From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f200.google.com (mail-pf0-f200.google.com [209.85.192.200]) by kanga.kvack.org (Postfix) with ESMTP id 8C8EF6B0005 for ; Wed, 22 Jun 2016 15:56:57 -0400 (EDT) Received: by mail-pf0-f200.google.com with SMTP id e189so126112092pfa.2 for ; Wed, 22 Jun 2016 12:56:57 -0700 (PDT) Received: from mga03.intel.com (mga03.intel.com. [134.134.136.65]) by mx.google.com with ESMTP id h24si1515152pfk.146.2016.06.22.12.56.56 for ; Wed, 22 Jun 2016 12:56:56 -0700 (PDT) Subject: Re: JITs and 52-bit VA References: <4A8E6E6D-6CF7-4964-A62E-467AE287D415@linaro.org> <576AA67E.50009@codeaurora.org> <20160622191843.GA2045@uranus.lan> From: Dave Hansen Message-ID: <576AED88.6040805@intel.com> Date: Wed, 22 Jun 2016 12:56:56 -0700 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Andy Lutomirski , Cyrill Gorcunov Cc: Christopher Covington , Maxim Kuvyrkov , Linaro Dev Mailman List , Arnd Bergmann , Mark Brown , "linux-mm@kvack.org" , Dmitry Safonov On 06/22/2016 12:20 PM, Andy Lutomirski wrote: >>> >> As an example, a 32-bit x86 program really could have something mapped >>> >> above the 32-bit boundary. It just wouldn't be useful, but the kernel >>> >> should still understand that it's *user* memory. >>> >> >>> >> So you'd have PR_SET_MMAP_LIMIT and PR_GET_MMAP_LIMIT or similar instead. >> > >> > +1. Also it might be (not sure though, just guessing) suitable to do such >> > thing via memory cgroup controller, instead of carrying this limit per >> > each process (or task structure/vma or mm). > I think we'll want this per mm. After all, a high-VA-limit-aware bash > should be able run high-VA-unaware programs without fiddling with > cgroups. Yeah, cgroups don't make a lot of sense. On x86, the 48-bit virtual address is even hard-coded in the ABI[1]. So we can't change *any* program's layout without either breaking the ABI or having it opt in. But, we're also lucky to only have one VA layout since day one. 1. www.x86-64.org/documentation/abi.pdf - a??... Therefore, conforming processes may only use addresses from 0x00000000 00000000 to 0x00007fff ffffffff .a?? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org