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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,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 B9B09C432C0 for ; Tue, 26 Nov 2019 09:53:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8CFDE207DD for ; Tue, 26 Nov 2019 09:53:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727638AbfKZJxq convert rfc822-to-8bit (ORCPT ); Tue, 26 Nov 2019 04:53:46 -0500 Received: from eu-smtp-delivery-151.mimecast.com ([207.82.80.151]:24428 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727397AbfKZJxq (ORCPT ); Tue, 26 Nov 2019 04:53:46 -0500 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-214-4-9H7vGLMDuAXhSNvLlglQ-1; Tue, 26 Nov 2019 09:53:39 +0000 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Tue, 26 Nov 2019 09:53:38 +0000 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Tue, 26 Nov 2019 09:53:38 +0000 From: David Laight To: 'Fenghua Yu' , Thomas Gleixner , Ingo Molnar , Borislav Petkov , H Peter Anvin , Andy Lutomirski , Peter Zijlstra , Ashok Raj , Tony Luck , Ravi V Shankar CC: linux-kernel , x86 Subject: RE: [PATCH v2 2/4] xen-pcifront: Align address of flags to size of unsigned long Thread-Topic: [PATCH v2 2/4] xen-pcifront: Align address of flags to size of unsigned long Thread-Index: AQHVo8bqrfjaxnvKokKft9QerImLSKedNnnQ Date: Tue, 26 Nov 2019 09:53:38 +0000 Message-ID: <10982a76b2b9431f90d4d8c41c8ad48f@AcuMS.aculab.com> References: <1574710984-208305-1-git-send-email-fenghua.yu@intel.com> <1574710984-208305-3-git-send-email-fenghua.yu@intel.com> In-Reply-To: <1574710984-208305-3-git-send-email-fenghua.yu@intel.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-MC-Unique: 4-9H7vGLMDuAXhSNvLlglQ-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Fenghua Yu > Sent: 25 November 2019 19:43 > The address of "flags" is passed to atomic bitops which require the > address is aligned to size of unsigned long. > > Signed-off-by: Fenghua Yu > --- > include/xen/interface/io/pciif.h | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/include/xen/interface/io/pciif.h b/include/xen/interface/io/pciif.h > index d9922ae36eb5..639d5fb484a3 100644 > --- a/include/xen/interface/io/pciif.h > +++ b/include/xen/interface/io/pciif.h > @@ -103,8 +103,11 @@ struct xen_pcie_aer_op { > uint32_t devfn; > }; > struct xen_pci_sharedinfo { > - /* flags - XEN_PCIF_* */ > - uint32_t flags; > + /* flags - XEN_PCIF_*. Force alignment for atomic bit operations. */ > + union { > + uint32_t flags; > + unsigned long flags_alignment; > + }; This is papering over the cracks..... Changing flags to be 'unsigned long' and removing the casts is correct. Either that or change to code to use simple assignments on the single 'flags' variable instead of the relatively expensive function calls that are designed for large arrays of bits. David. - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)