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=-8.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 F12F3C433DF for ; Tue, 20 Oct 2020 12:22:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8243D2222C for ; Tue, 20 Oct 2020 12:22:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2405853AbgJTMWu (ORCPT ); Tue, 20 Oct 2020 08:22:50 -0400 Received: from gate.crashing.org ([63.228.1.57]:52509 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2394268AbgJTMWu (ORCPT ); Tue, 20 Oct 2020 08:22:50 -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 09KCGBUp025510; Tue, 20 Oct 2020 07:16:16 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 09KCGAIq025509; Tue, 20 Oct 2020 07:16:10 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Tue, 20 Oct 2020 07:16:10 -0500 From: Segher Boessenkool To: Christophe Leroy Cc: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , mathieu.desnoyers@efficios.com, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 3/3] powerpc: Fix update form addressing in inline assembly Message-ID: <20201020121610.GZ2672@gate.crashing.org> References: <212d3bc4a52ca71523759517bb9c61f7e477c46a.1603179582.git.christophe.leroy@csgroup.eu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi! On Tue, Oct 20, 2020 at 07:40:09AM +0000, Christophe Leroy wrote: > In several places, inline assembly uses the "%Un" modifier > to enable the use of instruction with update form addressing, > but the associated "<>" constraint is missing. > > As mentioned in previous patch, this fails with gcc 4.9, so > "<>" can't be used directly. > > Use UPD_CONSTR macro everywhere %Un modifier is used. > > Signed-off-by: Christophe Leroy Oh well, it will be easy enough to remove this wart later, so Reviewed-by: Segher Boessenkool > --- a/arch/powerpc/include/asm/book3s/32/pgtable.h > +++ b/arch/powerpc/include/asm/book3s/32/pgtable.h > @@ -525,7 +525,7 @@ static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr, > stw%U0%X0 %2,%0\n\ > eieio\n\ > stw%U1%X1 %L2,%1" > - : "=m" (*ptep), "=m" (*((unsigned char *)ptep+4)) > + : "=m"UPD_CONSTR (*ptep), "=m"UPD_CONSTR (*((unsigned char *)ptep+4)) > : "r" (pte) : "memory"); Here it would pre-increment ptep+4. That can never be something useful afaics? The order the two operands are (either or not) pre-modified in the asm is not specified (GCC does not parse the asm template, by design), so I fail to see how this could ever work. > --- a/arch/powerpc/include/asm/nohash/pgtable.h > +++ b/arch/powerpc/include/asm/nohash/pgtable.h > @@ -200,7 +200,7 @@ static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr, > stw%U0%X0 %2,%0\n\ > eieio\n\ > stw%U1%X1 %L2,%1" > - : "=m" (*ptep), "=m" (*((unsigned char *)ptep+4)) > + : "=m"UPD_CONSTR (*ptep), "=m"UPD_CONSTR (*((unsigned char *)ptep+4)) > : "r" (pte) : "memory"); Same here. The rest looks fine. Segher