From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753866AbaA1GmI (ORCPT ); Tue, 28 Jan 2014 01:42:08 -0500 Received: from mail-ea0-f182.google.com ([209.85.215.182]:53663 "EHLO mail-ea0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750816AbaA1GmG (ORCPT ); Tue, 28 Jan 2014 01:42:06 -0500 Date: Tue, 28 Jan 2014 07:42:02 +0100 From: Ingo Molnar To: Ren Qiaowei Cc: "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , x86@kernel.org, linux-kernel@vger.kernel.org, Peter Zijlstra Subject: Re: [PATCH v3 0/4] Intel MPX support Message-ID: <20140128064202.GA20869@gmail.com> References: <1390727338-20487-1-git-send-email-qiaowei.ren@intel.com> <20140126081912.GA28831@gmail.com> <52E4C551.7020402@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <52E4C551.7020402@intel.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Ren Qiaowei wrote: > >> MPX kernel code, namely this patchset, has mainly the 2 > >> responsibilities: provide handlers for bounds faults (#BR), and > >> manage bounds memory. > > > > AFAICS the kernel side implementation causes no runtime overhead > > for non-MPX workloads, and also causes no runtime overhead for > > non-MPX hardware, right? > > Yes. Actually, I think that's not entirely true. For example if within the same mm there's a lot of non-MPX threads and an MPX thread, then the MMU notifier will be called for MMU operations of every non-MPX thread as well! So MPX state of a thread will slow down all the other non-MPX threads as well. The statement is only true for non-MPX tasks that have their separate mm's that does not have a single MPX thread. Thanks, Ingo