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=-5.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,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 DE3B6C47082 for ; Thu, 3 Jun 2021 14:32:31 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id A684F613F1 for ; Thu, 3 Jun 2021 14:32:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A684F613F1 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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=Dl7uGI44kmKFuP0h+GBEXIio1Z6HNCbkpEqStvgiSaI=; b=H7gg5rQW+WayZz erSOOr5Tlr9Gb+6vi+1wDitPHy0cS89/XLLlMEO7DLtW8A+NAi2jNSO1shBi2tUcVKXumLku5dSAs gkQYnHwyry8QS5FOl0576dRv/kqm82MF7nQ7NZPMOYMx6tq/Cpw/5+FiAS7UZ5tCbBnPnrAGaaQGr 3RZ4DQYC0ZBuIXnUG4w3xu5Czony/Vhxq3HkeqkJIlOOTuDO1KTkdT2fVTf/ygWPI7Q4GlHAAaKIl ktIKe1Sjnr+is232NUxu5y5Te2nGCbEhXUdrrjH3piVTr2Kn166yCcqX9ALUpSgB47IwxQEeIk0RK r8mIWVVFDmSYl07Tzqlw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1looMj-009AwS-6M; Thu, 03 Jun 2021 14:30:33 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1looMa-009Au1-TL for linux-arm-kernel@lists.infradead.org; Thu, 03 Jun 2021 14:30:30 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id 73EF4613B8; Thu, 3 Jun 2021 14:30:23 +0000 (UTC) Date: Thu, 3 Jun 2021 15:30:21 +0100 From: Catalin Marinas To: Peter Collingbourne Cc: Vincenzo Frascino , Will Deacon , Evgenii Stepanov , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] arm64: mte: allow async MTE to be upgraded to sync on a per-CPU basis Message-ID: <20210603143020.GD20338@arm.com> References: <20210602232445.3829248-1-pcc@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210602232445.3829248-1-pcc@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210603_073025_000342_1C4F10B3 X-CRM114-Status: GOOD ( 13.22 ) 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 Hi Peter, On Wed, Jun 02, 2021 at 04:24:45PM -0700, Peter Collingbourne wrote: > On some CPUs the performance of MTE in synchronous mode is the same > as that of asynchronous mode. This makes it worthwhile to enable > synchronous mode on those CPUs when asynchronous mode is requested, > in order to gain the error detection benefits of synchronous mode > without the performance downsides. Therefore, make it possible for CPUs > to opt into upgrading to synchronous mode via a new mte-prefer-sync > device tree attribute. As Vincenzo said, there's an ABI change which I don't particularly like. I think the current PR_MTE_TCF_* should be honoured as they described. We could introduce a new control, PR_MTE_TCF_DYNAMIC (or a better name) that would cover both your mixed system or some future scenario where we want to switch between async and sync (and the new asymmetric mode in 8.7) at run-time via some other control/timer and transparently from the application. But that would be an application opt-in. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel