From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E1336C6778A for ; Fri, 29 Jun 2018 21:11:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 885CB23FF5 for ; Fri, 29 Jun 2018 21:11:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 885CB23FF5 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935779AbeF2VLM (ORCPT ); Fri, 29 Jun 2018 17:11:12 -0400 Received: from mga05.intel.com ([192.55.52.43]:11349 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932345AbeF2VLL (ORCPT ); Fri, 29 Jun 2018 17:11:11 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 29 Jun 2018 14:11:10 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.51,287,1526367600"; d="scan'208";a="51568474" Received: from romley-ivt3.sc.intel.com ([172.25.110.60]) by fmsmga008.fm.intel.com with ESMTP; 29 Jun 2018 14:11:10 -0700 Date: Fri, 29 Jun 2018 14:10:30 -0700 From: Fenghua Yu To: Dave Hansen Cc: Fenghua Yu , Thomas Gleixner , Ingo Molnar , H Peter Anvin , Ashok Raj , Alan Cox , Peter Zijlstra , Rafael Wysocki , Tony Luck , Ravi V Shankar , linux-kernel , x86 Subject: Re: [PATCH v2 2/4] x86/split_lock: Align x86_capability to unsigned long to avoid split locked access Message-ID: <20180629211030.GB68178@romley-ivt3.sc.intel.com> References: <1530282807-66555-1-git-send-email-fenghua.yu@intel.com> <1530282807-66555-3-git-send-email-fenghua.yu@intel.com> <20180629190346.GO18979@romley-ivt3.sc.intel.com> <20180629203844.GA68178@romley-ivt3.sc.intel.com> <8fdfb671-f223-163b-12cd-3c97d94f91b4@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8fdfb671-f223-163b-12cd-3c97d94f91b4@intel.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 29, 2018 at 01:48:45PM -0700, Dave Hansen wrote: > On 06/29/2018 01:38 PM, Fenghua Yu wrote: > > How to handle data that is used in generic code which can be used on > > non-Intel platform? For exmple, if I do this change for struct efi in > > include/linux/efi.h because set_bit() sets bits in efi.flags: > > - unsigned long flags; > > + unsigned long flags __aligned(unsigned long); > > } efi; > > > > People may argue that the alignment unnecessarily increases size of 'efi' > > on non-Intel platform which doesn't have split lock issue. Do we care this > > argument? > > Unaligned memory accesses are bad, pretty much universally. This is a > general good practice that we should have been doing anyway. Let folks > complain. Don't let it stop you. > > Also, look at the size of that structure. Look at how many pointers it > has. Do you think *anyone* is going to complain about an extra 4 bytes > in a 400-byte structure? > > > Another question, there will be a bunch of one-line changes for > > the alignment (i.e. adding __aligned(unsigned long)) in various files. > > Will the changes be put in one big patch or in separate one-liner patches? > > Just group them logically. Sure. Thanks. -Fenghua