Re: [PATCH RFC] mm: add MAP_EXCLUSIVE to create exclusive user mappings

On Mon, 28 Oct 2019, Kirill A. Shutemov wrote:

Setting a single 4k page non-present in the direct mapping will require
splitting 2M or 1G page we usually map direct mapping with. And it's one
way road. We don't have any mechanism to map the memory with huge page
again after the application has freed the page.

It might be okay if all these pages cluster together, but I don't think we
have a way to achieve it easily.

Set aside a special physical memory range for this and migrate the
page to that physical memory range when MAP_EXCLUSIVE is specified?

Maybe some processors also have hardware ranges that offer additional
protection for stuff like that?