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 F1467C27C76 for ; Wed, 25 Jan 2023 19:46:58 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pKlip-0005cl-7U; Wed, 25 Jan 2023 14:46:15 -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 1pKlin-0005cc-4f for qemu-devel@nongnu.org; Wed, 25 Jan 2023 14:46:13 -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 1pKlii-0002NU-6S for qemu-devel@nongnu.org; Wed, 25 Jan 2023 14:46:12 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1674675965; 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=uNr88SPLYYvo3iE3N0wzTOEQEswp1GT/mJbLFPKrOTo=; b=CDTX7xeYNi2cmB4DL4kU4wKb/rrWNuao2aW0BL7fzooLF7nKwcOWeT37SlJrfe+1/ijEe8 uYr0cqPQ+OdRjuhKxpbxX3pVxL3YTNsZ0ZaXwTmSlwIj396B40cXohTOYzs9FJvSIOOfwd vhosRThtF6NgxfENcDiX1RQVGqaywfc= Received: from mimecast-mx02.redhat.com (mx3-rdu2.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-492-mUJoueHcNE-BVFENXRQgpQ-1; Wed, 25 Jan 2023 14:46:03 -0500 X-MC-Unique: mUJoueHcNE-BVFENXRQgpQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 453333804073; Wed, 25 Jan 2023 19:46:03 +0000 (UTC) Received: from localhost (unknown [10.39.192.105]) by smtp.corp.redhat.com (Postfix) with ESMTP id 971F12166B26; Wed, 25 Jan 2023 19:46:02 +0000 (UTC) Date: Wed, 25 Jan 2023 14:46:00 -0500 From: Stefan Hajnoczi To: Anton Kuchin Cc: qemu-devel@nongnu.org, virtio-fs@redhat.com, Markus Armbruster , Eric Blake , "Dr. David Alan Gilbert" , Juan Quintela , yc-core@yandex-team.ru, "Michael S. Tsirkin" Subject: Re: [PATCH] vhost-user-fs: add capability to allow migration Message-ID: References: <20230115170903.3416105-1-antonkuchin@yandex-team.ru> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="ygiLBLz14JAm0xgO" Content-Disposition: inline In-Reply-To: <20230115170903.3416105-1-antonkuchin@yandex-team.ru> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 Received-SPF: pass client-ip=170.10.133.124; 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_H2=-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 --ygiLBLz14JAm0xgO Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sun, Jan 15, 2023 at 07:09:03PM +0200, Anton Kuchin wrote: > Now any vhost-user-fs device makes VM unmigratable, that also prevents > qemu update without stopping the VM. In most cases that makes sense > because qemu has no way to transfer FUSE session state. >=20 > But we can give an option to orchestrator to override this if it can > guarantee that state will be preserved (e.g. it uses migration to > update qemu and dst will run on the same host as src and use the same > socket endpoints). >=20 > This patch keeps default behavior that prevents migration with such devic= es > but adds migration capability 'vhost-user-fs' to explicitly allow migrati= on. >=20 > Signed-off-by: Anton Kuchin > --- > hw/virtio/vhost-user-fs.c | 25 ++++++++++++++++++++++++- > qapi/migration.json | 7 ++++++- > 2 files changed, 30 insertions(+), 2 deletions(-) Hi Anton, Sorry for holding up your work with the discussions that we had. I still feel it's important to agree on command-line and/or vhost-user protocol changes that will be able to support non-migratable, stateless migration/reconnect, and stateful migration vhost-user-fs back-ends. All three will exist. As a next step, could you share your code that implements the QEMU side of stateless migration? I think that will make it clearer whether a command-line option (migration capability or per-device) is sufficient or whether the vhost-user protocol needs to be extended. If the vhost-user protocol is extended then maybe no user-visible changes are necessary. QEMU will know if the vhost-user-fs backend supports migration and which type of migration. It can block migration in cases where it's not possible. Thanks, Stefan --ygiLBLz14JAm0xgO Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmPRhvgACgkQnKSrs4Gr c8izOgf/byjN54t5uv1VugMSLblTq6dHpjGJDpdmjIb7QjBk/VTe57XFhBOp4VEg mlDNTVHBc4lU0NHize5dueoW8wUMKT+gQq8Tb6O5VabHZA1NJVQ2TOrlwWt4Q6bn eS3IAIRB+4JoFPlYzJMa9MhkEjbnlJ6yYpVvuo8tNfTOMCHdirDiBWx/P43F0X2W 6TNkpr56+NixIO5E0wfnKPfkiS083h9PqVYFy7WH6debjBM+IRyBSaRSaLpgJRHt a8D4rjb+XFxW71qFFMK3XWa/8sy2MfLCW2oPC1Zc137ItjqxaxRwqiZKsrU79GLi WuQcgk2e7RYTUbLRfJXdbrH27j0N8g== =VwlJ -----END PGP SIGNATURE----- --ygiLBLz14JAm0xgO--