On Mon, Jul 19, 2021 at 02:58:22PM +0200, Joerg Roedel wrote:

I'd like to get some movement again into the discussion around how to
implement runtime memory validation for confidential guests and wrote up
some thoughts on it.
Below are the results in form of a proposal I put together. Please let
me know your thoughts on it and whether it fits everyones requirements.

I think this proposal skips (intentionally?) something that s390 already
implemented: the secure guest deliberately allowing the hypervisor to
access certain pages for a period and then re-validating them.  I hope x86
can use the same interface as s390 for this, or if not, the interface can
be modified to be usable by all architectures.  See commit f28d43636d6f
("mm/gup/writeback: add callbacks for inaccessible pages").