This is WIP for a kvmclock driver with vDSO support. Although this is WIP, in light of D29531 and the discussion/activity there, I thought it would make sense to offer this draft to the same audience for review, discussion, and/or any feedback after trying it in their setups/use-cases.
This is the work referenced by https://reviews.freebsd.org/D29531#663885, plus changes for the review feedback on D29531 that were relevant here as well (specifically, @kib's commenting input and @rpokala's + @imp's copyright header input).