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=-8.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,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 3DD8BC63697 for ; Wed, 18 Nov 2020 08:59:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E0508241A5 for ; Wed, 18 Nov 2020 08:59:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727291AbgKRI6x (ORCPT ); Wed, 18 Nov 2020 03:58:53 -0500 Received: from relay5-d.mail.gandi.net ([217.70.183.197]:33679 "EHLO relay5-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725772AbgKRI6x (ORCPT ); Wed, 18 Nov 2020 03:58:53 -0500 X-Greylist: delayed 43111 seconds by postgrey-1.27 at vger.kernel.org; Wed, 18 Nov 2020 03:58:52 EST X-Originating-IP: 62.210.143.248 Received: from weirdfishes.localdomain (62-210-143-248.rev.poneytelecom.eu [62.210.143.248]) (Authenticated sender: m@thi.eu.com) by relay5-d.mail.gandi.net (Postfix) with ESMTPSA id B6C241C0009; Wed, 18 Nov 2020 08:58:49 +0000 (UTC) Received: by weirdfishes.localdomain (Postfix, from userid 1000) id 5DF1372214948; Wed, 18 Nov 2020 09:58:49 +0100 (CET) Date: Wed, 18 Nov 2020 09:58:49 +0100 From: Mathieu Chouquet-Stringer To: Borislav Petkov Cc: Matthew Garrett , Chris Down , Linux Kernel Mailing List , sean.j.christopherson@intel.com, tony.luck@intel.com, Linus Torvalds , the arch/x86 maintainers , kernel-team@fb.com Subject: Re: [PATCH -v2.1] x86/msr: Filter MSR writes Message-ID: <20201118085849.GA189743@weirdfishes> Mail-Followup-To: Mathieu Chouquet-Stringer , Borislav Petkov , Matthew Garrett , Chris Down , Linux Kernel Mailing List , sean.j.christopherson@intel.com, tony.luck@intel.com, Linus Torvalds , the arch/x86 maintainers , kernel-team@fb.com References: <20200615063837.GA14668@zn.tnic> <20200714121955.GA2080@chrisdown.name> <20200714154728.GA3101@nazgul.tnic> <20200714160448.GC2080@chrisdown.name> <20201117210018.GA4247@weirdfishes> <20201117212016.GQ5719@zn.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201117212016.GQ5719@zn.tnic> X-Face: %JOeya=Dg!}[/#Go&*&cQ+)){p1c8}u\Fg2Q3&)kothIq|JnWoVzJtCFo~4X X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 17, 2020 at 10:20:16PM +0100, Borislav Petkov wrote: > Not for long: > > https://git.kernel.org/tip/fe0a5788624c8b8f113a35bbe4636e37f9321241 That's fantastic. > Because if you poke at random MSRs and you manage to "configure" your > CPU to run "out of spec" - this is what the taint flag is called: > TAINT_CPU_OUT_OF_SPEC - then this is exactly the case you've created: a > CPU executing outside of specifications. Don't get me wrong, it makes total sense to do that, it's just the original reason of !SMP-capable isn't so clear while CPU out of spec is. -- Mathieu Chouquet-Stringer me@mathieu.digital The sun itself sees not till heaven clears. -- William Shakespeare --