Re: [PATCH v3 3/6] mm: introduce memfd_secret system call to create "secret" memory areas

[Mike Rapoport]

On Thu, Aug 06, 2020 at 01:27:57PM +0300, Kirill A. Shutemov wrote:
> On Tue, Aug 04, 2020 at 12:50:32PM +0300, Mike Rapoport wrote:
> > From: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> > 
> > Introduce "memfd_secret" system call with the ability to create memory
> > areas visible only in the context of the owning process and not mapped not
> > only to other processes but in the kernel page tables as well.
> > 
> > The user will create a file descriptor using the memfd_secret() system call
> > where flags supplied as a parameter to this system call will define the
> > desired protection mode for the memory associated with that file
> > descriptor. Currently there are two protection modes:
> > 
> > * exclusive - the memory area is unmapped from the kernel direct map and it
> >               is present only in the page tables of the owning mm.
> > * uncached  - the memory area is present only in the page tables of the
> >               owning mm and it is mapped there as uncached.
> 
> I'm not sure why flag for exclusive mode is needed. It has to be default.
> And if you want uncached on top of that set the flag.

Makes sense.

> What am I missing?
>
> -- 
>  Kirill A. Shutemov

-- 
Sincerely yours,
Mike.