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 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 617A1E9271B for ; Thu, 5 Oct 2023 17:46:55 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qoSQi-0006Ym-21; Thu, 05 Oct 2023 13:46:32 -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 1qoSQd-0006YA-36 for qemu-devel@nongnu.org; Thu, 05 Oct 2023 13:46:27 -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 1qoSQb-0005aS-MG for qemu-devel@nongnu.org; Thu, 05 Oct 2023 13:46:26 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1696527985; 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=RjCL+hkdyjqzcINXooArm8wGFV87J3hI+46yN8d26lU=; b=JyrlgoMaJ5cYgpioFX97U9yPPZS+hifyFcthgidM+ATDHoGwpC7IRnnDeD85LkCoQjNa8I mHiVbk55erFdLm76i4fQOvVqgDBtmox1VVcqi5bBDOxFfDH7rrwWGfylvGpf7T/PBolmNe k+/xFUUADqqRIhS5TnxQpFbfg39nx54= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-183-Rs0LfZuWPwyMtqmwkGfAxw-1; Thu, 05 Oct 2023 13:46:10 -0400 X-MC-Unique: Rs0LfZuWPwyMtqmwkGfAxw-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id EAE202812948; Thu, 5 Oct 2023 17:46:09 +0000 (UTC) Received: from localhost (unknown [10.39.192.20]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6AA3C47AD4A; Thu, 5 Oct 2023 17:46:09 +0000 (UTC) Date: Thu, 5 Oct 2023 13:46:08 -0400 From: Stefan Hajnoczi To: Hanna Czenczek Cc: qemu-devel@nongnu.org, virtio-fs@redhat.com, "Michael S . Tsirkin" , German Maglione , Eugenio =?iso-8859-1?Q?P=E9rez?= , Anton Kuchin Subject: Re: [PATCH v4 5/8] vhost-user.rst: Migrating back-end-internal state Message-ID: <20231005174608.GF1342722@fedora> References: <20231004125904.110781-1-hreitz@redhat.com> <20231004125904.110781-6-hreitz@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="jDuzzalqjlJwX7Gx" Content-Disposition: inline In-Reply-To: <20231004125904.110781-6-hreitz@redhat.com> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 Received-SPF: pass client-ip=170.10.129.124; envelope-from=stefanha@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_H4=0.001, RCVD_IN_MSPIKE_WL=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 --jDuzzalqjlJwX7Gx Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Oct 04, 2023 at 02:59:01PM +0200, Hanna Czenczek wrote: > For vhost-user devices, qemu can migrate the virtio state, but not the > back-end's internal state. To do so, we need to be able to transfer > this internal state between front-end (qemu) and back-end. >=20 > At this point, this new feature is added for the purpose of virtio-fs > migration. Because virtiofsd's internal state will not be too large, we > believe it is best to transfer it as a single binary blob after the > streaming phase. >=20 > These are the additions to the protocol: > - New vhost-user protocol feature VHOST_USER_PROTOCOL_F_DEVICE_STATE > - SET_DEVICE_STATE_FD function: Front-end and back-end negotiate a file > descriptor over which to transfer the state. > - CHECK_DEVICE_STATE: After the state has been transferred through the > file descriptor, the front-end invokes this function to verify > success. There is no in-band way (through the file descriptor) to > indicate failure, so we need to check explicitly. >=20 > Once the transfer FD has been established via SET_DEVICE_STATE_FD > (which includes establishing the direction of transfer and migration > phase), the sending side writes its data into it, and the reading side > reads it until it sees an EOF. Then, the front-end will check for > success via CHECK_DEVICE_STATE, which on the destination side includes > checking for integrity (i.e. errors during deserialization). >=20 > Signed-off-by: Hanna Czenczek > --- > docs/interop/vhost-user.rst | 172 ++++++++++++++++++++++++++++++++++++ > 1 file changed, 172 insertions(+) Reviewed-by: Stefan Hajnoczi --jDuzzalqjlJwX7Gx Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmUe9mAACgkQnKSrs4Gr c8j0pggAg8UjrOpW1KQrqs75pbu8eO2gSx9HQGModw59J4CVl1GHySIhKzi7VFQO Cyvq1wm3vbBJbDwvdeT1al791zvbu1yZgz6nFJZfzJnQ3p9OVYZY9gVSNN4S1gNK 0C71HUGh7Z+9Kf/IeGipgZHkr8VEgFNLZ1VdtvzLzadROBn4fQ71Pp5V54bnkSej WYOr05CvcUhZKXiudbRVHgddIK+/E1ghxAy1ITi9d2jGOFpHnKX7uKtalAiTLW81 lPTPl+YNJh5ks9IJ06u1NKnOXJMD37SqN6jv47WYtwRQRSsjZQ+ryxWQB2lCjnoc TAYgRoiG+6pBUPTkGkGKpEDpqM2l8A== =B0Ah -----END PGP SIGNATURE----- --jDuzzalqjlJwX7Gx--