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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,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 1B738C43441 for ; Mon, 19 Nov 2018 18:08:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CE03E2086A for ; Mon, 19 Nov 2018 18:08:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CE03E2086A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com 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 S1730747AbeKTEdb (ORCPT ); Mon, 19 Nov 2018 23:33:31 -0500 Received: from mga07.intel.com ([134.134.136.100]:59792 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730192AbeKTEda (ORCPT ); Mon, 19 Nov 2018 23:33:30 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 19 Nov 2018 10:08:53 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,253,1539673200"; d="scan'208";a="109839538" Received: from schen9-desk.jf.intel.com (HELO [10.54.74.144]) ([10.54.74.144]) by orsmga002.jf.intel.com with ESMTP; 19 Nov 2018 10:08:53 -0800 To: Peter Zijlstra Cc: Jiri Kosina , Thomas Gleixner , 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 References: <91b719e53640f60666b40a3516da2b80703b2f76.1542418937.git.tim.c.chen@linux.intel.com> <20181119145754.GA2131@hirez.programming.kicks-ass.net> From: Tim Chen Openpgp: preference=signencrypt Autocrypt: addr=tim.c.chen@linux.intel.com; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.0 MIME-Version: 1.0 In-Reply-To: <20181119145754.GA2131@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/19/2018 06:57 AM, Peter Zijlstra wrote: > On Fri, Nov 16, 2018 at 05:53:51PM -0800, Tim Chen wrote: >> In later code, STIBP will be turned on/off in the context switch code >> path when SMT is enabled. Checks for SMT is best >> avoided on such hot paths. >> >> Create cpu_smt_enabled static key to turn on such SMT specific code >> statically. > > AFAICT this patch only follows the SMT control knob but not the actual > topology state. > > And, as I previously wrote, we already have sched_smt_present, which is > supposed to do much the same. > > All you need is the below to make it accurately track the topology. > > --- > Subject: sched/smt: Make sched_smt_present track topology > > Currently the sched_smt_present static key is only enabled when we > encounter SMT topology. However there is demand to also disable the key > when the topology changes such that there is no SMT present anymore. > > Implement this by making the key count the number of cores that have SMT > enabled. > > 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? Tim diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 943e90d..62fc3af 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -410,8 +410,7 @@ static __always_inline void spec_ctrl_update_msr(unsigned long tifn) * Need STIBP defense against Spectre v2 attack * if SMT is in use and enhanced IBRS is unsupported. */ - if (static_branch_likely(&cpu_smt_enabled) && - !static_cpu_has(X86_FEATURE_USE_IBRS_ENHANCED)) + if (cpu_smt_present() && !static_cpu_has(X86_FEATURE_USE_IBRS_ENHANCED)) msr |= stibp_tif_to_spec_ctrl(tifn); wrmsrl(MSR_IA32_SPEC_CTRL, msr); diff --git a/include/linux/cpu.h b/include/linux/cpu.h index 3d90155..e3d985e 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -68,6 +68,27 @@ struct device *cpu_device_create(struct device *parent, void *drvdata, extern ssize_t arch_cpu_release(const char *, size_t); #endif +#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; +} + +#else + +static inline bool cpu_smt_present(void) +{ + return false; +} + +#endif + /* * These states are not related to the core CPU hotplug mechanism. They are * used by various (sub)architectures to track internal state diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 618577f..e1e3f09 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -937,8 +937,6 @@ static inline int cpu_of(struct rq *rq) #ifdef CONFIG_SCHED_SMT -extern struct static_key_false sched_smt_present; - extern void __update_idle_core(struct rq *rq); static inline void update_idle_core(struct rq *rq)