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=-20.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=unavailable 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 B78FEC4332B for ; Wed, 17 Feb 2021 13:18:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 89BE164E45 for ; Wed, 17 Feb 2021 13:18:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232864AbhBQNSZ (ORCPT ); Wed, 17 Feb 2021 08:18:25 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33088 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232533AbhBQNSO (ORCPT ); Wed, 17 Feb 2021 08:18:14 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 51D5FC061574; Wed, 17 Feb 2021 05:17:33 -0800 (PST) Date: Wed, 17 Feb 2021 13:17:30 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1613567851; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=qB4HogsaDhgqvLnS7LEaBAtHSECMrErbHEF0Mhacb7k=; b=R5ZbmKXoPv0twTUHq1ltVbMMIdlCyNwbPga8C7NGJwWoG+FBKEvdr3xyd+MoPu9lNYP6Gp 8S03g4eIT64SWxYzMalvcexlAEVWUta1Ta1CptUf3aLqUKLMCnRTAuxro0fxkQJCRDFXcY hlhf20F8MjT7JAe23FoMNluQXoOyFJith29oIxuSKFgdAtdJWqXTybjyzNoQXzta/5a0Cq jtyTpoNwNUncs/j/KursJHOVIG/ouiB0MGFX3lxJbsg1+z/0K/LX6BpENVwSiac6DGgJ+0 XwvlgqDTw5hovEXfo2vtrPrBwbr21yY/+cPwA9DDJ419GBmim5Fj2Af4MNuHeg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1613567851; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=qB4HogsaDhgqvLnS7LEaBAtHSECMrErbHEF0Mhacb7k=; b=8VqAQmUboHFhug4rraaYFsONg7/S8mbBEJryx9WpgEx+mTcW1uWApzsDAXOuhZr4G3mq8W ucmlu4TtEpF/YdAw== From: "tip-bot2 for Frederic Weisbecker" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] entry/kvm: Explicitly flush pending rcuog wakeup before last rescheduling point Cc: Peter Zijlstra , Frederic Weisbecker , Ingo Molnar , stable@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20210131230548.32970-6-frederic@kernel.org> References: <20210131230548.32970-6-frederic@kernel.org> MIME-Version: 1.0 Message-ID: <161356785079.20312.1441970262621353352.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/core branch of tip: Commit-ID: 4ae7dc97f726ea95c58ac58af71cc034ad22d7de Gitweb: https://git.kernel.org/tip/4ae7dc97f726ea95c58ac58af71cc034ad22d7de Author: Frederic Weisbecker AuthorDate: Mon, 01 Feb 2021 00:05:48 +01:00 Committer: Ingo Molnar CommitterDate: Wed, 17 Feb 2021 14:12:43 +01:00 entry/kvm: Explicitly flush pending rcuog wakeup before last rescheduling point Following the idle loop model, cleanly check for pending rcuog wakeup before the last rescheduling point upon resuming to guest mode. This way we can avoid to do it from rcu_user_enter() with the last resort self-IPI hack that enforces rescheduling. Suggested-by: Peter Zijlstra Signed-off-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20210131230548.32970-6-frederic@kernel.org --- arch/x86/kvm/x86.c | 1 +- include/linux/entry-kvm.h | 14 ++++++++++++- kernel/rcu/tree.c | 44 +++++++++++++++++++++++++++++--------- kernel/rcu/tree_plugin.h | 1 +- 4 files changed, 50 insertions(+), 10 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 1b404e4..b967c1c 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1782,6 +1782,7 @@ EXPORT_SYMBOL_GPL(kvm_emulate_wrmsr); bool kvm_vcpu_exit_request(struct kvm_vcpu *vcpu) { + xfer_to_guest_mode_prepare(); return vcpu->mode == EXITING_GUEST_MODE || kvm_request_pending(vcpu) || xfer_to_guest_mode_work_pending(); } diff --git a/include/linux/entry-kvm.h b/include/linux/entry-kvm.h index 9b93f85..8b2b1d6 