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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 A172FC48BE5 for ; Sat, 12 Jun 2021 00:40:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6EB1F611B0 for ; Sat, 12 Jun 2021 00:40:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230291AbhFLAmd (ORCPT ); Fri, 11 Jun 2021 20:42:33 -0400 Received: from mga06.intel.com ([134.134.136.31]:11854 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229584AbhFLAma (ORCPT ); Fri, 11 Jun 2021 20:42:30 -0400 IronPort-SDR: 820RkrKTtoszMjfF7zdC0LzJceEYdiFfM6Y8O5czkEphsv4DgMa6fhapT9GyvFB1oL2qGxLrmT P3VNveq8I/7w== X-IronPort-AV: E=McAfee;i="6200,9189,10012"; a="266783619" X-IronPort-AV: E=Sophos;i="5.83,267,1616482800"; d="scan'208";a="266783619" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Jun 2021 17:40:29 -0700 IronPort-SDR: JIGLFgtCK9gmwD95pa2xd0cHK/07qv/ZQndsyPC7/8nEExKksl2ptKNqoOp89P9R9anlOaG8k/ nFZN3RHhSslg== X-IronPort-AV: E=Sophos;i="5.83,267,1616482800"; d="scan'208";a="486783471" Received: from svkandu1-mobl1.amr.corp.intel.com (HELO [10.251.4.209]) ([10.251.4.209]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Jun 2021 17:40:28 -0700 Subject: Re: [patch 00/41] x86/fpu: Spring cleaning and PKRU sanitizing To: Thomas Gleixner , LKML Cc: Andy Lutomirski , Dave Hansen , Fenghua Yu , Tony Luck , Yu-cheng Yu , Sebastian Andrzej Siewior , Borislav Petkov , Peter Zijlstra , Kan Liang References: <20210611161523.508908024@linutronix.de> <871r98vsjy.ffs@nanos.tec.linutronix.de> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <871r98vsjy.ffs@nanos.tec.linutronix.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/11/21 5:24 PM, Thomas Gleixner wrote: > The Intel SDM states in volume 1, chapter 13.6 > > PROCESSOR TRACKING OF XSAVE-MANAGED STATE > > * PKRU state. PKRU state is in its initial configuration if the value > of the PKRU is 0.> ... > IOW there is no consistency vs. XINUSE and initial state guaranteed at > all. So why should the kernel worry about this? This is my feeling on it as well. I may be a bit corrupted by having talked to the hardware folks who have built the init state "trackers", but I've always had the opinion that XINUSE is very weakly defined. There are some other bits of the SDM that you noted that clearly call out that XINUSE is not strictly tied to the *value* of the component.