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

Christopher Lameter
2019-10-29T07:08:45Z

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?