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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 72E34C43217 for ; Wed, 9 Feb 2022 18:57:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241561AbiBIS5S (ORCPT ); Wed, 9 Feb 2022 13:57:18 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54818 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241043AbiBIS4y (ORCPT ); Wed, 9 Feb 2022 13:56:54 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 66876C05CB88; Wed, 9 Feb 2022 10:56:57 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 0481D617F4; Wed, 9 Feb 2022 18:56:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A2401C36AE9; Wed, 9 Feb 2022 18:56:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1644433016; bh=Y1O2CIN5EafAGmWxHeytfPsnxX2uH0gjcXAlhd6vK4E=; h=From:To:Cc:Subject:Date:From; b=uAbtZrTG2ed+w156dyvOR6Rw9pS3Kj9qdiJqZNXxmUT/0/LKIQi8mlBZXU8/e0pUN ZLK9ssiFEuwYbWBdNHpbcibZ0eDWT3ysZX9pm4KKzbkElHI4cMGSJJIAlJishkOLlt T+Zaa2GXJ5PJ6SQPp76rMX1vjoaLyVA2GHkaPoUAJY1nMxr8fp67zVezkOUUtVgvlg WRf1aT+blnlm5OEYsPdK0TGmefSq3JM+jJR5VmDJouUq77ha/zhkgdH4f0XPACj6Sj z0XRvz2jWsZFdpejmZoPh1Oh3ywRRVmiDD6N1so7HuEWad4gg6m1vLMwVA9vjkXogX DccN/1AWe5/PA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Hou Wenlong , Sean Christopherson , Paolo Bonzini , Sasha Levin , kvm@vger.kernel.org Subject: [PATCH MANUALSEL 5.15 1/8] KVM: eventfd: Fix false positive RCU usage warning Date: Wed, 9 Feb 2022 13:56:46 -0500 Message-Id: <20220209185653.48833-1-sashal@kernel.org> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: Hou Wenlong [ Upstream commit 6a0c61703e3a5d67845a4b275e1d9d7bc1b5aad7 ] 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), kvm->irq_ack_notifier_list is protected by kvm->irq_srcu. In fact, kvm->irq_srcu SRCU read lock is held in kvm_notify_acked_irq(), making it a false positive warning. So use hlist_for_each_entry_srcu() instead of hlist_for_each_entry_rcu(). Reviewed-by: Sean Christopherson Signed-off-by: Hou Wenlong Message-Id: Signed-off-by: Paolo Bonzini Signed-off-by: Sasha Levin --- virt/kvm/eventfd.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c index e996989cd580e..5b874e7ba36fd 100644 --- a/virt/kvm/eventfd.c +++ b/virt/kvm/eventfd.c @@ -456,8 +456,8 @@ 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; @@ -473,8 +473,8 @@ 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); } -- 2.34.1