Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965241AbdCXJAq (ORCPT ); Fri, 24 Mar 2017 05:00:46 -0400 Received: from mail-wm0-f65.google.com ([74.125.82.65]:36095 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964786AbdCXJAk (ORCPT ); Fri, 24 Mar 2017 05:00:40 -0400 Date: Fri, 24 Mar 2017 11:59:31 +0300 From: "Kirill A. Shutemov" To: hpa@zytor.com Cc: "Aneesh Kumar K.V" , linux-arch , Thomas Gleixner , Ingo Molnar , Michal Hocko , linux-kernel@vger.kernel.org, Andrew Morton , "Kirill A. Shutemov" , Arnd Bergmann , Andy Lutomirski , Dave Hansen , linux-mm@kvack.org, x86@kernel.org, Andi Kleen , Linus Torvalds Subject: Re: [PATCH 26/26] x86/mm: allow to have userspace mappings above 47-bits Message-ID: <20170324085931.7hvhrs2emqu5k5mr@node.shutemov.name> References: <20170313055020.69655-1-kirill.shutemov@linux.intel.com> <20170313055020.69655-27-kirill.shutemov@linux.intel.com> <87a88jg571.fsf@skywalker.in.ibm.com> <20170317175714.3bvpdylaaudf4ig2@node.shutemov.name> <877f3lfzdo.fsf@skywalker.in.ibm.com> <95631D05-2CA2-4967-A29E-DB396C76F62D@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <95631D05-2CA2-4967-A29E-DB396C76F62D@zytor.com> User-Agent: NeoMutt/20170306 (1.8.0) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 587 Lines: 16 On Mon, Mar 20, 2017 at 11:08:41AM -0700, hpa@zytor.com wrote: > 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 had the same argument (on your side) before, but if you look on numbers it's far from the middle of address space. The barrier is around 0.2% from the start 56-bit address space. And it's we have vdso/vvar/stack just below the barier anyway. I don't think we would loose much if wouldn't not allow VMA to sit across it. -- Kirill A. Shutemov