From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030867AbaLLQkr (ORCPT ); Fri, 12 Dec 2014 11:40:47 -0500 Received: from terminus.zytor.com ([198.137.202.10]:47892 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030331AbaLLQkq (ORCPT ); Fri, 12 Dec 2014 11:40:46 -0500 Message-ID: <548B1A7D.7040403@zytor.com> Date: Fri, 12 Dec 2014 08:40:29 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: Linus Torvalds , Dave Hansen CC: Thomas Gleixner , LKML , Andrew Morton , the arch/x86 maintainers Subject: Re: [GIT pull] x86 mpx support for 3.19 References: <5488A203.7000600@linux.intel.com> <5488AF8D.5070702@linux.intel.com> In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/10/2014 12:49 PM, Linus Torvalds wrote: > On Wed, Dec 10, 2014 at 12:39 PM, Dave Hansen > wrote: >> >> I misspoke there. I meant SMAP (I placed MPX below its config option). > > Ok, I agree on SMAP, we might want to have that be configurable too, > especially for smaller systems (I *think* SMAP is big-core only, > right?). I'm not sure how much of a possible performance downside it > has, but it does add instructions to potentially critical areas. > *As far as I know*, SMAP will be pushed into all CPUs over time. SMAP is already configurable, although the overhead on non-SMAP-enabled hardware is minimal (the CLAC/STAC instructions get patched out.) -hpa