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 C7F6BC43441 for ; Mon, 19 Nov 2018 13:52:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 932DF2086A for ; Mon, 19 Nov 2018 13:52:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 932DF2086A 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 S1729380AbeKTAPt (ORCPT ); Mon, 19 Nov 2018 19:15:49 -0500 Received: from Galois.linutronix.de ([146.0.238.70]:38554 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727310AbeKTAPt (ORCPT ); Mon, 19 Nov 2018 19:15:49 -0500 Received: from hsi-kbw-5-158-153-52.hsi19.kabel-badenwuerttemberg.de ([5.158.153.52] 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 1gOjxq-0007tm-DP; Mon, 19 Nov 2018 14:51:46 +0100 Date: Mon, 19 Nov 2018 14:51:45 +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 , LKML , x86@kernel.org, Willy Tarreau Subject: Re: [Patch v5 11/16] x86/speculation: Add Spectre v2 app to app protection modes 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 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 19 Nov 2018, Jiri Kosina wrote: > On Mon, 19 Nov 2018, Thomas Gleixner wrote: > > > > On Sat, 17 Nov 2018, Jiri Kosina wrote: > > > > > Subject: [PATCH] x86/speculation: enforce STIBP for SECCOMP tasks in lite mode > > > > > > If 'lite' mode of app2app protection from spectre_v2 is selected on > > > kernel command-line, we are currently applying STIBP protection to > > > non-dumpable tasks, and tasks that have explicitly requested such > > > protection via > > > > > > prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIR_BRANCH, PR_SPEC_ENABLE, 0, 0); > > > > > > Let's extend this to cover also SECCOMP tasks (analogically to how we > > > apply SSBD protection). > > > > Right. And SSBD does not fiddle with dumpable. > > > > Willy had concerns about the (ab)use of dumpable so I'm holding off on that > > bit for now. > > Yeah. IBPB implementation used to check the dumpability of tasks during > rescheduling, but that went away later. > > I still think that ideally that 'app2app' setting would toggle how IBPB is > being used as well, something along the lines: > > lite: > - STIBP for the ones marked via prctl() and SECCOMP with the TIF_ > flag > - ibpb_needed() returning true for the same > > strict: > - STIBP: as currently implemented > - ibpb_needed() returning always true > > off: > - neither STIBP nor IBPB applied ever > > That's give us also some % of performance lost via IBPB back. > > Makes sense? Except for the naming convention, yes. See other mail. Thanks, tglx