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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 B269FC3F2D1 for ; Thu, 5 Mar 2020 16:38:15 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 7DECA2146E for ; Thu, 5 Mar 2020 16:38:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7DECA2146E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 20F8B6B0005; Thu, 5 Mar 2020 11:38:15 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 1E5AF6B0006; Thu, 5 Mar 2020 11:38:15 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 122A66B0007; Thu, 5 Mar 2020 11:38:15 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0225.hostedemail.com [216.40.44.225]) by kanga.kvack.org (Postfix) with ESMTP id EC9D76B0005 for ; Thu, 5 Mar 2020 11:38:14 -0500 (EST) Received: from smtpin02.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id D27C08248047 for ; Thu, 5 Mar 2020 16:38:14 +0000 (UTC) X-FDA: 76561866108.02.party61_2adcc56107a45 X-HE-Tag: party61_2adcc56107a45 X-Filterd-Recvd-Size: 2876 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf13.hostedemail.com (Postfix) with ESMTP for ; Thu, 5 Mar 2020 16:38:14 +0000 (UTC) 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 AAC3930E; Thu, 5 Mar 2020 08:38:13 -0800 (PST) Received: from arrakis.emea.arm.com (arrakis.cambridge.arm.com [10.1.196.71]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3FFEE3F534; Thu, 5 Mar 2020 08:38:12 -0800 (PST) Date: Thu, 5 Mar 2020 16:38:10 +0000 From: Catalin Marinas To: Steven Price Cc: linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org, Richard Earnshaw , Szabolcs Nagy , Andrey Konovalov , Kevin Brodsky , Peter Collingbourne , linux-mm@kvack.org, Vincenzo Frascino , Will Deacon Subject: Re: [PATCH v2 04/19] arm64: mte: Use Normal Tagged attributes for the linear map Message-ID: <20200305163810.GC1729062@arrakis.emea.arm.com> References: <20200226180526.3272848-1-catalin.marinas@arm.com> <20200226180526.3272848-5-catalin.marinas@arm.com> <946fcd05-ba8f-90ec-d30b-458b327df59c@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <946fcd05-ba8f-90ec-d30b-458b327df59c@arm.com> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Mar 05, 2020 at 04:21:34PM +0000, Steven Price wrote: > On 26/02/2020 18:05, Catalin Marinas wrote: > > + if (system_supports_mte()) { > > + /* > > + * Changing the memory type between Normal and Normal-Tagged > > + * is safe since Tagged is considered a permission attribute > > + * from the mismatched attribute aliases perspective. > > + */ > > + if ((old & PTE_ATTRINDX_MASK) == PTE_ATTRINDX(MT_NORMAL) || > > + (old & PTE_ATTRINDX_MASK) == PTE_ATTRINDX(MT_NORMAL_TAGGED) || > > + (new & PTE_ATTRINDX_MASK) == PTE_ATTRINDX(MT_NORMAL) || > > + (new & PTE_ATTRINDX_MASK) == PTE_ATTRINDX(MT_NORMAL_TAGGED)) > > + mask |= PTE_ATTRINDX_MASK; > > + } > > + > > return ((old ^ new) & ~mask) == 0; > > } > > This is much more permissive than I would expect. If either the old or > new memory type is NORMAL (or NORMAL_TAGGED) then the memory type is > ignored altogether. > > Should this check be: > > if (((old & PTE_ATTRINDX_MASK) == PTE_ATTRINDX(MT_NORMAL) || > (old & PTE_ATTRINDX_MASK) == PTE_ATTRINDX(MT_NORMAL_TAGGED)) && > ((new & PTE_ATTRINDX_MASK) == PTE_ATTRINDX(MT_NORMAL) || > (new & PTE_ATTRINDX_MASK) == PTE_ATTRINDX(MT_NORMAL_TAGGED))) You are right, I think my patch allows many other memory type combinations. Thanks. -- Catalin