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=-4.0 required=3.0 tests=BAYES_00,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 A3B6DC433E6 for ; Thu, 14 Jan 2021 08:21:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 60905239EC for ; Thu, 14 Jan 2021 08:21:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727778AbhANIVg (ORCPT ); Thu, 14 Jan 2021 03:21:36 -0500 Received: from mail.kernel.org ([198.145.29.99]:33110 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726204AbhANIVg (ORCPT ); Thu, 14 Jan 2021 03:21:36 -0500 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (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 15CF22343F; Thu, 14 Jan 2021 08:20:55 +0000 (UTC) Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.94) (envelope-from ) id 1kzxsC-007S2r-Pq; Thu, 14 Jan 2021 08:20:53 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Date: Thu, 14 Jan 2021 08:20:52 +0000 From: Marc Zyngier To: Srinivas Ramana Cc: catalin.marinas@arm.com, will@kernel.org, pajay@qti.qualcomm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-arm-msm@vger.kernel.org Subject: Re: [PATCH 0/3] arm64: cpufeature: Add filter function to control In-Reply-To: References: <1610152163-16554-1-git-send-email-sramana@codeaurora.org> <6dfdf691b5ed57df81c4c61422949af5@misterjones.org> User-Agent: Roundcube Webmail/1.4.9 Message-ID: <7b53c01dd5afcb29679c3a9cf72407a9@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: sramana@codeaurora.org, catalin.marinas@arm.com, will@kernel.org, pajay@qti.qualcomm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-arm-msm@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On 2021-01-14 07:15, Srinivas Ramana wrote: > Hi Marc, > > On 1/11/2021 5:40 AM, Marc Zyngier wrote: >> Hi Srinivas, >> >> On 2021-01-09 00:29, Srinivas Ramana wrote: >>> This patchset adds a control function for cpufeature framework >>> so that the feature can be controlled at runtime. >>> >>> Defer PAC on boot core and use the filter function added to disable >>> PAC from command line. This will help toggling the feature on systems >>> that do not support PAC or where PAC needs to be disabled at runtime, >>> without modifying the core kernel. >>> >>> The idea of adding the filter function for cpufeature is taken from >>> https://lore.kernel.org/linux-arm-kernel/20200515171612.1020-25-catalin.marinas@arm.com/ >>> https://lore.kernel.org/linux-arm-kernel/20200515171612.1020-24-catalin.marinas@arm.com/ >>> Srinivas Ramana (3): >>>   arm64: Defer enabling pointer authentication on boot core >>>   arm64: cpufeature: Add a filter function to cpufeature >>>   arm64: Enable control of pointer authentication using early param >>> >>>  Documentation/admin-guide/kernel-parameters.txt |  6 +++ >>>  arch/arm64/include/asm/cpufeature.h             |  8 +++- >>>  arch/arm64/include/asm/pointer_auth.h           | 10 +++++ >>>  arch/arm64/include/asm/stackprotector.h         |  1 + >>>  arch/arm64/kernel/cpufeature.c                  | 53 >>> +++++++++++++++++++------ >>>  arch/arm64/kernel/head.S                        |  4 -- >>>  6 files changed, 64 insertions(+), 18 deletions(-) >> >> I've been working for some time on a similar series to allow a feature >> set to be disabled during the early boot phase, initially to prevent >> booting a kernel with VHE, but the mechanism is generic enough to >> deal with most architectural features. >> >> I took the liberty to lift your first patch and to add it to my >> series[1], >> further allowing PAuth to be disabled at boot time on top of BTI and >> VHE. >> >> I'd appreciate your comments on this. > Thanks for sending this series. It seems to be more flexible compared > you what we did. > Following your discussion on allowing EXACT ftr_reg values. > > > Btw, do you have plan to add MTE in similar lines to control the > feature? > We may be needing this on some systems. I don't have any need for this at the moment, as my initial goal was to enable a different boot flow for VHE. The BTI "support" was added as a way to demonstrate the use of __read_sysreg_by_encoding(), and your patches were a good opportunity to converge on a single solution. But if you write the patches that do that, I can add them to the series, and Catalin/Will can decide whether they want to take them. Thanks, M. -- Jazz is not dead. It just smells funny...