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Date: Mon, 20 Mar 2017 11:38:54 -0700
From: Matthew Wilcox <willy@infradead.org>
To: hpa@zytor.com
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
        linux-arch <linux-arch@vger.kernel.org>,
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        Andrew Morton <akpm@linux-foundation.org>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
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        Dave Hansen <dave.hansen@intel.com>, linux-mm@kvack.org,
        x86@kernel.org, Andi Kleen <ak@linux.intel.com>,
        Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH 26/26] x86/mm: allow to have userspace mappings above
 47-bits
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On Mon, Mar 20, 2017 at 11:08:41AM -0700, hpa@zytor.com wrote:
> On March 19, 2017 1:26:58 AM PDT, "Kirill A. Shutemov" <kirill@shutemov.name> wrote:
> >On Mar 19, 2017 09:25, "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> 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.