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 3949610A88D4 for ; Thu, 26 Mar 2026 15:55:50 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1w5n3R-0001ae-NB; Thu, 26 Mar 2026 11:55:29 -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 1w5n3Q-0001aL-8Q for qemu-devel@nongnu.org; Thu, 26 Mar 2026 11:55:28 -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 1w5n3O-0008MT-Ph for qemu-devel@nongnu.org; Thu, 26 Mar 2026 11:55:27 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1774540525; 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=HkhsZ+4WYb4UpPprivDQbnPhli6Yt/ZiU2dF3YO8xwM=; b=DWdkQCXGLIxFr6hv9Qy5lqYjFs0cBhMDtEVC0Ws4PbBOWgkI1srdgFHxna72sSY5EvL4zA 5AAft5VirPPGgYT9JfelvVq901EmTU+ZyIBH7HhRQWS/gHlD2ayAgmQkXYLY0d95ySPJQq OBjlUkelto9awXvub1tyKkcOYF/GvQI= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-674-9AB8HI5TOiiMAQVC29dtyA-1; Thu, 26 Mar 2026 11:55:22 -0400 X-MC-Unique: 9AB8HI5TOiiMAQVC29dtyA-1 X-Mimecast-MFC-AGG-ID: 9AB8HI5TOiiMAQVC29dtyA_1774540520 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 7A9501800610; Thu, 26 Mar 2026 15:55:19 +0000 (UTC) Received: from localhost (unknown [10.45.226.37]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 8779D19560B1; Thu, 26 Mar 2026 15:55:16 +0000 (UTC) Date: Thu, 26 Mar 2026 11:55:14 -0400 From: Stefan Hajnoczi To: Alexandr Moshkov Cc: qemu-devel@nongnu.org, virtio-fs@lists.linux.dev, zhenwei pi , Hanna Reitz , "yc-core@yandex-team.ru" , "Gonglei (Arei)" , Raphael Norwitz , Milan Zamazal , Jason Wang , Alex =?iso-8859-1?Q?Benn=E9e?= , qemu-block@nongnu.org, Pierrick Bouvier , Paolo Bonzini , "Michael S. Tsirkin" , Stefano Garzarella , Fam Zheng , Kevin Wolf Subject: Re: [PATCH v2 0/4] vhost-user-blk: fix compatibility with older qemu versions Message-ID: <20260326155514.GF758087@fedora> References: <20260311084728.751169-1-dtalexundeer@yandex-team.ru> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="mhkaxRLYx8MX0uJr" Content-Disposition: inline In-Reply-To: <20260311084728.751169-1-dtalexundeer@yandex-team.ru> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 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, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=unavailable 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 --mhkaxRLYx8MX0uJr Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Mar 11, 2026 at 01:47:24PM +0500, Alexandr Moshkov wrote: > v1 -> v2: > - reorganize commits: make refactor commits first, then core semantic cha= nge > - add additional pre_save check for inflight migration possibility >=20 > --- >=20 > This is a small continuation of my series about inflight migration for vh= ost-user-blk. >=20 > This series is designed to solve the problem of compatibility with older = versions of qemu, where this feature has not yet been introduced (for examp= le, if we want to downgrade versions due to some problems). >=20 > In the current version for vhost-user-blk, this feature is enabled using = the parameter and further migration of the inflight region will depend on w= hether the vhost-user has accepted the new protocol feature or not. This cr= eates an inconvenient dependency, because there is no way to disable this f= eature without reconnecting to the backend. > This series slightly changes the semantics of the introduced protocol fea= ture VHOST_USER_PROTOCOL_F_GET_VRING_BASE_INFLIGHT. Enabling this feature a= dds a new parameter for GET_VRING_BASE message - skip_drain, which allows t= o control drain in-flight requests on the backend. >=20 > Thus, user can enable or disable inflight-migration param for vhost-user-= blk to maintain compatibility with older versions of QEMU. Can you describe what the user needs to do in more detail? While the patch series introduces a way to tell the vhost-user back-end whether or not to use inflight migration at runtime, I don't see a way for the user to enable/disable inflight migration at runtime in QEMU. So how does the user migrate back to an old QEMU if the current VM was launched with inflight-migration=3Don? Stefan --mhkaxRLYx8MX0uJr Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQEzBAEBCgAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmnFVuIACgkQnKSrs4Gr c8g/nAf/fg5Y8ZNvlhaxNPN1jfI8plT7beo1az0FD+g2faVR4zLuDlumqocFziQQ H7qgyugiiJrgdT41sk3AXd/SKiqGgTUAnVLzpYaYFdfRJLIeomJLHPZQxXIO/+Ye CfCZL0e7Diwt/442ISK3jRwlBcCamEl5frLvn4PGSYPCLzcxds7gsAPN6dEmnGhm VgZWc7qs6GXTWD3O/WOZkdk3QOR64cRIIE4GVt6w4zszzliRlvqIv7i4VXobCp5Z 83dnaz6xsrR8wT4j3f6TrlJBLZipe+BBYRHlM/mDl+K5nQ5TKrTuTUxrD8ZieobT ApWq9QsUqScul4vR+NlhwQHXaYhXgQ== =7g79 -----END PGP SIGNATURE----- --mhkaxRLYx8MX0uJr--