Re: [PATCHv4 1/8] mm: Add support for unaccepted memory

[Dave Hansen]

On 4/12/22 01:15, David Hildenbrand wrote:
> Can we simply automate this using a kthread or smth like that, which
> just traverses the free page lists and accepts pages (similar, but
> different to free page reporting)?

That's definitely doable.

The downside is that this will force premature consumption of physical
memory resources that the guest may never use.  That's a particular
problem on TDX systems since there is no way for a VMM to reclaim guest
memory short of killing the guest.

In other words, I can see a good argument either way:
1. The kernel should accept everything to avoid the perf nastiness
2. The kernel should accept only what it needs in order to reduce memory
   use

I'm kinda partial to #1 though, if I had to pick only one.

The other option might be to tie this all to DEFERRED_STRUCT_PAGE_INIT.
 Have the rule that everything that gets a 'struct page' must be
accepted.  If you want to do delayed acceptance, you do it via
DEFERRED_STRUCT_PAGE_INIT.