occasionally bite me, but I
consider that expected).  Just trying to determine if it's worth fixing
what doesn't appear to be broken currently.

On Thu, Apr 28, 2016 at 7:39 PM, Alex Williamson <
alex.l.williamson at gmail.com> wrote:

> 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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