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 lists1p.gnu.org (lists1p.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 83ED8CC6B1A for ; Tue, 13 Oct 2026 20:04:59 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1xGijf-0007DE-0y; Tue, 13 Oct 2026 16:04:31 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xGijd-0007CV-Hv for qemu-devel@nongnu.org; Tue, 13 Oct 2026 16:04:29 -0400 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 1xGijc-000373-0U for qemu-devel@nongnu.org; Tue, 13 Oct 2026 16:04:29 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1791921865; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=G6fRvMSISGYN0cvq3i5JYF1oBKCZb5mvRYaRSDHtYH0=; b=DvbDVSSwVfowRbHr9kDCCQQTLCuADUxdE4ge+0pykTykhqOB/gIjRkV1zwIZoOgNGwnu1c pqvx3aNAX4dHf3HgIwE7nDANkVKZj2P9c52/ga0IciB6TrB8ZJGu/x1C4qMUnj38fRiBzu gj0/ljpLztXtZT67fDaGW0KEuLZ0tWY= Received: from mx-prod-mc-05.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-588-1BDjJrh_Mj-BmOa0Zi_AIQ-1; Tue, 13 Oct 2026 20:04:22 +0000 X-MC-Unique: 1BDjJrh_Mj-BmOa0Zi_AIQ-1 X-Mimecast-MFC-AGG-ID: 1BDjJrh_Mj-BmOa0Zi_AIQ_1791921861 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (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-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 46B9C1953957; Tue, 13 Oct 2026 20:04:20 +0000 (UTC) Received: from redhat.com (headnet04.pony-001.prod.iad2.dc.redhat.com [10.2.32.116]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 7AF69180029C; Tue, 13 Oct 2026 20:04:17 +0000 (UTC) Date: Tue, 13 Oct 2026 15:04:14 -0500 From: Eric Blake To: Stefan Hajnoczi Cc: qemu-devel@nongnu.org, Pierrick Bouvier , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , akalenyu@redhat.com, Kevin Wolf , Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= , Fam Zheng , Paolo Bonzini , qemu-block@nongnu.org, Hanna Reitz , Benjamin Marzinski Subject: Re: [PATCH v2 7/8] scsi: clean up persistent reservation state after migration Message-ID: References: <20261013181752.1299456-1-stefanha@redhat.com> <20261013181752.1299456-8-stefanha@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261013181752.1299456-8-stefanha@redhat.com> User-Agent: NeoMutt/20260616 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass client-ip=170.10.133.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 10 X-Spam_score: 1.0 X-Spam_bar: + X-Spam_report: (1.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.24, 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_SBL_CSS=3.335, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development 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 On Tue, Oct 13, 2026 at 02:17:51PM -0400, Stefan Hajnoczi wrote: > Live migration of persistent reservations is designed to work without > coordination between the source and destination. The destination uses > the PREEMPT command to atomically take over the reservation or > unregister keys belonging to the source. This approach avoids race > conditions where other nodes in the cluster might acquire the > reservation and it minimizes communication during the downtime window. > > While this works at the SCSI level, this approach is incomplete when > using multipathd. Multipathd tracks registered keys and automatically > registers them again when paths come up. It is unaware that the > destination has preempted the reservation and therefore it will still > attempt to register the key on the source host. > > Use the new PR_HELPER_CLEANUP command to communicate with multipathd on > the source after migration completes successfully. The effect is similar > to REGISTER AND IGNORE EXISTING KEY, except it also discards > multipathd's state so that the source will no longer attempt to register > the key. > > PR_HELPER_CLEANUP is a QEMU-internal command that is rejected by > scsi_req_new(), so note that this command is not exposed to guests > although direct blk_aio_ioctl(SG_IO) calls can make use of it. > > Buglink: https://redhat.atlassian.net/browse/RHEL-274966 > Signed-off-by: Stefan Hajnoczi > --- > include/hw/scsi/scsi.h | 1 + > hw/scsi/scsi-disk.c | 21 ++++++++++++++++++++- > hw/scsi/scsi-generic.c | 29 +++++++++++++++++++++++++++++ > 3 files changed, 50 insertions(+), 1 deletion(-) > Reviewed-by: Eric Blake -- Eric Blake, Principal Software Engineer Red Hat, Inc. Virtualization: qemu.org | libguestfs.org