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=-2.2 required=3.0 tests=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 78058C3A59E for ; Mon, 2 Sep 2019 11:13:20 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E69A5216C8 for ; Mon, 2 Sep 2019 11:13:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E69A5216C8 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 46MSB56Qd9zDqfL for ; Mon, 2 Sep 2019 21:13:17 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=permerror (mailfrom) smtp.mailfrom=kernel.crashing.org (client-ip=63.228.1.57; helo=gate.crashing.org; envelope-from=segher@kernel.crashing.org; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 46MS7x6SJvzDqX2 for ; Mon, 2 Sep 2019 21:11:25 +1000 (AEST) Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id x82BB7FG023249; Mon, 2 Sep 2019 06:11:07 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id x82BB5Mw023248; Mon, 2 Sep 2019 06:11:05 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Mon, 2 Sep 2019 06:11:05 -0500 From: Segher Boessenkool To: Michael Ellerman Subject: Re: [RFC PATCH] powerpc: Convert ____flush_dcache_icache_phys() to C Message-ID: <20190902111105.GX31406@gate.crashing.org> References: <9887dada07278cb39051941d1a47d50349d9fde0.camel@au1.ibm.com> <87imqbtqlw.fsf@mpe.ellerman.id.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87imqbtqlw.fsf@mpe.ellerman.id.au> User-Agent: Mutt/1.4.2.3i X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org, Alastair D'Silva , linux-kernel@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Mon, Sep 02, 2019 at 11:48:59AM +1000, Michael Ellerman wrote: > "Alastair D'Silva" writes: > > On Wed, 2019-08-21 at 22:27 +0200, Christophe Leroy wrote: > >> Can we be 100% sure that GCC won't add any code accessing some > >> global data or stack while the Data MMU is OFF ? > > > > +mpe > > > > I'm not sure how we would go about making such a guarantee, but I've > > tied every variable used to a register and addr is passed in a > > register, so there is no stack usage, and every call in there only > > operates on it's operands. > > That's not safe, I can believe it happens to work but the compiler > people will laugh at us if it ever breaks. Yes. Sorry. > Let's leave it in asm. +1 The asm is simpler, more readable, more maintainable, and perhaps more performant even. Plus the being-laughed-at issue. Segher