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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,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 9D5A1C63777 for ; Mon, 30 Nov 2020 19:04:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 35DAC20789 for ; Mon, 30 Nov 2020 19:04:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="jrCIk71I" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388239AbgK3TEQ (ORCPT ); Mon, 30 Nov 2020 14:04:16 -0500 Received: from mail.skyhub.de ([5.9.137.197]:41966 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387684AbgK3TEP (ORCPT ); Mon, 30 Nov 2020 14:04:15 -0500 Received: from zn.tnic (p200300ec2f0c0400247ce5eea000f6a3.dip0.t-ipconnect.de [IPv6:2003:ec:2f0c:400:247c:e5ee:a000:f6a3]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 61A701EC04A9; Mon, 30 Nov 2020 20:03:34 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1606763014; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=rOUJuYK9wa/A/SuFfQYy/ZZkyjuXFeT8MrvwplFTrug=; b=jrCIk71InAWgGv6MbKCP/PFkK+mFlCMD6mvNGDXGXBjva/yHKnrkiSrGICWiapeoO0tSSp boZw16x4ifvlxt7leKkJr6pVUlJlOa3knq3QcEFk9Kh0RdTWee4gd76h/IgS11F7RWPW3w 8cJNDcBF2o3fMatncsMx1sRdnvBwnx4= Date: Mon, 30 Nov 2020 20:03:31 +0100 From: Borislav Petkov To: Rongwei Wang Cc: catalin.marinas@arm.com, will@kernel.org, bjorn.andersson@linaro.org, shawnguo@kernel.org, vkoul@kernel.org, geert+renesas@glider.be, Anson.Huang@nxp.com, michael@walle.cc, krzk@kernel.org, olof@lixom.net, vincenzo.frascino@arm.com, ardb@kernel.org, masahiroy@kernel.org, gshan@redhat.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/3] arm64:msr: Add MSR driver Message-ID: <20201130190331.GI6019@zn.tnic> References: <20201130174833.41315-1-rongwei.wang@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20201130174833.41315-1-rongwei.wang@linux.alibaba.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 01, 2020 at 01:48:30AM +0800, Rongwei Wang wrote: > MSR ARM driver aims to provide interfacs for user to read or write > data to all system registers. Just a warranty from x86 land: if I were an ARM arch maintainer, I would never never *ever* take such driver exposing naked hw registers to userspace. We have been fighting with this on x86 for years: a7e1f67ed29f ("x86/msr: Filter MSR writes") with userspace tools poking at random MSRs. Read the commit message for what can happen. And taking that thing is like opening a huge can'o'worms that can't be closed anymore. Currently, we're trying to move userspace tools to proper sysfs interfaces but it is a huuuge pain. It is a lot easier to have people define proper interfaces from the get-go where the kernel can control and synchronize access. HTH. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette