On Tue, Nov 23, 2021 at 10:06:02AM +0100, Paolo Bonzini wrote:

I think it's great that memfd hooks are usable by more than one subsystem,
OTOH it's fair that whoever needs it does the work---and VFIO does not need
it for confidential VMs, yet, so it should be fine for now to have a single
user.

I think adding a new interface to a core kernel subsystem should come
with a greater requirement to work out something generally useful and
not be overly wedded to a single use case (eg F_SEAL_GUEST)

Especially if something like 'single user' is not just a small
implementation artifact but a key design tennant of the whole eventual
solution.

Jason