From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Mon, 25 Sep 2023 15:04:31 -0400 From: Stefan Hajnoczi Message-ID: <20230925190431.GB323580@fedora> References: <20230915102531.55894-1-hreitz@redhat.com> <20230915102531.55894-2-hreitz@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="G/2yNfBg+jWKHP+w" Content-Disposition: inline In-Reply-To: <20230915102531.55894-2-hreitz@redhat.com> Subject: Re: [Virtio-fs] [PATCH v3 1/5] vhost-user.rst: Migrating back-end-internal state List-Id: Development discussions about virtio-fs List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Hanna Czenczek Cc: qemu-devel@nongnu.org, virtio-fs@redhat.com, "Michael S . Tsirkin" , Eugenio =?iso-8859-1?Q?P=E9rez?= , German Maglione --G/2yNfBg+jWKHP+w Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Sep 15, 2023 at 12:25:26PM +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 | 170 ++++++++++++++++++++++++++++++++++++ > 1 file changed, 170 insertions(+) Great documentation! Reviewed-by: Stefan Hajnoczi --G/2yNfBg+jWKHP+w Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmUR2b8ACgkQnKSrs4Gr c8iMLwf/f5GkieEgVbXuahClGPFQAjBdciOmypJvZyRxcTvOhb4fu6UOJRRSe7Sr +r8lF6GyaMpq3MyT58JgMVL9tKRaNNGNEEzVPVqrB2sugMet2ZHZA7pSaGKa8Y8R q9dEeSTmBBZyX0DXlFcP64PCjU6GmooJ0evS0kIMdIFgv4wUW12MiDtP3YDgwphD iALLapDCmcvMOUESc6KSpIeDjwU4qrUmpGzhqdQzoh4FJaKjuLaWZuye+Nlnvens SXpvgTlMJNzBZrNuqtGJY7bnUPYbQfXvcTVQxMF241mq11IuiUndEi3D5SVLOvlK +P3n0iB1UF6Jcz+R8mwswUxS91xs6g== =2EeV -----END PGP SIGNATURE----- --G/2yNfBg+jWKHP+w-- 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 2A6FFCD54BE for ; Mon, 25 Sep 2023 19:04:52 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qkqsr-0007Ki-Qc; Mon, 25 Sep 2023 15:04:41 -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 1qkqsp-00073Q-ID for qemu-devel@nongnu.org; Mon, 25 Sep 2023 15:04:39 -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 1qkqsl-0006Fc-Sr for qemu-devel@nongnu.org; Mon, 25 Sep 2023 15:04:39 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1695668674; 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=TpY7LsIzo2Zh2ob1psGzR4n7GX8ELbBC4TE+wnWRrtQ=; b=B2HjhPXq1DO33uRLl0Wa5y9KuQuX5aUeUGTzXVC/2CK0VVyMGdmN7VbXmL+Dfdo3iGv6qP 3fMK6dmbGEXQUCjArESYvZehaojsHXECb7tpFBeZlFp4NXy1rlLgQab3F3zPS+SOirMCzd XABy/KnNBv7KkjmvTG7U4uDosGoMKnI= 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-137--ZEHfLZjPemuPD6F1fRb6Q-1; Mon, 25 Sep 2023 15:04:33 -0400 X-MC-Unique: -ZEHfLZjPemuPD6F1fRb6Q-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 DFEA829AB411 for ; Mon, 25 Sep 2023 19:04:32 +0000 (UTC) Received: from localhost (unknown [10.39.194.68]) by smtp.corp.redhat.com (Postfix) with ESMTP id 61B4F711293; Mon, 25 Sep 2023 19:04:32 +0000 (UTC) Date: Mon, 25 Sep 2023 15:04:31 -0400 From: Stefan Hajnoczi To: Hanna Czenczek Cc: qemu-devel@nongnu.org, virtio-fs@redhat.com, "Michael S . Tsirkin" , Eugenio =?iso-8859-1?Q?P=E9rez?= , German Maglione Subject: Re: [PATCH v3 1/5] vhost-user.rst: Migrating back-end-internal state Message-ID: <20230925190431.GB323580@fedora> References: <20230915102531.55894-1-hreitz@redhat.com> <20230915102531.55894-2-hreitz@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="G/2yNfBg+jWKHP+w" Content-Disposition: inline In-Reply-To: <20230915102531.55894-2-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: 12 X-Spam_score: 1.2 X-Spam_bar: + X-Spam_report: (1.2 / 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, RCVD_IN_SBL_CSS=3.335, SPF_HELO_NONE=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: 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 --G/2yNfBg+jWKHP+w Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Sep 15, 2023 at 12:25:26PM +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 | 170 ++++++++++++++++++++++++++++++++++++ > 1 file changed, 170 insertions(+) Great documentation! 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