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,URIBL_BLOCKED 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 E7E24C169C4 for ; Wed, 6 Feb 2019 19:24:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A5B532083B for ; Wed, 6 Feb 2019 19:24:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726994AbfBFTYZ (ORCPT ); Wed, 6 Feb 2019 14:24:25 -0500 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:57326 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726480AbfBFTYZ (ORCPT ); Wed, 6 Feb 2019 14:24:25 -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 3F8C680D; Wed, 6 Feb 2019 11:24:24 -0800 (PST) Received: from [192.168.100.241] (usa-sjc-mx-foss1.foss.arm.com [217.140.101.70]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 98CEB3F719; Wed, 6 Feb 2019 11:24:22 -0800 (PST) Subject: Re: [PATCH v4 01/12] Documentation: Document arm64 kpti control To: Andre Przywara 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> From: Jeremy Linton Message-ID: <69fceac6-7e83-7b38-44fb-2c02245f51df@arm.com> Date: Wed, 6 Feb 2019 13:24:17 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20190130180247.15ab0577@donnerap.cambridge.arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. 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) >> >