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 614D7D2E009 for ; Fri, 5 Dec 2025 06:47:15 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vRPam-0002ZG-Ff; Fri, 05 Dec 2025 01:47:00 -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 1vRPaj-0002Ys-KI for qemu-devel@nongnu.org; Fri, 05 Dec 2025 01:46:57 -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 1vRPah-0004VL-KN for qemu-devel@nongnu.org; Fri, 05 Dec 2025 01:46:57 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1764917213; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=+9TIULzHZ+/aPStUjHpAud9RvJt46Xfv6HIwan4IJmU=; b=UmYxmtAF8UcTHc/eKECdwaqlfBSb0kMk7jHDmCXdiu4C7rFM3z/HWrLvXwaWUrR105i24c YJhztqo9l6MSNnaKV+36ZZT/LjtcWZCFKqaYBkP+182OpbkQYRmUR0JBLvRUfkeS2aB+Ob mxAFAAs4EZVDelKJpHPK2hhAEo3QjTU= Received: from mx-prod-mc-08.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-686-FIgp6_MpMMeVsInsRsWxdw-1; Fri, 05 Dec 2025 01:46:50 -0500 X-MC-Unique: FIgp6_MpMMeVsInsRsWxdw-1 X-Mimecast-MFC-AGG-ID: FIgp6_MpMMeVsInsRsWxdw_1764917208 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 08AE518002ED; Fri, 5 Dec 2025 06:46:48 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.45.242.7]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id EDB741800577; Fri, 5 Dec 2025 06:46:46 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 44AAE21E6A27; Fri, 05 Dec 2025 07:46:44 +0100 (CET) From: Markus Armbruster To: Jason Wang Cc: Ben Chaney , qemu-devel@nongnu.org, Peter Xu , Fabiano Rosas , "Michael S. Tsirkin" , Stefano Garzarella , Alex Williamson , =?utf-8?Q?C=C3=A9dric?= Le Goater , Eric Blake , Stefan Weil , Daniel P. =?utf-8?Q?Berrang=C3=A9?= , Paolo Bonzini , Hamza Khan , Mark Kanda , Joshua Hunt , Max Tottenham , Steve Sistare Subject: Re: [PATCH v3 6/8] tap: cpr support In-Reply-To: (Jason Wang's message of "Fri, 5 Dec 2025 08:51:43 +0800") References: <20251203-cpr-tap-v3-0-3c12e0a61f8e@akamai.com> <20251203-cpr-tap-v3-6-3c12e0a61f8e@akamai.com> <874iq6mzx5.fsf@pond.sub.org> Date: Fri, 05 Dec 2025 07:46:44 +0100 Message-ID: <877bv11l4b.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Received-SPF: pass client-ip=170.10.133.124; envelope-from=armbru@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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-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 Jason Wang writes: > Hi Markus, > > On Thu, Dec 4, 2025 at 4:09=E2=80=AFPM Markus Armbruster wrote: >> >> Ben Chaney writes: >> >> > From: Steve Sistare >> > >> > Provide the cpr=3Don option to preserve TAP and vhost descriptors duri= ng >> > cpr-transfer, so the management layer does not need to create a new >> > device for the target. >> > >> > Save all tap fd's in canonical order, leveraging the index argument of >> > cpr_save_fd. For the i'th queue, the tap device fd is saved at index = 2*i, >> > and the vhostfd (if any) at index 2*i+1. >> > >> > tap and vhost fd's are passed by name to the monitor when a NIC is hot >> > plugged, but the name is not known to qemu after cpr. Allow the manag= er >> > to pass -1 for the fd "name" in the new qemu args to indicate that QEMU >> > should search for a saved value. Example: >> > >> > -netdev tap,id=3Dhostnet2,fds=3D-1:-1,vhostfds=3D-1:-1,cpr=3Don >> >> Hmm. See below. >> >> > >> > Signed-off-by: Steve Sistare >> > Signed-off-by: Ben Chaney >> >> [...] >> >> > diff --git a/qapi/net.json b/qapi/net.json >> > index 118bd34965..264213b5d9 100644 >> > --- a/qapi/net.json >> > +++ b/qapi/net.json >> > @@ -355,6 +355,8 @@ >> ## >> # @NetdevTapOptions: >> # >> # Used to configure a host TAP network interface backend. >> # >> # @ifname: interface name >> # >> # @fd: file descriptor of an already opened tap >> # >> # @fds: multiple file descriptors of already opened multiqueue capable >> # tap >> >> Not this patch's fault: the interface is misguided, and its >> documentation inadequate. >> >> @fds is a string of file descriptor names or numbers separated by ':'. >> Not documented. I found out by reading the code. >> >> This violates QAPI design principle "no string parsing". It should be >> an array of strings. >> > > I agree with your concern. Just a note that this "fds" was introduced > before QAPI if I am not wrong. It's from 2013 (commit 264986e2c8f). QAPI was still young then (netdev_add had been QAPIfied less than a year ago), we had much to learn, and interface review barely happened. All understandable, and no reason to throw shade on anyone involved :)