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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 24C89C04ABB for ; Tue, 11 Sep 2018 21:46:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BF8FC2086A for ; Tue, 11 Sep 2018 21:46:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BF8FC2086A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linutronix.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728161AbeILCre (ORCPT ); Tue, 11 Sep 2018 22:47:34 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:42486 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727775AbeILCre (ORCPT ); Tue, 11 Sep 2018 22:47:34 -0400 Received: from p4fea45ac.dip0.t-ipconnect.de ([79.234.69.172] helo=nanos) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1fzqTz-0006ZI-8v; Tue, 11 Sep 2018 23:46:03 +0200 Date: Tue, 11 Sep 2018 23:46:02 +0200 (CEST) From: Thomas Gleixner To: Tim Chen cc: Jiri Kosina , Ingo Molnar , Peter Zijlstra , Josh Poimboeuf , Andrea Arcangeli , "Woodhouse, David" , Andi Kleen , "Schaufler, Casey" , linux-kernel@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH v5 2/2] x86/speculation: Enable cross-hyperthread spectre v2 STIBP mitigation In-Reply-To: Message-ID: References: User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII 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 On Tue, 11 Sep 2018, Thomas Gleixner wrote: > On Tue, 11 Sep 2018, Tim Chen wrote: > > On 09/10/2018 04:46 AM, Jiri Kosina wrote: > > > Nah, IBPB is actuall there, sorry. So I'll add reporting of STIBP + fixup > > > the missing reporting of RSB_CTXSW for v6. > > > > > > > I anticipate that STIBP could affect workloads with a lot of indirect > > branches (see previous discussion with Andrea). We should have a > > knob for people to opt in or opt out of STIBP. > > Feel free to send a patch to that effect. Along with a proper explanation why it makes sense to disable this particular piece separate from the rest of the V2 mitigations. You surely can come up with a rationale based on facts rather than on anticipations. Thanks, tglx