100644 --- a/include/linux/entry-kvm.h +++ b/include/linux/entry-kvm.h @@ -47,6 +47,20 @@ static inline int arch_xfer_to_guest_mode_handle_work(struct kvm_vcpu *vcpu, int xfer_to_guest_mode_handle_work(struct kvm_vcpu *vcpu); /** + * xfer_to_guest_mode_prepare - Perform last minute preparation work that + * need to be handled while IRQs are disabled + * upon entering to guest. + * + * Has to be invoked with interrupts disabled before the last call + * to xfer_to_guest_mode_work_pending(). + */ +static inline void xfer_to_guest_mode_prepare(void) +{ + lockdep_assert_irqs_disabled(); + rcu_nocb_flush_deferred_wakeup(); +} + +/** * __xfer_to_guest_mode_work_pending - Check if work is pending * * Returns: True if work pending, False otherwise. diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 2ebc211..ce17b84 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -678,9 +678,10 @@ EXPORT_SYMBOL_GPL(rcu_idle_enter); #ifdef CONFIG_NO_HZ_FULL +#if !defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK) /* * An empty function that will trigger a reschedule on - * IRQ tail once IRQs get re-enabled on userspace resume. + * IRQ tail once IRQs get re-enabled on userspace/guest resume. */ static void late_wakeup_func(struct irq_work *work) { @@ -689,6 +690,37 @@ static void late_wakeup_func(struct irq_work *work) static DEFINE_PER_CPU(struct irq_work, late_wakeup_work) = IRQ_WORK_INIT(late_wakeup_func); +/* + * If either: + * + * 1) the task is about to enter in guest mode and $ARCH doesn't support KVM generic work + * 2) the task is about to enter in user mode and $ARCH doesn't support generic entry. + * + * In these cases the late RCU wake ups aren't supported in the resched loops and our + * last resort is to fire a local irq_work that will trigger a reschedule once IRQs + * get re-enabled again. + */ +noinstr static void rcu_irq_work_resched(void) +{ + struct rcu_data *rdp = this_cpu_ptr(&rcu_data); + + if (IS_ENABLED(CONFIG_GENERIC_ENTRY) && !(current->flags & PF_VCPU)) + return; + + if (IS_ENABLED(CONFIG_KVM_XFER_TO_GUEST_WORK) && (current->flags & PF_VCPU)) + return; + + instrumentation_begin(); + if (do_nocb_deferred_wakeup(rdp) && need_resched()) { + irq_work_queue(this_cpu_ptr(&late_wakeup_work)); + } + instrumentation_end(); +} + +#else +static inline void rcu_irq_work_resched(void) { } +#endif + /** * rcu_user_enter - inform RCU that we are resuming userspace. * @@ -702,8 +734,6 @@ static DEFINE_PER_CPU(struct irq_work, late_wakeup_work) = */ noinstr void rcu_user_enter(void) { - struct rcu_data *rdp = this_cpu_ptr(&rcu_data); - lockdep_assert_irqs_disabled(); /* @@ -711,13 +741,7 @@ noinstr void rcu_user_enter(void) * rescheduling opportunity in the entry code. Trigger a self IPI * that will fire and reschedule once we resume in user/guest mode. */ - instrumentation_begin(); - if (!IS_ENABLED(CONFIG_GENERIC_ENTRY) || (current->flags & PF_VCPU)) { - if (do_nocb_deferred_wakeup(rdp) && need_resched()) - irq_work_queue(this_cpu_ptr(&late_wakeup_work)); - } - instrumentation_end(); - + rcu_irq_work_resched(); rcu_eqs_enter(true); } diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 384856e..cdc1b76 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -2197,6 +2197,7 @@ void rcu_nocb_flush_deferred_wakeup(void) { do_nocb_deferred_wakeup(this_cpu_ptr(&rcu_data)); } +EXPORT_SYMBOL_GPL(rcu_nocb_flush_deferred_wakeup); void __init rcu_init_nohz(void) {