..., getting in the way of, in particular, PVH Dom0 accessing its video
frame buffer (if it has a console).

While especially the 1st one may not appear to be so, both of the earlier
patches are strictly prereqs to the last one.

1: correct special page checking in epte_get_entry_emt()
2: avoid marking non-present entries for re-configuring
3: drop questionable mfn_valid() from epte_get_entry_emt()

Jan