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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 80C53C433B4 for ; Fri, 14 May 2021 11:53:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5E3E961205 for ; Fri, 14 May 2021 11:53:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232376AbhENLy4 (ORCPT ); Fri, 14 May 2021 07:54:56 -0400 Received: from gate.crashing.org ([63.228.1.57]:37389 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231839AbhENLy4 (ORCPT ); Fri, 14 May 2021 07:54:56 -0400 Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 14EBmDhI029374; Fri, 14 May 2021 06:48:14 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 14EBmDxj029373; Fri, 14 May 2021 06:48:13 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Fri, 14 May 2021 06:48:13 -0500 From: Segher Boessenkool To: Arnd Bergmann Cc: linux-arch@vger.kernel.org, Arnd Bergmann , Vineet Gupta , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Paul Mackerras , Linus Torvalds Subject: Re: [PATCH v2 05/13] powerpc: use linux/unaligned/le_struct.h on LE power7 Message-ID: <20210514114813.GJ10366@gate.crashing.org> References: <20210514100106.3404011-1-arnd@kernel.org> <20210514100106.3404011-6-arnd@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210514100106.3404011-6-arnd@kernel.org> User-Agent: Mutt/1.4.2.3i Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org Hi Arnd, On Fri, May 14, 2021 at 12:00:53PM +0200, Arnd Bergmann wrote: > Little-endian POWER7 kernels disable > CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS because that is not supported on > the hardware, but the kernel still uses direct load/store for explicti > get_unaligned()/put_unaligned(). > > I assume this is a mistake that leads to power7 having to trap and fix > up all these unaligned accesses at a noticeable performance cost. > > The fix is completely trivial, just remove the file and use the > generic version that gets it right. LE p7 isn't supported (it requires special firmware), and no one uses it anymore, also not for development. It was used for powerpc64le-linux development before p8 was widely available. Segher