From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754032AbaFWVEp (ORCPT ); Mon, 23 Jun 2014 17:04:45 -0400 Received: from mail-lb0-f180.google.com ([209.85.217.180]:39879 "EHLO mail-lb0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752821AbaFWVEn (ORCPT ); Mon, 23 Jun 2014 17:04:43 -0400 MIME-Version: 1.0 In-Reply-To: <53A88DE4.8050107@intel.com> References: <1403084656-27284-1-git-send-email-qiaowei.ren@intel.com> <1403084656-27284-3-git-send-email-qiaowei.ren@intel.com> <53A884B2.5070702@mit.edu> <53A88806.1060908@intel.com> <53A88DE4.8050107@intel.com> From: Andy Lutomirski Date: Mon, 23 Jun 2014 14:04:22 -0700 Message-ID: Subject: Re: [PATCH v6 02/10] x86, mpx: add MPX specific mmap interface To: Dave Hansen Cc: Qiaowei Ren , "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , X86 ML , "linux-kernel@vger.kernel.org" , Linux MM Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 23, 2014 at 1:28 PM, Dave Hansen wrote: > On 06/23/2014 01:06 PM, Andy Lutomirski wrote: >> Can the new vm_operation "name" be use for this? The magic "always >> written to core dumps" feature might need to be reconsidered. > > One thing I'd like to avoid is an MPX vma getting merged with a non-MPX > vma. I don't see any code to prevent two VMAs with different > vm_ops->names from getting merged. That seems like a bit of a design > oversight for ->name. Right? AFAIK there are no ->name users that don't also set ->close, for exactly that reason. I'd be okay with adding a check for ->name, too. Hmm. If MPX vmas had a real struct file attached, this would all come for free. Maybe vmas with non-default vm_ops and file != NULL should never be mergeable? > > Thinking out loud a bit... There are also some more complicated but more > performant cleanup mechanisms that I'd like to go after in the future. > Given a page, we might want to figure out if it is an MPX page or not. > I wonder if we'll ever collide with some other user of vm_ops->name. It > looks fairly narrowly used at the moment, but would this keep us from > putting these pages on, say, a tmpfs mount? Doesn't look that way at > the moment. You could always check the vm_ops pointer to see if it's MPX. One feature I've wanted: a way to have special per-process vmas that can be easily found. For example, I want to be able to efficiently find out where the vdso and vvar vmas are. I don't think this is currently supported. --Andy From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lb0-f176.google.com (mail-lb0-f176.google.com [209.85.217.176]) by kanga.kvack.org (Postfix) with ESMTP id CC80C6B0031 for ; Mon, 23 Jun 2014 17:04:44 -0400 (EDT) Received: by mail-lb0-f176.google.com with SMTP id w7so5355199lbi.35 for ; Mon, 23 Jun 2014 14:04:44 -0700 (PDT) Received: from mail-lb0-f179.google.com (mail-lb0-f179.google.com [209.85.217.179]) by mx.google.com with ESMTPS id bm6si27840472lbb.30.2014.06.23.14.04.42 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 23 Jun 2014 14:04:43 -0700 (PDT) Received: by mail-lb0-f179.google.com with SMTP id z11so5291756lbi.38 for ; Mon, 23 Jun 2014 14:04:42 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <53A88DE4.8050107@intel.com> References: <1403084656-27284-1-git-send-email-qiaowei.ren@intel.com> <1403084656-27284-3-git-send-email-qiaowei.ren@intel.com> <53A884B2.5070702@mit.edu> <53A88806.1060908@intel.com> <53A88DE4.8050107@intel.com> From: Andy Lutomirski Date: Mon, 23 Jun 2014 14:04:22 -0700 Message-ID: Subject: Re: [PATCH v6 02/10] x86, mpx: add MPX specific mmap interface Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: Qiaowei Ren , "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , X86 ML , "linux-kernel@vger.kernel.org" , Linux MM On Mon, Jun 23, 2014 at 1:28 PM, Dave Hansen wrote: > On 06/23/2014 01:06 PM, Andy Lutomirski wrote: >> Can the new vm_operation "name" be use for this? The magic "always >> written to core dumps" feature might need to be reconsidered. > > One thing I'd like to avoid is an MPX vma getting merged with a non-MPX > vma. I don't see any code to prevent two VMAs with different > vm_ops->names from getting merged. That seems like a bit of a design > oversight for ->name. Right? AFAIK there are no ->name users that don't also set ->close, for exactly that reason. I'd be okay with adding a check for ->name, too. Hmm. If MPX vmas had a real struct file attached, this would all come for free. Maybe vmas with non-default vm_ops and file != NULL should never be mergeable? > > Thinking out loud a bit... There are also some more complicated but more > performant cleanup mechanisms that I'd like to go after in the future. > Given a page, we might want to figure out if it is an MPX page or not. > I wonder if we'll ever collide with some other user of vm_ops->name. It > looks fairly narrowly used at the moment, but would this keep us from > putting these pages on, say, a tmpfs mount? Doesn't look that way at > the moment. You could always check the vm_ops pointer to see if it's MPX. One feature I've wanted: a way to have special per-process vmas that can be easily found. For example, I want to be able to efficiently find out where the vdso and vvar vmas are. I don't think this is currently supported. --Andy -- 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