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 68394C47082 for ; Mon, 7 Jun 2021 13:36:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 475FF60BBB for ; Mon, 7 Jun 2021 13:36:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230256AbhFGNiq (ORCPT ); Mon, 7 Jun 2021 09:38:46 -0400 Received: from mga18.intel.com ([134.134.136.126]:27432 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230127AbhFGNip (ORCPT ); Mon, 7 Jun 2021 09:38:45 -0400 IronPort-SDR: M78Uuh8itRJIFK1ryhVLGdOjIJQ5O/gBP7LjYh5KF6JHb2VFZZ45PZs941Yq+ZnVwaXMwG10yM bCZMFOvzSW4w== X-IronPort-AV: E=McAfee;i="6200,9189,10008"; a="191949578" X-IronPort-AV: E=Sophos;i="5.83,255,1616482800"; d="scan'208";a="191949578" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Jun 2021 06:36:53 -0700 IronPort-SDR: /W9+aDYV4uMaEdr1mZOfXOm7Rfd9BjVLQwFrJiAMEPAHT4xxYEIqCXn4Eorea4kXMQQK/I2oit 5rX9ivU7H21A== X-IronPort-AV: E=Sophos;i="5.83,255,1616482800"; d="scan'208";a="481526543" Received: from mjkachma-mobl.amr.corp.intel.com (HELO [10.212.201.234]) ([10.212.201.234]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Jun 2021 06:36:52 -0700 Subject: Re: [patch V2 00/14] x86/fpu: Mop up XSAVES and related damage To: Thomas Gleixner , LKML Cc: x86@kernel.org, Andy Lutomirski , Dave Hansen , Fenghua Yu , Tony Luck , Yu-cheng Yu , Sebastian Andrzej Siewior References: <20210605234742.712464974@linutronix.de> <87h7i9zv3r.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: <87h7i9zv3r.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 6/7/21 6:02 AM, Thomas Gleixner wrote: > On Sun, Jun 06 2021 at 01:47, Thomas Gleixner wrote: >> P.S: I picked up Dave's PKRU series from > and while looking deeper at that I found the following existing > inconsistency vs. PKRU: > > On exec() the kernel sets PKRU to the default value which is as > restrictive as possible. > > But on sigrestore PKRU when the init optimization is used PKRU is reset > to the hardware default (0), which is as permissive as possible: > > 1) On XRSTOR from user and the signal handler cleared the PKRU feature > bit in xsave.header.xfeatures. That's true for the fast and the > slow path. > > 2) For the fx_only case which loads the init_fpstate (with my fixes > applied that's not longer the case) > > So that's inconsistent at best. > > As the kernel defines the "init" behaviour of PKRU as non-permissive > on exec() it should do so consequently in sigrestore as well. Agreed. The kernel has essentially picked its own init value for PKRU, separate from the hardware init value. It should be applied consistently. By the way, are you talking specifically about the _error_ paths where the kernel is unable to XRSTOR the signal XSAVE buffer for some reason, and tries to apply either init_fpu or the hardware init state instead?