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 X-Spam-Level: X-Spam-Status: No, score=-7.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D4BE3C433C1 for ; Mon, 22 Mar 2021 05:59:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A201F61925 for ; Mon, 22 Mar 2021 05:59:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229760AbhCVF6m (ORCPT ); Mon, 22 Mar 2021 01:58:42 -0400 Received: from mx2.suse.de ([195.135.220.15]:52116 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229613AbhCVF6g (ORCPT ); Mon, 22 Mar 2021 01:58:36 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1616392715; h=from:from:reply-to: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=rpfcsvKFLtYwXTwkcaD3SMIT07anvDjM2o1RlVIT5tQ=; b=a83pjg1mYWQrab/nZveqt0sAahlov+NEHXk/jorvLIE3o8R4oh0oZqPIA8d80cKrO37GZ3 82nr32pVBkDB3/3ybYnkLsI2JAB5W627O1uuv2/nPXI2yl29eExydW3feZpmMZx/cz6krA yAeIO+L3z6+ftuUNVs4wX2726g9GmEk= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 302E5AC1F; Mon, 22 Mar 2021 05:58:35 +0000 (UTC) Subject: Re: [net-next 1/2] xen-netback: add module parameter to disable ctrl-ring To: Leon Romanovsky , "Hsu, Chiahao" Cc: Andrew Lunn , netdev@vger.kernel.org, wei.liu@kernel.org, paul@xen.org, davem@davemloft.net, kuba@kernel.org, xen-devel@lists.xenproject.org References: <20210311225944.24198-1-andyhsu@amazon.com> <64f5c7a8-cc09-3a7f-b33b-a64d373aed60@amazon.com> <12f643b5-7a35-d960-9b1f-22853aea4b4c@amazon.com> From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= Message-ID: Date: Mon, 22 Mar 2021 06:58:34 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="GEck0MXAkH1N6s1uP2AhJml1gohEKJuvu" Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --GEck0MXAkH1N6s1uP2AhJml1gohEKJuvu Content-Type: multipart/mixed; boundary="XUP3wTaC5PcuOZo2Tj6lUqDgZCIZPhCqg"; protected-headers="v1" From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= To: Leon Romanovsky , "Hsu, Chiahao" Cc: Andrew Lunn , netdev@vger.kernel.org, wei.liu@kernel.org, paul@xen.org, davem@davemloft.net, kuba@kernel.org, xen-devel@lists.xenproject.org Message-ID: Subject: Re: [net-next 1/2] xen-netback: add module parameter to disable ctrl-ring References: <20210311225944.24198-1-andyhsu@amazon.com> <64f5c7a8-cc09-3a7f-b33b-a64d373aed60@amazon.com> <12f643b5-7a35-d960-9b1f-22853aea4b4c@amazon.com> In-Reply-To: --XUP3wTaC5PcuOZo2Tj6lUqDgZCIZPhCqg Content-Type: multipart/mixed; boundary="------------E31744AF77CBCB1800D0DE83" Content-Language: en-US This is a multi-part message in MIME format. --------------E31744AF77CBCB1800D0DE83 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 22.03.21 06:39, Leon Romanovsky wrote: > On Sun, Mar 21, 2021 at 06:54:52PM +0100, Hsu, Chiahao wrote: >> >=20 > <...> >=20 >>>> Typically there should be one VM running netback on each host, >>>> and having control over what interfaces or features it exposes is al= so >>>> important for stability. >>>> How about we create a 'feature flags' modparam, each bits is specifi= ed for >>>> different new features? >>> At the end, it will be more granular module parameter that user still= >>> will need to guess. >> I believe users always need to know any parameter or any tool's flag b= efore >> they use it. >> For example, before user try to set/clear this ctrl_ring_enabled, they= >> should already have basic knowledge about this feature, >> or else they shouldn't use it (the default value is same as before), a= nd >> that's also why we use the 'ctrl_ring_enabled' as parameter name. >=20 > It solves only forward migration flow. Move from machine A with no > option X to machine B with option X. It doesn't work for backward > flow. Move from machine B to A back will probably break. >=20 > In your flow, you want that users will set all module parameters for > every upgrade and keep those parameters differently per-version. I think the flag should be a per guest config item. Adding this item to the backend Xenstore nodes for netback to consume it should be rather easy. Yes, this would need a change in Xen tools, too, but it is the most flexible way to handle it. And in case of migration the information would be just migrated to the new host with the guest's config data. 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