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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 54E92C433E0 for ; Mon, 18 May 2020 11:31:11 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1630420758 for ; Mon, 18 May 2020 11:31:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="XF7NkBh2" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1630420758 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 947ED900003; Mon, 18 May 2020 07:31:10 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8D078900002; Mon, 18 May 2020 07:31:10 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 771B7900003; Mon, 18 May 2020 07:31:10 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0041.hostedemail.com [216.40.44.41]) by kanga.kvack.org (Postfix) with ESMTP id 5A3D3900002 for ; Mon, 18 May 2020 07:31:10 -0400 (EDT) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 13A04181AEF1D for ; Mon, 18 May 2020 11:31:10 +0000 (UTC) X-FDA: 76829623500.25.twist33_4458f940fa227 X-HE-Tag: twist33_4458f940fa227 X-Filterd-Recvd-Size: 3600 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf42.hostedemail.com (Postfix) with ESMTP for ; Mon, 18 May 2020 11:31:09 +0000 (UTC) Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D8B0920756; Mon, 18 May 2020 11:31:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589801468; bh=mA5LuL+NZ4U22EpIeu1yY/QuHzmG+4ZlK35nDxAZ3lY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=XF7NkBh2RpP7Djhlw6gtpIkyVTqRimk+VriVrbaCTcWm/aslkIwjKrKCrs5T2jQ4v B9xYMQiqzJR3hkd0a/BLad5a4SW3AkDSXqzrObZQ4NfAO9jrtvsYsOiJ/lEIeuhY3z c01YbNXnW0VfZBr3F1izfcNFuOr49q89HEZl1o5I= Date: Mon, 18 May 2020 12:31:03 +0100 From: Will Deacon To: Vladimir Murzin Cc: Catalin Marinas , linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org, Szabolcs Nagy , Andrey Konovalov , Kevin Brodsky , Peter Collingbourne , linux-mm@kvack.org, Vincenzo Frascino , Dave P Martin Subject: Re: [PATCH v4 24/26] arm64: mte: Introduce early param to disable MTE support Message-ID: <20200518113103.GA32394@willie-the-truck> References: <20200515171612.1020-1-catalin.marinas@arm.com> <20200515171612.1020-25-catalin.marinas@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) 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 Mon, May 18, 2020 at 12:26:30PM +0100, Vladimir Murzin wrote: > On 5/15/20 6:16 PM, Catalin Marinas wrote: > > For performance analysis it may be desirable to disable MTE altogether > > via an early param. Introduce arm64.mte_disable and, if true, filter out > > the sanitised ID_AA64PFR1_EL1.MTE field to avoid exposing the HWCAP to > > user. > > > > Signed-off-by: Catalin Marinas > > Cc: Will Deacon > > --- > > > > Notes: > > New in v4. > > > > Documentation/admin-guide/kernel-parameters.txt | 4 ++++ > > arch/arm64/kernel/cpufeature.c | 11 +++++++++++ > > 2 files changed, 15 insertions(+) > > > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > > index f2a93c8679e8..7436e7462b85 100644 > > --- a/Documentation/admin-guide/kernel-parameters.txt > > +++ b/Documentation/admin-guide/kernel-parameters.txt > > @@ -373,6 +373,10 @@ > > arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards > > Format: ,, > > > > + arm64.mte_disable= > > + [ARM64] Disable Linux support for the Memory > > + Tagging Extension (both user and in-kernel). > > + > > Should it really to take parameter (on/off/true/false)? It may lead to expectation > that arm64.mte_disable=false should enable MT and, yes, double negatives make it > look ugly, so if we do need parameter, can it be arm64.mte=on/off/true/false? I don't think "performance analysis" is a good justification for this parameter tbh. We don't tend to add these options for other architectural features, and I don't see why MTE is any different in this regard. Will