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=-7.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 31F5EC83013 for ; Tue, 1 Dec 2020 15:38:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C8B9E2080A for ; Tue, 1 Dec 2020 15:38:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="1fAgPVa8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390252AbgLAPiK (ORCPT ); Tue, 1 Dec 2020 10:38:10 -0500 Received: from mail.kernel.org ([198.145.29.99]:49656 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388069AbgLAPiK (ORCPT ); Tue, 1 Dec 2020 10:38:10 -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 F1D512080A; Tue, 1 Dec 2020 15:37:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1606837049; bh=W4oSw5pqPg7HSVD+Y7fKRaIcd0puZHiqkYGcP7sRgQc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=1fAgPVa8GfZSVejj8sHJvSwqNUOe0hyoyqoyEKjZyszMEvs4LHxIwxHc9r6KIH1Qo xpl6TFrFCUM2NQDK5IJzr4fQ1hQHMk6Yo1AkZsf+Ax1H5gFLbeqz32DudQHh1AhoX9 wsQ7nLAG3D7lNsCxlh9Jz3tRuWaAq0+4N6+Hn2Ac= 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 1kk7iY-00F5UN-I1; Tue, 01 Dec 2020 15:37:26 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Date: Tue, 01 Dec 2020 15:37:26 +0000 From: Marc Zyngier To: wangrongwei Cc: catalin.marinas@arm.com, Will Deacon , bjorn.andersson@linaro.org, shawnguo@kernel.org, gshan@redhat.com, geert+renesas@glider.be, Anson.Huang@nxp.com, masahiroy@kernel.org, michael@walle.cc, krzk@kernel.org, linux-kernel@vger.kernel.org, vkoul@kernel.org, olof@lixom.net, vincenzo.frascino@arm.com, ardb@kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 0/3] arm64:msr: Add MSR driver In-Reply-To: <6FA68A07-F718-46F5-81B4-586A5ED3E479@linux.alibaba.com> References: <20201130174833.41315-1-rongwei.wang@linux.alibaba.com> <5e7f7225982b2df63e62ea60ec632376@misterjones.org> <855BA92C-5B22-4F14-965A-B1F72A872B8D@linux.alibaba.com> <059ed4a8768ff3881005796cb4a10d5e@kernel.org> <6FA68A07-F718-46F5-81B4-586A5ED3E479@linux.alibaba.com> User-Agent: Roundcube Webmail/1.4.9 Message-ID: <7e9ae04f3394a85aa3b8fe8947a44009@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: rongwei.wang@linux.alibaba.com, catalin.marinas@arm.com, will@kernel.org, bjorn.andersson@linaro.org, shawnguo@kernel.org, gshan@redhat.com, geert+renesas@glider.be, Anson.Huang@nxp.com, masahiroy@kernel.org, michael@walle.cc, krzk@kernel.org, linux-kernel@vger.kernel.org, vkoul@kernel.org, olof@lixom.net, vincenzo.frascino@arm.com, ardb@kernel.org, linux-arm-kernel@lists.infradead.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-kernel@vger.kernel.org On 2020-12-01 14:25, wangrongwei wrote: >> 2020年12月1日 下午4:12，Marc Zyngier 写道： >> >> On 2020-12-01 03:09, wangrongwei wrote: >>> Hi >>> We have validate this driver in vm and physical machine, and works >>> fine. >> >> But what does "work fine" mean? None of these system registers are >> supposed >> to be accessible from userspace, so please explain *what* you are >> trying to >> do with this, other that introducing security holes and general system >> instability? > I think I know what you mean. Do you want me to describe how we > achieved it? > In x86, the different registers can be accessed directly using the > rdmsr and wrmsr instructions, but in ARM, since these two instructions > are missing, so we modify the code segment during runtime, similar to > the principle of static_key. [...] These are implementation details, none of which answer my question: What makes you think this is a good idea? I cannot see any legitimate reason for userspace to ever access privileged system registers, and the fact that x86 has such feature isn't a good justification. M. -- Jazz is not dead. It just smells funny...