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 9976FC433C1 for ; Mon, 29 Mar 2021 05:05:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 73D1660190 for ; Mon, 29 Mar 2021 05:05:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230394AbhC2FER (ORCPT ); Mon, 29 Mar 2021 01:04:17 -0400 Received: from mx2.suse.de ([195.135.220.15]:54046 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229483AbhC2FEA (ORCPT ); Mon, 29 Mar 2021 01:04:00 -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=1616994239; 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=OltM0c4NXhUr2NOE/Q3F89i4bVBoS57i1Rx2yFWgD3E=; b=l3ScvgM94a17eS01J97dDdNVpwJv+oLPilJxq4/4kHTe5Vj2LFASIyuatiCGT81Hx1CZKe p9AMuEOoCKCQymfUXO9GFOcewOfdpgGdB21Au0Qz4RVzoVIdNDX4aY78bIcBqzl3HBwHUQ jbdXiojjjyg6YjABSuKn1e9f9U39qyk= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id DEB60B217; Mon, 29 Mar 2021 05:03:58 +0000 (UTC) Subject: Re: [net-next 1/2] xen-netback: add module parameter to disable ctrl-ring To: "Hsu, Chiahao" , Leon Romanovsky 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: <64f5c7a8-cc09-3a7f-b33b-a64d373aed60@amazon.com> <12f643b5-7a35-d960-9b1f-22853aea4b4c@amazon.com> From: Juergen Gross Message-ID: <3136e73f-d661-6f16-a3ce-1ee814dbedff@suse.com> Date: Mon, 29 Mar 2021 07:03:57 +0200 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="d2cqQLGfyAhEyqvbowhYCZOslEBwEsrxb" Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --d2cqQLGfyAhEyqvbowhYCZOslEBwEsrxb Content-Type: multipart/mixed; boundary="zX1ZuB5ENFZ9KeOGwPeJS5oD3rTOd9Oi5"; protected-headers="v1" From: Juergen Gross To: "Hsu, Chiahao" , Leon Romanovsky 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: <3136e73f-d661-6f16-a3ce-1ee814dbedff@suse.com> Subject: Re: [net-next 1/2] xen-netback: add module parameter to disable ctrl-ring References: <64f5c7a8-cc09-3a7f-b33b-a64d373aed60@amazon.com> <12f643b5-7a35-d960-9b1f-22853aea4b4c@amazon.com> In-Reply-To: --zX1ZuB5ENFZ9KeOGwPeJS5oD3rTOd9Oi5 Content-Type: multipart/mixed; boundary="------------5ACF9DB2D547D252A89E4091" Content-Language: en-US This is a multi-part message in MIME format. --------------5ACF9DB2D547D252A89E4091 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 28.03.21 22:46, Hsu, Chiahao wrote: >=20 >=20 > Leon Romanovsky =E6=96=BC 2021/3/22 08:13 =E5=AF=AB=E9=81=93: >> CAUTION: This email originated from outside of the organization. Do=20 >> not click links or open attachments unless you can confirm the sender = >> and know the content is safe. >> >> >> >> On Mon, Mar 22, 2021 at 08:01:17AM +0100, J=C3=BCrgen Gro=C3=9F wrote:= >>> On 22.03.21 07:48, Leon Romanovsky wrote: >>>> On Mon, Mar 22, 2021 at 06:58:34AM +0100, J=C3=BCrgen Gro=C3=9F wrot= e: >>>>> On 22.03.21 06:39, Leon Romanovsky wrote: >>>>>> On Sun, Mar 21, 2021 at 06:54:52PM +0100, Hsu, Chiahao wrote: >>>>>> <...> >>>>>> >>>>>>>>> Typically there should be one VM running netback on each host, >>>>>>>>> and having control over what interfaces or features it exposes = >>>>>>>>> is also >>>>>>>>> important for stability. >>>>>>>>> How about we create a 'feature flags' modparam, each bits is=20 >>>>>>>>> specified 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=20 >>>>>>> flag before >>>>>>> they use it. >>>>>>> For example, before user try to set/clear this ctrl_ring_enabled,= =20 >>>>>>> they >>>>>>> should already have basic knowledge about this feature, >>>>>>> or else they shouldn't use it (the default value is same as=20 >>>>>>> before), and >>>>>>> that's also why we use the 'ctrl_ring_enabled' as parameter name.= >>>>>> 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. >>>>>> >>>>>> In your flow, you want that users will set all module parameters f= or >>>>>> every upgrade and keep those parameters differently per-version. >>>>> I think the flag should be a per guest config item. Adding this=20 >>>>> item to >>>>> the backend Xenstore nodes for netback to consume it should be rath= er >>>>> 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= =2E >>>> Yes, it will overcome global nature of module parameters, but how do= es >>>> it solve backward compatibility concern? >>> When creating a guest on A the (unknown) feature will not be set to >>> any value in the guest's config data. A migration stream not having a= ny >>> value for that feature on B should set it to "false". >>> >>> When creating a guest on B it will either have the feature value set >>> explicitly in the guest config (either true or false), or it will get= >>> the server's default (this value should be configurable in a global >>> config file, default for that global value would be "true"). >>> >>> So with the guest created on B with feature specified as "false" (eit= her >>> for this guest only, or per global config), it will be migratable to >>> machine A without problem. Migrating it back to B would work the same= >>> way as above. Trying to migrate a guest with feature set to "true" to= >>> B would not work, but this would be the host admin's fault due to not= >>> configuring the guest correctly. > so the expected changes would be >=20 > 1. remove feature-ctrl-ring & feature-dynamic-multicast-control from=20 > netback_probe( ) > 2. consume the backend Xenstore nodes in connect( ) to see if Xen tools= =20 > set nodes(true/false) or not(unknown) Yes. I think this is the way to go. 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