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

Mike Rapoport
2019-10-30T07:11:48Z

On Tue, Oct 29, 2019 at 10:12:04AM +0000, Christopher Lameter wrote:
>
>
> On Tue, 29 Oct 2019, Mike Rapoport wrote:
>
> > I've talked with Thomas yesterday and he suggested something similar:
> >
> > When the MAP_EXCLUSIVE request comes for the first time, we allocate a huge
> > page for it and then use this page as a pool of 4K pages for subsequent
> > requests. Once this huge page is full we allocate a new one and append it
> > to the pool. When all the 4K pages that comprise the huge page are freed
> > the huge page is collapsed.
>
> Or write a device driver that allows you to mmap a secure area and avoid
> all core kernel modifications?
>
> /dev/securemem or so?

A device driver will need to remove the secure area from the direct map and
then we back to square one.

> It may exist already.
>

--
Sincerely yours,
Mike.