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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT 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 29EB9C433E1 for ; Tue, 19 May 2020 21:48:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0282C205CB for ; Tue, 19 May 2020 21:48:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728610AbgESVsG (ORCPT ); Tue, 19 May 2020 17:48:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41062 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728593AbgESVsB (ORCPT ); Tue, 19 May 2020 17:48:01 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 546CAC08C5C2; Tue, 19 May 2020 14:48:01 -0700 (PDT) Received: from [5.158.153.53] (helo=debian-buster-darwi.lab.linutronix.de.) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.80) (envelope-from ) id 1jbA5W-0002yb-3S; Tue, 19 May 2020 23:47:50 +0200 From: "Ahmed S. Darwish" To: Peter Zijlstra , Ingo Molnar , Will Deacon Cc: Thomas Gleixner , "Paul E. McKenney" , "Sebastian A. Siewior" , Steven Rostedt , LKML , "Ahmed S. Darwish" , Paolo Bonzini , kvm@vger.kernel.org Subject: [PATCH v1 24/25] kvm/eventfd: Use sequence counter with associated spinlock Date: Tue, 19 May 2020 23:45:46 +0200 Message-Id: <20200519214547.352050-25-a.darwish@linutronix.de> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200519214547.352050-1-a.darwish@linutronix.de> References: <20200519214547.352050-1-a.darwish@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 A sequence counter write side critical section must be protected by some form of locking to serialize writers. A plain seqcount_t does not contain the information of which lock must be held when entering a write side critical section. Use the new seqcount_spinlock_t data type, which allows to associate a spinlock with the sequence counter. This enables lockdep to verify that the spinlock used for writer serialization is held when the write side critical section is entered. If lockdep is disabled this lock association is compiled out and has neither storage size nor runtime overhead. Signed-off-by: Ahmed S. Darwish --- include/linux/kvm_irqfd.h | 2 +- virt/kvm/eventfd.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/kvm_irqfd.h b/include/linux/kvm_irqfd.h index dc1da020305b..dac047abdba7 100644 --- a/include/linux/kvm_irqfd.h +++ b/include/linux/kvm_irqfd.h @@ -42,7 +42,7 @@ struct kvm_kernel_irqfd { wait_queue_entry_t wait; /* Update side is protected by irqfds.lock */ struct kvm_kernel_irq_routing_entry irq_entry; - seqcount_t irq_entry_sc; + seqcount_spinlock_t irq_entry_sc; /* Used for level IRQ fast-path */ int gsi; struct work_struct inject; diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c index 67b6fc153e9c..8694a2920ea9 100644 --- a/virt/kvm/eventfd.c +++ b/virt/kvm/eventfd.c @@ -303,7 +303,7 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args) INIT_LIST_HEAD(&irqfd->list); INIT_WORK(&irqfd->inject, irqfd_inject); INIT_WORK(&irqfd->shutdown, irqfd_shutdown); - seqcount_init(&irqfd->irq_entry_sc); + seqcount_spinlock_init(&irqfd->irq_entry_sc, &kvm->irqfds.lock); f = fdget(args->fd); if (!f.file) { -- 2.20.1