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=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 A4836C5517A for ; Wed, 11 Nov 2020 21:10:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3C30020665 for ; Wed, 11 Nov 2020 21:10:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="nDLR80BG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726632AbgKKVKp (ORCPT ); Wed, 11 Nov 2020 16:10:45 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40266 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725933AbgKKVKm (ORCPT ); Wed, 11 Nov 2020 16:10:42 -0500 Received: from mail-qk1-x742.google.com (mail-qk1-x742.google.com [IPv6:2607:f8b0:4864:20::742]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 71185C0613D1 for ; Wed, 11 Nov 2020 13:10:42 -0800 (PST) Received: by mail-qk1-x742.google.com with SMTP id 11so3225687qkd.5 for ; Wed, 11 Nov 2020 13:10:42 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=nShzfx2jlTbPvWjrgA0qLkMImP/KRoOb/9o5edtvwT8=; b=nDLR80BGlpKLsXqsNfvL8BgzidSKLF7NNA2lb3/wrH1jDq233HtOJptNkV90Zn0800 eR0Fxyu7k/MrU7JAU0Pf2W9DNjC3BVEo3KvLI657/53xPFw1I/ry2rgmSQ6/vFcw7fFz FEi1KL9USJ7m0r/qIAt6T92kbtSx87nZ+i5jk= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=nShzfx2jlTbPvWjrgA0qLkMImP/KRoOb/9o5edtvwT8=; b=ISlSLmHOmQsaavxUS2clrQ/a3YNduuVV3gKKXww7sljLcmMnM5374GCmgM/H/Vsqf0 KTDjOmPxUu6dDUS1mrQzcvmNfl1MOs6SXs380FlzRAMezRbqaWmSf2XLTvZrwKGXrovB RkaFw6mnkc/pbpkW/4tCpAoYU3vlWp05RsEjGBvK9cbo1T7vM+AlXe0H8HWA8IEF6otw G+g4EajIAV2dG8lRKvB6TBM0c0VlCUZu9racYgNkElDAE5kOblr8+wpw2zD9hoPeL8wt PxpU8S212zJi3fOuFpAdsuintP/5OLCDvLOwZ0YqyLxT270IbSXCMpMyOi4X/jl6j+N2 YSMw== X-Gm-Message-State: AOAM532Lj0Xk92cnQyuWbt+EHiINtkaljcoUAfJ+FL/2zpi2uA8ddTmN rHqCK3nHZ8A75BLpBjLduzOLbQ== X-Google-Smtp-Source: ABdhPJz2OspMfh8UZUv7C1WmKn2rxqDZ25+pqHfshZMlU6B6YcsIeYzBy3irANcsZRlRB45jBmlZAw== X-Received: by 2002:a05:620a:7ea:: with SMTP id k10mr25335758qkk.292.1605129041688; Wed, 11 Nov 2020 13:10:41 -0800 (PST) Received: from joelaf.cam.corp.google.com ([2620:15c:6:411:cad3:ffff:feb3:bd59]) by smtp.gmail.com with ESMTPSA id d66sm2112389qke.132.2020.11.11.13.10.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Nov 2020 13:10:41 -0800 (PST) From: "Joel Fernandes (Google)" To: Nishanth Aravamudan , Julien Desfossez , Peter Zijlstra , Tim Chen , Vineeth Pillai , Aaron Lu , Aubrey Li , tglx@linutronix.de, linux-kernel@vger.kernel.org Cc: mingo@kernel.org, torvalds@linux-foundation.org, fweisbec@gmail.com, keescook@chromium.org, kerrnel@google.com, Phil Auld , Valentin Schneider , Mel Gorman , Pawan Gupta , Paolo Bonzini , joel@joelfernandes.org, vineeth@bitbyteword.org, Chen Yu , Christian Brauner , Agata Gruza , Antonio Gomez Iglesias , graf@amazon.com, konrad.wilk@oracle.com, dfaggioli@suse.com, pjt@google.com, rostedt@goodmis.org, derkling@google.com, benbjiang@tencent.com, Alexandre Chartre , James.Bottomley@hansenpartnership.com, OWeisse@umich.edu, Dhaval Giani , Junaid Shahid , jsbarnes@google.com, chris.hyser@oracle.com, Ben Segall , Josh Don , Hao Luo , amistry@google.com, Borislav Petkov , Daniel Bristot de Oliveira , Dietmar Eggemann , "H. Peter Anvin" , Ingo Molnar , Juri Lelli , Mel Gorman , Mike Rapoport , thomas.lendacky@amd.com, Tony Luck , Vincent Guittot , x86@kernel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)) Subject: [RFC 1/2] x86/bugs: Disable coresched on hardware that does not need it Date: Wed, 11 Nov 2020 16:10:10 -0500 Message-Id: <20201111211011.1381848-2-joel@joelfernandes.org> X-Mailer: git-send-email 2.29.2.222.g5d2a92d10f8-goog In-Reply-To: <20201111211011.1381848-1-joel@joelfernandes.org> References: <20201111211011.1381848-1-joel@joelfernandes.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Some hardware such as certain AMD variants don't have cross-HT MDS/L1TF issues. Detect this and don't enable core scheduling as it can needlessly slow the device done. Signed-off-by: Joel Fernandes (Google) --- arch/x86/kernel/cpu/bugs.c | 8 ++++++++ kernel/sched/core.c | 7 +++++++ kernel/sched/sched.h | 5 +++++ 3 files changed, 20 insertions(+) diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index dece79e4d1e9..0e6e61e49b23 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -152,6 +152,14 @@ void __init check_bugs(void) #endif } +/* + * Do not need core scheduling if CPU does not have MDS/L1TF vulnerability. + */ +int arch_allow_core_sched(void) +{ + return boot_cpu_has_bug(X86_BUG_MDS) || boot_cpu_has_bug(X86_BUG_L1TF); +} + void x86_virt_spec_ctrl(u64 guest_spec_ctrl, u64 guest_virt_spec_ctrl, bool setguest) { diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 64c559192634..c6158b4959fe 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -319,6 +319,13 @@ static void __sched_core_enable(void) for_each_online_cpu(cpu) BUG_ON(!sched_core_empty(cpu_rq(cpu))); + /* + * Some architectures may not want coresched. (ex, AMD does not have + * MDS/L1TF issues so it wants SMT completely on). + */ + if (!arch_allow_core_sched()) + return; + static_branch_enable(&__sched_core_enabled); stop_machine(__sched_core_stopper, (void *)true, NULL); diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 3cf08c77b678..a1b39764a6ed 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1203,6 +1203,11 @@ int cpu_core_tag_color_write_u64(struct cgroup_subsys_state *css, bool cfs_prio_less(struct task_struct *a, struct task_struct *b, bool fi); +int __weak arch_allow_core_sched(void) +{ + return true; +} + #else /* !CONFIG_SCHED_CORE */ static inline bool sched_core_enqueued(struct task_struct *task) { return false; } -- 2.29.2.222.g5d2a92d10f8-goog