Hi Chao,

Actually the current version allows you to delay the allocation to a
later time (e.g. page fault time) if you don't call fallocate() on the
private fd. fallocate() is necessary in previous versions because we
treat the existense in the fd as 'private' but in this version we track
private/shared info in KVM so we don't rely on that fact from memory
backstores.

Does this also mean reservation of guest physical memory with secure 
processor (both for SEV-SNP & TDX) will also happen at page fault time?

Do we plan to keep it this way?

Thanks,
Pankaj

Definitely the page will still be pinned once it's allocated, there is
no way to swap it out for example just with the current code. That kind
of support, if desirable, can be extended through MOVABLE flag and some
other callbacks to let feature-specific code to involve.