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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 32C9CC433DB for ; Wed, 17 Mar 2021 13:20:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E1E1364F50 for ; Wed, 17 Mar 2021 13:20:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230051AbhCQNUD convert rfc822-to-8bit (ORCPT ); Wed, 17 Mar 2021 09:20:03 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.86.151]:39784 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230505AbhCQNTb (ORCPT ); Wed, 17 Mar 2021 09:19:31 -0400 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-55-3sGq2adXMGirCyN93jbuVw-1; Wed, 17 Mar 2021 13:19:24 +0000 X-MC-Unique: 3sGq2adXMGirCyN93jbuVw-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Wed, 17 Mar 2021 13:19:23 +0000 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.012; Wed, 17 Mar 2021 13:19:23 +0000 From: David Laight To: "'Martin K. Petersen'" , Arnd Bergmann CC: "Don.Brace@microchip.com" , Sergei Trofimovich , "linux-kernel@vger.kernel.org" , "linux-ia64@vger.kernel.org" , "storagedev@microchip.com" , linux-scsi , "jszczype@redhat.com" , "Scott.Benesh@microchip.com" , "Scott.Teel@microchip.com" , "thenzl@redhat.com" , "John Paul Adrian Glaubitz" Subject: RE: [PATCH] hpsa: fix boot on ia64 (atomic_t alignment) Thread-Topic: [PATCH] hpsa: fix boot on ia64 (atomic_t alignment) Thread-Index: AQHXGtT0rSNa450uZ0SMu8nCYRzH7aqIKWKQ Date: Wed, 17 Mar 2021 13:19:23 +0000 Message-ID: <4b2a64d91c4c478f881d9713cac5001b@AcuMS.aculab.com> References: <5532f9ab-7555-d51b-f4d5-f9b72a61f248@redhat.com> <20210312222718.4117508-1-slyfox@gentoo.org> In-Reply-To: Accept-Language: en-GB, 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 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Martin K. Petersen > Sent: 17 March 2021 02:26 > > Arnd, > > > Actually that still feels wrong: the annotation of the struct is to > > pack every member, which causes the access to be done in byte units on > > architectures that do not have hardware unaligned load/store > > instructions, at least for things like atomic_read() that does not go > > through a cmpxchg() or ll/sc cycle. > > > This change may fix itanium, but it's still not correct. Other > > architectures would have already been broken before the recent change, > > but that's not a reason against fixing them now. > > I agree. I understand why there are restrictions on fields consumed by > the hardware. But for fields internal to the driver the packing doesn't > make sense to me. Jeepers -- that global #pragma pack(1) is bollocks. I think there are a couple of __u64 that are 32bit aligned. Just marking those field __packed __aligned(4) should have the desired effect. Or use a typedef for '__u64 with 32bit alignment'. (There probably ought to be one in types.h) Then add compile-time asserts that any non-trivial structures the hardware accesses are the right size. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)