From patchwork Thu Jan 30 13:15:24 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Huth X-Patchwork-Id: 13954583 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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id AD5C5C02194 for ; Thu, 30 Jan 2025 13:17:41 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tdUPq-00084Y-8Q; Thu, 30 Jan 2025 08:17:06 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tdUOw-0007O7-Rp for qemu-devel@nongnu.org; Thu, 30 Jan 2025 08:16:12 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tdUOt-00006t-6Z for qemu-devel@nongnu.org; Thu, 30 Jan 2025 08:16:08 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1738242966; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=qV+61rvCL4A0t8T5oUkBk1b0e0MFCHm3CI8peZGVBkU=; b=eGiGVgNp2wJeVDaE04Vw1QQiDHlE9wwMInIPlnJqfcuhXD2kGaCbR5NAQ55HPZfNadBJDq gFU5FQGUzSjD53WM5lCJhSPzKwdCn5lirYMeY4TnSyyF3JyS4kX0FebzYmmXQKWslTMIS9 iSsbRAL8EP/dyw3AtKW5gQ6wcHarXgs= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-390-HPCoOzYHMJu39-l2FkUQMg-1; Thu, 30 Jan 2025 08:16:05 -0500 X-MC-Unique: HPCoOzYHMJu39-l2FkUQMg-1 X-Mimecast-MFC-AGG-ID: HPCoOzYHMJu39-l2FkUQMg Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 5CD8F1801F14; Thu, 30 Jan 2025 13:16:04 +0000 (UTC) Received: from thuth-p1g4.redhat.com (unknown [10.39.192.95]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id CEA4D30001BE; Thu, 30 Jan 2025 13:16:02 +0000 (UTC) From: Thomas Huth To: qemu-devel@nongnu.org Cc: Stefan Hajnoczi , Ilya Leoshkevich Subject: [PULL 10/20] hw/s390x/s390-virtio-ccw: Fix a record/replay deadlock Date: Thu, 30 Jan 2025 14:15:24 +0100 Message-ID: <20250130131535.91297-11-thuth@redhat.com> In-Reply-To: <20250130131535.91297-1-thuth@redhat.com> References: <20250130131535.91297-1-thuth@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.133.124; envelope-from=thuth@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -33 X-Spam_score: -3.4 X-Spam_bar: --- X-Spam_report: (-3.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.3, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org From: Ilya Leoshkevich Booting an s390x VM in record/replay mode hangs due to a deadlock between rr_cpu_thread_fn() and s390_machine_reset(). The former needs the record/replay mutex held by the latter, and the latter waits until the former completes its run_on_cpu() request. Fix by temporarily dropping the record/replay mutex, like it's done in pause_all_vcpus(). Signed-off-by: Ilya Leoshkevich Message-ID: <20250124112625.23050-1-iii@linux.ibm.com> Signed-off-by: Thomas Huth --- hw/s390x/s390-virtio-ccw.c | 24 +++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-) diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c index 3af613d4e9..b069303592 100644 --- a/hw/s390x/s390-virtio-ccw.c +++ b/hw/s390x/s390-virtio-ccw.c @@ -48,6 +48,7 @@ #include "kvm/kvm_s390x.h" #include "hw/virtio/virtio-md-pci.h" #include "hw/s390x/virtio-ccw-md.h" +#include "system/replay.h" #include CONFIG_DEVICES static Error *pv_mig_blocker; @@ -454,6 +455,18 @@ static void s390_machine_reset(MachineState *machine, ResetType type) CPUState *cs, *t; S390CPU *cpu; + /* + * Temporarily drop the record/replay mutex to let rr_cpu_thread_fn() + * process the run_on_cpu() requests below. This is safe, because at this + * point one of the following is true: + * - All CPU threads are not running, either because the machine is being + * initialized, or because the guest requested a reset using diag 308. + * There is no risk to desync the record/replay state. + * - A snapshot is about to be loaded. The record/replay state consistency + * is not important. + */ + replay_mutex_unlock(); + /* get the reset parameters, reset them once done */ s390_ipl_get_reset_request(&cs, &reset_type); @@ -533,7 +546,7 @@ static void s390_machine_reset(MachineState *machine, ResetType type) * went wrong. */ s390_cpu_set_state(S390_CPU_STATE_OPERATING, cpu); - return; + goto out_lock; } run_on_cpu(cs, s390_do_cpu_load_normal, RUN_ON_CPU_NULL); @@ -546,6 +559,15 @@ static void s390_machine_reset(MachineState *machine, ResetType type) run_on_cpu(t, s390_do_cpu_set_diag318, RUN_ON_CPU_HOST_ULONG(0)); } s390_ipl_clear_reset_request(); + +out_lock: + /* + * Re-take the record/replay mutex, temporarily dropping the BQL in order + * to satisfy the ordering requirements. + */ + bql_unlock(); + replay_mutex_lock(); + bql_lock(); } static void s390_machine_device_pre_plug(HotplugHandler *hotplug_dev,