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 656EEC43441 for ; Mon, 19 Nov 2018 19:03:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3732A20851 for ; Mon, 19 Nov 2018 19:03:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3732A20851 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 S1726629AbeKTF2U (ORCPT ); Tue, 20 Nov 2018 00:28:20 -0500 Received: from Galois.linutronix.de ([146.0.238.70]:39530 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725987AbeKTF2T (ORCPT ); Tue, 20 Nov 2018 00:28:19 -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 1gOop5-0001PT-8K; Mon, 19 Nov 2018 20:03:03 +0100 Date: Mon, 19 Nov 2018 20:03:02 +0100 (CET) From: Thomas Gleixner To: Tim Chen cc: Peter Zijlstra , Jiri Kosina , Tom Lendacky , Ingo Molnar , 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 08/16] smt: Create cpu_smt_enabled static key for SMT specific code In-Reply-To: <439a2d72-988c-d397-dc32-daf098af655c@linux.intel.com> Message-ID: References: <91b719e53640f60666b40a3516da2b80703b2f76.1542418937.git.tim.c.chen@linux.intel.com> <20181119145754.GA2131@hirez.programming.kicks-ass.net> <439a2d72-988c-d397-dc32-daf098af655c@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 Tim, On Mon, 19 Nov 2018, Tim Chen wrote: > On 11/19/2018 06:57 AM, Peter Zijlstra wrote: > > In particular, the SMT topology bits are set before we enable > > interrrupts and similarly, are cleared after we disable interrupts for > > the last time and die. > > > Peter & Thomas, > > Any objection if I export sched_smt_present after including > Peter's patch and use it in spec_ctrl_update_msr instead. > > Something like this? > > +#ifdef CONFIG_SCHED_SMT > + > +extern struct static_key_false sched_smt_present; > + > +static inline bool cpu_smt_present(void) > +{ > + if (static_branch_unlikely(&sched_smt_present)) > + return true; > + else > + return false; What's wrong with return static_branch_unlikely(&sched_smt_present); ??? But that's just a stylistic nitpick. The real issue is that you prevent the mitigation when CONFIG_SCHED_SMT=n. Thanks, tglx