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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 58FF3C433EF for ; Wed, 2 Mar 2022 11:46:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=0KR50jPf2OxvhqJlweBoe0RpEoEit07nQrBD5lsGPIQ=; b=YKrlfw+JKM840N Gvt+03asHAAU/jsBybweMVqfSMBVGLapSKSodlNbRR1zGnq9qIz/kYHXYHGaGKScxgDSXANfAk5Oa +C8vqjz5j2qnQdUWtjrdqyIkZrcoaXq+NGvFGRkVDjw/SS/mfnVdfLR1hHV3DW4VEMdMZvLuSnMsQ 12iC+AD/IS6gA7noTLcdLn7MTBYDCrRfUNK5DDa9Uiz+XKBa1Spt1VPiT3IzKUIUcMylPBptoY4M3 8FNl40pgE+NJIlLHSxtoVyb3c0sftjjF15u2I86ttaSNyyCBLd9lsoONKq5ztlVOqaTOgCeZmSuNL vly19kaX4p36mi9gQpTA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nPNPs-002WLp-35; Wed, 02 Mar 2022 11:45:12 +0000 Received: from ams.source.kernel.org ([2604:1380:4601:e00::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nPNPh-002WID-CD for linux-arm-kernel@lists.infradead.org; Wed, 02 Mar 2022 11:45:02 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id D75CDB81F98; Wed, 2 Mar 2022 11:44:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3C676C340E9; Wed, 2 Mar 2022 11:44:57 +0000 (UTC) Date: Wed, 2 Mar 2022 11:44:53 +0000 From: Catalin Marinas To: Evgenii Stepanov Cc: Mark Brown , Will Deacon , Joey Gouly , Branislav Rankov , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v1 4/4] arm64/mte: Add userspace interface for enabling asymmetric mode Message-ID: References: <20220127195712.748150-1-broonie@kernel.org> <20220127195712.748150-5-broonie@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220302_034501_652227_3D9EE02D X-CRM114-Status: GOOD ( 17.38 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Mar 01, 2022 at 04:52:01PM -0800, Evgenii Stepanov wrote: > On Thu, Jan 27, 2022 at 07:57:12PM +0000, Mark Brown wrote: > > Since there PR_MTE_TCF_ values are a bitmask (allowing the kernel to choose > > between the multiple modes) and there are no free bits adjacent to the > > existing PR_MTE_TCF_ bits the set of bits used to specify the mode becomes > > disjoint. Programs using the new interface should be aware of this and > > programs that do not use it will not see any change in behaviour. > > Extending PR_MTE_TCF_MASK seems bad for backward compatibility. User > code may do "flags =& ~PR_MTE_TCF_MASK" to disable MTE; when compiled > against an old version of the header this would fail to remove the ASYMM > bit. But if the app is compiled against an old version, it wouldn't set MTE_CTRL_TCF_ASYMM either as it doesn't have the definition. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel