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=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 6DAE3C43441 for ; Mon, 19 Nov 2018 13:49:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3F17A20831 for ; Mon, 19 Nov 2018 13:49:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3F17A20831 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org 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 S1729437AbeKTANV (ORCPT ); Mon, 19 Nov 2018 19:13:21 -0500 Received: from mx2.suse.de ([195.135.220.15]:50128 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727310AbeKTANV (ORCPT ); Mon, 19 Nov 2018 19:13:21 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id C3C91AF04; Mon, 19 Nov 2018 13:49:38 +0000 (UTC) Date: Mon, 19 Nov 2018 14:49:36 +0100 (CET) From: Jiri Kosina To: Thomas Gleixner 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 (LSU 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, 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? Thanks, -- Jiri Kosina SUSE Labs