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=-2.3 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 4C4B6C43331 for ; Mon, 11 Nov 2019 17:16:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1F88321655 for ; Mon, 11 Nov 2019 17:16:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726946AbfKKRQp (ORCPT ); Mon, 11 Nov 2019 12:16:45 -0500 Received: from foss.arm.com ([217.140.110.172]:48234 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726845AbfKKRQp (ORCPT ); Mon, 11 Nov 2019 12:16:45 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E2D0731B; Mon, 11 Nov 2019 09:16:44 -0800 (PST) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8ED4D3F534; Mon, 11 Nov 2019 09:16:43 -0800 (PST) Date: Mon, 11 Nov 2019 17:16:35 +0000 From: Mark Rutland To: Steven Price Cc: Marc Zyngier , Suzuki K Poulose , Catalin Marinas , linux-kernel@vger.kernel.org, James Morse , Julien Thierry , Will Deacon , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 1/2] arm64: Rename WORKAROUND_1165522 to SPECULATIVE_AT Message-ID: <20191111171621.GA30274@lakrids.cambridge.arm.com> References: <20191111141157.55062-1-steven.price@arm.com> <20191111141157.55062-2-steven.price@arm.com> <160a852027f4481cc63aed72c4f4a409@www.loen.fr> <013eec05-b558-d97a-bf95-248a62f25dc5@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <013eec05-b558-d97a-bf95-248a62f25dc5@arm.com> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 11, 2019 at 04:07:39PM +0000, Steven Price wrote: > On 11/11/2019 15:42, Marc Zyngier wrote: > >> +config ARM64_WORKAROUND_SPECULATIVE_AT > >> +    bool > >> + > >>  config ARM64_ERRATUM_1165522 > >>      bool "Cortex-A76: Speculative AT instruction using out-of-context > >> translation regime could cause subsequent request to generate an > >> incorrect translation" > >>      default y > >> +    select ARM64_WORKAROUND_SPECULATIVE_AT > > > > I'd object that ARM64_ERRATUM_1319367 (and its big brother 1319537) > > are also related to speculative AT execution, and yet are not covered > > by this configuration symbol. > > Good point. > > > I can see three solutions to this: > > > > - Either you call it SPECULATIVE_AT_VHE and introduce SPECULATIVE_AT_NVHE > >   for symmetry > > Tempting... FWIW, this sounds fine to me. > > - Or you make SPECULATIVE_AT cover all the speculative AT errata, which > >   may or may not work... > > This actually sounds the neatest, but I'm not sure whether there's going > to be any conflicts between VHE/NVHE. I'll prototype this and see how > ugly it is. > > > - Or even better, you just ammend the documentation to say that 1165522 > >   also covers the newly found A55 one (just like we have for A57/A72) > > Well Mark Rutland disliked my initial thoughts about just including both > errata in one option like that - hence the refactoring in this patch. > Although of course that's exactly what's happened with 1319367/1319537... My view on this is that using one erratum config symbol to cover the workaround for another is more confusing than having a level of indirection, and I would've preferred the indirection for that case too. > > What do you think? > > I'll have a go at SPECULATIVE_AT covering both VHE/NVHE - from an > initial look it seems like it should work and it would be neat if it > does. In particular it should avoid the necessity to require VHE when > the erratum is present. > > Otherwise I guess SPECULATIVE_AT_{,N}VHE is probably second best. Both sound good to me. Thanks for dealing with this! Mark.