From patchwork Wed Jul 11 18:01:01 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Woodhouse X-Patchwork-Id: 10520265 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 1209B603D7 for ; Wed, 11 Jul 2018 18:01:18 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 058DC29677 for ; Wed, 11 Jul 2018 18:01:18 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id EE00C2967F; Wed, 11 Jul 2018 18:01:17 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI, T_DKIM_INVALID autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 97E5629677 for ; Wed, 11 Jul 2018 18:01:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389200AbeGKSGd (ORCPT ); Wed, 11 Jul 2018 14:06:33 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:54786 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388829AbeGKSGd (ORCPT ); Wed, 11 Jul 2018 14:06:33 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=Sender:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Cc:MIME-Version:Content-Type: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=xU8xnt5z0i0cOwf5Oj2C7sEJ0zxv39qS3yuH5uF96TI=; b=WqGspgUPM3PEnscGmH0xgxfNP CWyyNEL3TwGB17eNZlDKDoyGLD/oG7GBXohC7F/P5wH8jlKpnOnyLPtJ4znEbNV2iyfR+3uf7r1Kl sm4CW1NXb4Vm4cwHnBVL+hQWjpsE+41QhnIM8y4MYP60xeA2dY4TuX9l3UhSG3yuUbZwfoIRX5YrQ NMy/VxRf+a4eNivPYtpjLEBMK/tsVpPTt3m4mv8xwhtB0Noiqhxr2YYTi82YppcRdKfZ+hnOMT/Qt FLG3XK0tF+CMyY4bGFWLb77Fv/ra5kgd7xLqGwyvlfC5ONGEAsA2pDcFgDMKWpI0gJiMzaVIAcomP C+Md08Hzw==; Received: from [2001:8b0:10b:1::425] (helo=i7.infradead.org) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1fdJQF-0005Ga-5z; Wed, 11 Jul 2018 18:01:03 +0000 Received: from dwoodhou by i7.infradead.org with local (Exim 4.91 #2 (Red Hat Linux)) id 1fdJQD-00FZXD-Mg; Wed, 11 Jul 2018 19:01:01 +0100 From: David Woodhouse To: peterz@infradead.org, mhillenb@amazon.de, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, paulmck@linux.vnet.ibm.com Subject: [PATCH v2] kvm/x86: Inform RCU of quiescent state when entering guest mode Date: Wed, 11 Jul 2018 19:01:01 +0100 Message-Id: <20180711180101.3711464-1-dwmw2@infradead.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20180711174843.GX3593@linux.vnet.ibm.com> References: <20180711174843.GX3593@linux.vnet.ibm.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: David Woodhouse RCU can spend long periods of time waiting for a CPU which is actually in KVM guest mode, entirely pointlessly. Treat it like the idle and userspace modes, and don't wait for it. Signed-off-by: David Woodhouse --- arch/x86/kvm/x86.c | 2 ++ include/linux/rcupdate.h | 7 +++++++ kernel/rcu/tree.c | 2 ++ 3 files changed, 11 insertions(+) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 0046aa70205a..b0c82f70afa7 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -7458,7 +7458,9 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) vcpu->arch.switch_db_regs &= ~KVM_DEBUGREG_RELOAD; } + rcu_kvm_enter(); kvm_x86_ops->run(vcpu); + rcu_kvm_exit(); /* * Do this here before restoring debug registers on the host. And diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 65163aa0bb04..1325f9d9ce00 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -212,6 +212,13 @@ do { \ #error "Unknown RCU implementation specified to kernel configuration" #endif +/* + * These are currently identical to the _idle_ versions but let's + * explicitly have separate copies to keep Paul honest in future. + */ +static inline void rcu_kvm_enter(void) { rcu_idle_enter(); } +static inline void rcu_kvm_exit(void) { rcu_idle_exit(); } + /* * The init_rcu_head_on_stack() and destroy_rcu_head_on_stack() calls * are needed for dynamic initialization and destruction of rcu_head diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index aa7cade1b9f3..d38c381bf4e3 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -760,6 +760,7 @@ void rcu_idle_enter(void) lockdep_assert_irqs_disabled(); rcu_eqs_enter(false); } +EXPORT_SYMBOL_GPL(rcu_idle_enter); #ifdef CONFIG_NO_HZ_FULL /** @@ -913,6 +914,7 @@ void rcu_idle_exit(void) rcu_eqs_exit(false); local_irq_restore(flags); } +EXPORT_SYMBOL_GPL(rcu_idle_exit); #ifdef CONFIG_NO_HZ_FULL /**