Checklist

• IOMMU to prevent DMA ghosting

To clarify, do you mean CONFIG_INTEL_IOMMU and
CONFIG_INTEL_IOMMU_DEFAULT_ON? It would appear the former is generally
configured on the average distribution, but not the latter, requiring an
explicit kernel parameter to be supplied at boot in order to enable it.

> not clear to me that Linux distributions ship with this enabled,
> although that is a concern for ZFSOnLinux and various Linux
> distributions. I will patch Gentoo's genkernel software to add support
> for this functionality by default.

So you are going to enable CONFIG_INTEL_IOMMU_DEFAULT_ON in the default
Gentoo kernel config from now on? There was a mention of a similar feature
in FreeBSD, I'm not sure if it changed since this posting discussing it:

• FF and Chrome LTS/Business