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=-0.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 053E2C28CBC for ; Thu, 7 May 2020 01:11:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DAEEC2075E for ; Thu, 7 May 2020 01:11:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728372AbgEGBLe (ORCPT ); Wed, 6 May 2020 21:11:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37850 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726807AbgEGBLe (ORCPT ); Wed, 6 May 2020 21:11:34 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D6545C061A0F for ; Wed, 6 May 2020 18:11:33 -0700 (PDT) Received: from p5de0bf0b.dip0.t-ipconnect.de ([93.224.191.11] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1jWV4Q-0007Ow-4G; Thu, 07 May 2020 03:11:26 +0200 Received: by nanos.tec.linutronix.de (Postfix, from userid 1000) id 8ECF7102652; Thu, 7 May 2020 03:11:25 +0200 (CEST) From: Thomas Gleixner To: Nelson D'Souza , bp@alien8.de Cc: mingo@redhat.com, x86@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, Tony Luck Subject: Re: [PATCH v1] x86/cpu/tsx: Change the TSX default from "off" to "auto" In-Reply-To: <20200506221459.29104-1-nelson.dsouza@linux.intel.com> References: <20200506221459.29104-1-nelson.dsouza@linux.intel.com> Date: Thu, 07 May 2020 03:11:25 +0200 Message-ID: <877dxok0qq.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Nelson D'Souza writes: > There are now several commercially available processors that have h/w > fixes for the TSX Async Abort (TAA) issue as indicated by enumerating > the ARCH_CAPABILITIES "TAA_NO" bit. > > Change the default setting to "auto" so that these CPUs will leave > TSX enabled by default. You are telling WHAT the patch does, but not the WHY. It's completely uninteresting whether TAA is fixed in a particular CPU simply because: 1) TAA is only one particular issue of TSX. 2) The main use case for TSX is to accelerate all sorts of speculation attacks and other malignances 3) There is excatly ONE known use case which cares about TSX and we already discussed to death that the machines on which that use case runs have admins which are capable of adding tsx=on on the command line. So unless you come up with some really convincing argument why this should be changed, this is not going to happen. Thanks, tglx