From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934145AbaFSSD3 (ORCPT ); Thu, 19 Jun 2014 14:03:29 -0400 Received: from terminus.zytor.com ([198.137.202.10]:60730 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933226AbaFSSD1 (ORCPT ); Thu, 19 Jun 2014 14:03:27 -0400 Message-ID: <53A325CE.5020206@zytor.com> Date: Thu, 19 Jun 2014 11:02:54 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Dave Hansen , Borislav Petkov , Qiaowei Ren CC: Thomas Gleixner , Ingo Molnar , x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v6 03/10] x86, mpx: add macro cpu_has_mpx References: <1403084656-27284-1-git-send-email-qiaowei.ren@intel.com> <1403084656-27284-4-git-send-email-qiaowei.ren@intel.com> <20140618095739.GA24419@pd.tnic> <53A1A3A5.9010109@intel.com> <53A1A942.1090001@zytor.com> <53A1BD95.10701@intel.com> In-Reply-To: <53A1BD95.10701@intel.com> X-Enigmail-Version: 1.6 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 06/18/2014 09:25 AM, Dave Hansen wrote: > On 06/18/2014 07:59 AM, H. Peter Anvin wrote: >> On 06/18/2014 07:35 AM, Dave Hansen wrote: >>> It looks like static_cpu_has() is the right thing to use instead of >>> boot_cpu_has(). But, this doesn't just obfuscate things. >>> >>> We actually _want_ the compiler to cull code out when the config option >>> is off. Things like do_bounds() will see code savings with _some_ kind >>> of #ifdef rather than using static_cpu_has(). >>> >>> So, we can either use the well worn, consistent with other features in >>> x86, cpu_has_$foo approach. Or, we can roll our own macros. >> >> We could do something like: >> >> #define MPX_ENABLED (IS_ENABLED(CONFIG_X86_MPX) && >> static_cpu_has(X86_FEATURE_MPX)) > > How about something like the attached patch? > > This lets us use static_cpu_has() for the checks, and allows us to > easily add new checks for other features that might be compile-time > disabled. > Hmm... I would like something similar to required-features.h which reflect features which *cannot* be enabled or will always be ignored; we actually already have a handful of those. -hpa