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=-5.5 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 2B06AC433E1 for ; Mon, 20 Jul 2020 20:26:54 +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 D509E207DF for ; Mon, 20 Jul 2020 20:26:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D509E207DF 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 4B9YDB69N0zDqNx for ; Tue, 21 Jul 2020 06:26:50 +1000 (AEST) 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 4B9YB72jcmzDqHj for ; Tue, 21 Jul 2020 06:25:03 +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 06KKOrG5032543; Mon, 20 Jul 2020 15:24:53 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 06KKOqCj032537; Mon, 20 Jul 2020 15:24:52 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Mon, 20 Jul 2020 15:24:52 -0500 From: Segher Boessenkool To: Laurent Dufour Subject: Re: [RFC PATCH] powerpc/pseries/svm: capture instruction faulting on MMIO access, in sprg0 register Message-ID: <20200720202452.GN30544@gate.crashing.org> References: <1594888333-9370-1-git-send-email-linuxram@us.ibm.com> <18e3bcee-8a3a-bd13-c995-8e4168471f74@linux.ibm.com> <20200720201041.GM30544@gate.crashing.org> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200720201041.GM30544@gate.crashing.org> 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: aik@ozlabs.ru, Ram Pai , kvm-ppc@vger.kernel.org, bharata@linux.ibm.com, sathnaga@linux.vnet.ibm.com, sukadev@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org, bauerman@linux.ibm.com, david@gibson.dropbear.id.au Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Mon, Jul 20, 2020 at 03:10:41PM -0500, Segher Boessenkool wrote: > On Mon, Jul 20, 2020 at 11:39:56AM +0200, Laurent Dufour wrote: > > Le 16/07/2020 à 10:32, Ram Pai a écrit : > > >+ if (is_secure_guest()) { \ > > >+ __asm__ __volatile__("mfsprg0 %3;" \ > > >+ "lnia %2;" \ > > >+ "ld %2,12(%2);" \ > > >+ "mtsprg0 %2;" \ > > >+ "sync;" \ > > >+ #insn" %0,%y1;" \ > > >+ "twi 0,%0,0;" \ > > >+ "isync;" \ > > >+ "mtsprg0 %3" \ > > >+ : "=r" (ret) \ > > >+ : "Z" (*addr), "r" (0), "r" (0) \ > > > > I'm wondering if SPRG0 is restored to its original value. > > You're using the same register (r0) for parameters 2 and 3, so when doing > > lnia %2, you're overwriting the SPRG0 value you saved in r0 just earlier. > > It is putting the value 0 in the registers the compiler chooses for > operands 2 and 3. But operand 3 is written, while the asm says it is an > input. It needs an earlyclobber as well. > > > It may be clearer to use explicit registers for %2 and %3 and to mark them > > as modified for the compiler. > > That is not a good idea, imnsho. (The explicit register number part, I mean; operand 2 should be an output as well, yes.) Segher