From patchwork Wed Aug 28 10:09:12 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Prasad Pandit X-Patchwork-Id: 13781041 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 2972EC54E93 for ; Wed, 28 Aug 2024 10:10:21 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sjFcN-0004y6-VX; Wed, 28 Aug 2024 06:09:36 -0400 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 1sjFcM-0004sb-GY for qemu-devel@nongnu.org; Wed, 28 Aug 2024 06:09:34 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sjFcJ-0003Ud-6I for qemu-devel@nongnu.org; Wed, 28 Aug 2024 06:09:34 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1724839769; 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; bh=iVCiW6Inyr5fASxyaJc5B66b8YxNEOjxQl3QaxrMEWw=; b=gFLUj65DjCg3pbOsYixhHlliYeY6M0nXOoadosn/AMoaZg6PkDuTTcGWToQbjLlD80vfk6 orZZPLr05bSmtYUwzA/KqqErNhzNRmAaB2gNdtjQANlL1X6PXpa6t4t544cAbuk2A/jdC7 EAywjmHVutnWdXPnekYXJIRf31hyrfI= Received: from mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-77-LDK4lNOKPtiYdWRcVANqdg-1; Wed, 28 Aug 2024 06:09:26 -0400 X-MC-Unique: LDK4lNOKPtiYdWRcVANqdg-1 Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (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-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 6E21C1954B31; Wed, 28 Aug 2024 10:09:25 +0000 (UTC) Received: from kaapi.redhat.com (unknown [10.39.192.70]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 197DB1955F1B; Wed, 28 Aug 2024 10:09:20 +0000 (UTC) From: Prasad Pandit To: qemu-devel@nongnu.org Cc: mst@redhat.com, farosas@suse.de, jasowang@redhat.com, mcoqueli@redhat.com, peterx@redhat.com, Prasad Pandit Subject: [PATCH v2 0/2] Postcopy migration and vhost-user errors Date: Wed, 28 Aug 2024 15:39:12 +0530 Message-ID: <20240828100914.105728-1-ppandit@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 Received-SPF: pass client-ip=170.10.129.124; envelope-from=ppandit@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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: Prasad Pandit Hello, * virsh(1) offers multiple options to initiate Postcopy migration: 1) virsh migrate --postcopy --postcopy-after-precopy 2) virsh migrate --postcopy + virsh migrate-postcopy 3) virsh migrate --postcopy --timeout --timeout-postcopy When Postcopy migration is invoked via method (2) or (3) above, the migrated guest on the destination host hangs sometimes. * During Postcopy migration, multiple threads are spawned on the destination host to start the guest and setup devices. One such thread starts vhost device via vhost_dev_start() function and another called fault_thread handles page faults in user space using kernel's userfaultfd(2) system. * When fault_thread exits upon completion of Postcopy migration, it sends a 'postcopy_end' message to the vhost-user device. But sometimes 'postcopy_end' message is sent while vhost device is being setup via vhost_dev_start(). Thread-1 Thread-2 vhost_dev_start postcopy_ram_incoming_cleanup vhost_device_iotlb_miss postcopy_notify vhost_backend_update_device_iotlb vhost_user_postcopy_notifier vhost_user_send_device_iotlb_msg vhost_user_postcopy_end process_message_reply process_message_reply vhost_user_read vhost_user_read vhost_user_read_header vhost_user_read_header "Fail to update device iotlb" "Failed to receive reply to postcopy_end" This creates confusion when vhost device receives 'postcopy_end' message while it is still trying to update IOTLB entries. This seems to leave the guest in a stranded/hung state because fault_thread has exited saying Postcopy migration has ended, but vhost-device is probably still expecting updates. QEMU logs following errors on the destination host === ... qemu-kvm: vhost_user_read_header: 700871,700871: Failed to read msg header. Flags 0x0 instead of 0x5. qemu-kvm: vhost_device_iotlb_miss: 700871,700871: Fail to update device iotlb qemu-kvm: vhost_user_postcopy_end: 700871,700900: Failed to receive reply to postcopy_end qemu-kvm: vhost_user_read_header: 700871,700871: Failed to read msg header. Flags 0x0 instead of 0x5. qemu-kvm: vhost_device_iotlb_miss: 700871,700871: Fail to update device iotlb qemu-kvm: vhost_user_read_header: 700871,700871: Failed to read msg header. Flags 0x8 instead of 0x5. qemu-kvm: vhost_device_iotlb_miss: 700871,700871: Fail to update device iotlb qemu-kvm: vhost_user_read_header: 700871,700871: Failed to read msg header. Flags 0x16 instead of 0x5. qemu-kvm: vhost_device_iotlb_miss: 700871,700871: Fail to update device iotlb qemu-kvm: vhost_user_read_header: 700871,700871: Failed to read msg header. Flags 0x0 instead of 0x5. qemu-kvm: vhost_device_iotlb_miss: 700871,700871: Fail to update device iotlb === * Couple of patches here help to fix/handle these errors. Thank you. --- Prasad Pandit (2): vhost: fail device start if iotlb update fails vhost-user: add a request-reply lock hw/virtio/vhost-user.c | 74 ++++++++++++++++++++++++++++++++++ hw/virtio/vhost.c | 6 ++- include/hw/virtio/vhost-user.h | 3 ++ 3 files changed, 82 insertions(+), 1 deletion(-) -- 2.46.0