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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS 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 4FF36C169C4 for ; Wed, 6 Feb 2019 21:08:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 24893218B0 for ; Wed, 6 Feb 2019 21:08:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726977AbfBFVIW (ORCPT ); Wed, 6 Feb 2019 16:08:22 -0500 Received: from foss.arm.com ([217.140.101.70]:58202 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726596AbfBFVIV (ORCPT ); Wed, 6 Feb 2019 16:08:21 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 36D9AEBD; Wed, 6 Feb 2019 13:08:21 -0800 (PST) Received: from [192.168.3.111] (usa-sjc-mx-foss1.foss.arm.com [217.140.101.70]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 83F213F675; Wed, 6 Feb 2019 13:08:18 -0800 (PST) Subject: Re: [PATCH v4 01/12] Documentation: Document arm64 kpti control To: Jeremy Linton Cc: linux-arm-kernel@lists.infradead.org, stefan.wahren@i2se.com, Jonathan Corbet , mlangsdo@redhat.com, linux-doc@vger.kernel.org, suzuki.poulose@arm.com, marc.zyngier@arm.com, catalin.marinas@arm.com, julien.thierry@arm.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, steven.price@arm.com, ykaukab@suse.de, dave.martin@arm.com, shankerd@codeaurora.org References: <20190125180711.1970973-1-jeremy.linton@arm.com> <20190125180711.1970973-2-jeremy.linton@arm.com> <20190130180247.15ab0577@donnerap.cambridge.arm.com> <69fceac6-7e83-7b38-44fb-2c02245f51df@arm.com> From: =?UTF-8?Q?Andr=c3=a9_Przywara?= Organization: ARM Ltd. Message-ID: <7bf0faad-1064-69cb-32fe-1782e6c742d2@arm.com> Date: Wed, 6 Feb 2019 21:06:30 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.0 MIME-Version: 1.0 In-Reply-To: <69fceac6-7e83-7b38-44fb-2c02245f51df@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/02/2019 19:24, Jeremy Linton wrote: > Hi, > > > I just realized I replied to this off-list. > > On 01/30/2019 12:02 PM, Andre Przywara wrote: >> On Fri, 25 Jan 2019 12:07:00 -0600 >> Jeremy Linton wrote: >> >> Hi, >> >>> For a while Arm64 has been capable of force enabling >>> or disabling the kpti mitigations. Lets make sure the >>> documentation reflects that. >>> >>> Signed-off-by: Jeremy Linton >>> Cc: Jonathan Corbet >>> Cc: linux-doc@vger.kernel.org >>> --- >>>   Documentation/admin-guide/kernel-parameters.txt | 6 ++++++ >>>   1 file changed, 6 insertions(+) >>> >>> diff --git a/Documentation/admin-guide/kernel-parameters.txt >>> b/Documentation/admin-guide/kernel-parameters.txt index >>> b799bcf67d7b..9475f02c79da 100644 --- >>> a/Documentation/admin-guide/kernel-parameters.txt +++ >>> b/Documentation/admin-guide/kernel-parameters.txt @@ -1982,6 +1982,12 >>> @@ Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y, >>>               the default is off. >>>   +    kpti=        [ARM64] Control page table isolation of >>> user >>> +            and kernel address spaces. >>> +            Default: enabled on cores which need >>> mitigation. >> >> Would this be a good place to mention that we enable it when >> CONFIG_RANDOMIZE_BASE is enabled and we have a valid kaslr_offset? I >> found this somewhat surprising, also it's unrelated to the >> vulnerability. > > Maybe, but I tend to think since this command line forces it on/off > regardless of RANDOMIZE_BASE, that a better place to mention that > RANDOMIZE_BASE forces kpti on is the Kconfig option. True, kpti= takes precedence, in both ways. Disregard my comment then, this is indeed not the right place to mention RANDOMIZE_BASE. Cheers, Andre. > > BTW: Thanks for reviewing this. > > >> >> Cheers, >> Andre >> >>> +            0: force disabled >>> +            1: force enabled >>> + >>>       kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled >>> MSRs. Default is 0 (don't ignore, but inject #GP) >>>   >> >