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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 4CE64C6778A for ; Fri, 29 Jun 2018 20:48:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0B343249B7 for ; Fri, 29 Jun 2018 20:48:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0B343249B7 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 S937472AbeF2Ust (ORCPT ); Fri, 29 Jun 2018 16:48:49 -0400 Received: from mga01.intel.com ([192.55.52.88]:49023 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S937458AbeF2Uss (ORCPT ); Fri, 29 Jun 2018 16:48:48 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 29 Jun 2018 13:48:47 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.51,287,1526367600"; d="scan'208";a="68887673" Received: from ray.jf.intel.com (HELO [10.7.201.18]) ([10.7.201.18]) by orsmga001.jf.intel.com with ESMTP; 29 Jun 2018 13:48:47 -0700 Subject: Re: [PATCH v2 2/4] x86/split_lock: Align x86_capability to unsigned long to avoid split locked access To: Fenghua Yu , Thomas Gleixner 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> Cc: Ingo Molnar , H Peter Anvin , Ashok Raj , Alan Cox , Peter Zijlstra , Rafael Wysocki , Tony Luck , Ravi V Shankar , linux-kernel , x86 From: Dave Hansen Openpgp: preference=signencrypt Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <20180629203844.GA68178@romley-ivt3.sc.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.