Re: [PATCH 26/26] x86/mm: allow to have userspace mappings above 47-bits

[Matthew Wilcox]

On Mon, Mar 20, 2017 at 11:08:41AM -0700, hpa@xxxxxxxxx wrote:
> On March 19, 2017 1:26:58 AM PDT, "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx> wrote:
> >On Mar 19, 2017 09:25, "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx> wrote:
> > > What is the epectation when the hint addr is below 128TB but addr + len
> > > 128TB ? Should such mmap request fail ?
> >
> >Yes, I believe so.
> 
> This *better* be conditional on some kind of settable limit.  Having a
> barrier in the middle of the address space for no apparent reason to
> "clean" software is insane.

I disagree with Kirill here.  If addr+len > 128TB, I think we should
assume the application is 57-bit aware.

Specifying hint addresses is such a rare thing to do anyway.