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=-1.0 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 7BB3CC43441 for ; Tue, 20 Nov 2018 00:00:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3B701208E3 for ; Tue, 20 Nov 2018 00:00:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3B701208E3 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 S1732215AbeKTK0s (ORCPT ); Tue, 20 Nov 2018 05:26:48 -0500 Received: from Galois.linutronix.de ([146.0.238.70]:40060 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731651AbeKTK0s (ORCPT ); Tue, 20 Nov 2018 05:26:48 -0500 Received: from p4fea46ac.dip0.t-ipconnect.de ([79.234.70.172] helo=nanos) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1gOtSk-00068x-T2; Tue, 20 Nov 2018 01:00:19 +0100 Date: Tue, 20 Nov 2018 01:00:18 +0100 (CET) From: Thomas Gleixner To: Jiri Kosina cc: Tim Chen , Tom Lendacky , Ingo Molnar , Peter Zijlstra , Josh Poimboeuf , Andrea Arcangeli , David Woodhouse , Andi Kleen , Dave Hansen , Casey Schaufler , Asit Mallick , Arjan van de Ven , Jon Masters , Waiman Long , linux-kernel@vger.kernel.org, x86@kernel.org Subject: Re: [Patch v5 11/16] x86/speculation: Add Spectre v2 app to app protection modes In-Reply-To: Message-ID: References: <49d27ed3-dc44-042c-4941-31dedb2a56d2@linux.intel.com> 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, 20 Nov 2018, Jiri Kosina wrote: > On Tue, 20 Nov 2018, Thomas Gleixner wrote: > > > What? IBPB makes tons of sense even without STIBP. > > On non-SMT, yes. But this patchset ties those two the other (sensible) way > around AFAICS ("STIBP iff (IBPB && SMT)"). Errm. No. The patches disable IBPB if STIBP is not available and that has absolutely nothing to do with SMT simply because the static key controlling IBPB is only flipped on when both IBPB and STIBP are available. For SMT=off STIBP is pointless, but IBPB still makes a lot of sense. That's a change which is neither documented nor correct. Thanks, tglx