From patchwork Thu Jan 27 06:54:49 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hou Wenlong X-Patchwork-Id: 12726334 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 71FECC433EF for ; Thu, 27 Jan 2022 06:54:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231415AbiA0Gyw (ORCPT ); Thu, 27 Jan 2022 01:54:52 -0500 Received: from out0-136.mail.aliyun.com ([140.205.0.136]:51346 "EHLO out0-136.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229565AbiA0Gyw (ORCPT ); Thu, 27 Jan 2022 01:54:52 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R301e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018047213;MF=houwenlong.hwl@antgroup.com;NM=1;PH=DS;RN=5;SR=0;TI=SMTPD_---.MiyL62r_1643266489; Received: from localhost(mailfrom:houwenlong.hwl@antgroup.com fp:SMTPD_---.MiyL62r_1643266489) by smtp.aliyun-inc.com(127.0.0.1); Thu, 27 Jan 2022 14:54:50 +0800 From: "Hou Wenlong" To: kvm@vger.kernel.org Cc: Hou Wenlong , Sean Christopherson , Paolo Bonzini , linux-kernel@vger.kernel.org Subject: [PATCH v2] KVM: eventfd: Fix false positive RCU usage warning Date: Thu, 27 Jan 2022 14:54:49 +0800 Message-Id: X-Mailer: git-send-email 2.31.1 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: Hou Wenlong Fix the following false positive warning: ============================= WARNING: suspicious RCU usage 5.16.0-rc4+ #57 Not tainted ----------------------------- arch/x86/kvm/../../../virt/kvm/eventfd.c:484 RCU-list traversed in non-reader section!! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 3 locks held by fc_vcpu 0/330: #0: ffff8884835fc0b0 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x88/0x6f0 [kvm] #1: ffffc90004c0bb68 (&kvm->srcu){....}-{0:0}, at: vcpu_enter_guest+0x600/0x1860 [kvm] #2: ffffc90004c0c1d0 (&kvm->irq_srcu){....}-{0:0}, at: kvm_notify_acked_irq+0x36/0x180 [kvm] stack backtrace: CPU: 26 PID: 330 Comm: fc_vcpu 0 Not tainted 5.16.0-rc4+ Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 Call Trace: dump_stack_lvl+0x44/0x57 kvm_notify_acked_gsi+0x6b/0x70 [kvm] kvm_notify_acked_irq+0x8d/0x180 [kvm] kvm_ioapic_update_eoi+0x92/0x240 [kvm] kvm_apic_set_eoi_accelerated+0x2a/0xe0 [kvm] handle_apic_eoi_induced+0x3d/0x60 [kvm_intel] vmx_handle_exit+0x19c/0x6a0 [kvm_intel] vcpu_enter_guest+0x66e/0x1860 [kvm] kvm_arch_vcpu_ioctl_run+0x438/0x7f0 [kvm] kvm_vcpu_ioctl+0x38a/0x6f0 [kvm] __x64_sys_ioctl+0x89/0xc0 do_syscall_64+0x3a/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae Since kvm_unregister_irq_ack_notifier() does synchronize_srcu(&kvm->irq_srcu), i.e. kvm->irq_ack_notifier_list is protected by kvm->irq_srcu. And kvm->irq_srcu SRCU read lock is held in kvm_notify_acked_irq(), it's a false positive warning. Use hlist_for_each_entry_srcu() instead of hlist_for_each_entry_rcu() as it also checkes if the right lock is held. Reviewed-by: Sean Christopherson Signed-off-by: Hou Wenlong --- virt/kvm/eventfd.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) -- 2.31.1 diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c index 2ad013b8bde9..59b1dd4a549e 100644 --- a/virt/kvm/eventfd.c +++ b/virt/kvm/eventfd.c @@ -463,8 +463,8 @@ bool kvm_irq_has_notifier(struct kvm *kvm, unsigned irqchip, unsigned pin) idx = srcu_read_lock(&kvm->irq_srcu); gsi = kvm_irq_map_chip_pin(kvm, irqchip, pin); if (gsi != -1) - hlist_for_each_entry_rcu(kian, &kvm->irq_ack_notifier_list, - link) + hlist_for_each_entry_srcu(kian, &kvm->irq_ack_notifier_list, + link, srcu_read_lock_held(&kvm->irq_srcu)) if (kian->gsi == gsi) { srcu_read_unlock(&kvm->irq_srcu, idx); return true; @@ -480,8 +480,8 @@ void kvm_notify_acked_gsi(struct kvm *kvm, int gsi) { struct kvm_irq_ack_notifier *kian; - hlist_for_each_entry_rcu(kian, &kvm->irq_ack_notifier_list, - link) + hlist_for_each_entry_srcu(kian, &kvm->irq_ack_notifier_list, + link, srcu_read_lock_held(&kvm->irq_srcu)) if (kian->gsi == gsi) kian->irq_acked(kian); }