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=unavailable 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 EA5CBC433E7 for ; Tue, 20 Oct 2020 12:31:16 +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 05C3C22265 for ; Tue, 20 Oct 2020 12:31:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 05C3C22265 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 4CFtJw0C0mzDqMB for ; Tue, 20 Oct 2020 23:31:12 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=permerror (SPF Permanent Error: Unknown mechanism found: ip:192.40.192.88/32) 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]) by lists.ozlabs.org (Postfix) with ESMTP id 4CFt3d6kXQzDqJf for ; Tue, 20 Oct 2020 23:19:41 +1100 (AEDT) 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 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 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: linux-kernel@vger.kernel.org, mathieu.desnoyers@efficios.com, Paul Mackerras , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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