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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 C7223C433E1 for ; Fri, 26 Jun 2020 17:46:51 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9AA3B207D8 for ; Fri, 26 Jun 2020 17:46:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=xen.org header.i=@xen.org header.b="aEVIYnOC" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9AA3B207D8 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=xen.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1josQh-0001rW-Kt; Fri, 26 Jun 2020 17:46:23 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1josQg-0001rP-4I for xen-devel@lists.xenproject.org; Fri, 26 Jun 2020 17:46:22 +0000 X-Inumbo-ID: f24575ca-b7d4-11ea-bb8b-bc764e2007e4 Received: from mail.xenproject.org (unknown [104.130.215.37]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id f24575ca-b7d4-11ea-bb8b-bc764e2007e4; Fri, 26 Jun 2020 17:46:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=xen.org; s=20200302mail; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:References:Cc:To:Subject:Sender:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=jt4yZmJG7KXUCRdT6sM646MFKXBc143aigS0EWKAcCw=; b=aEVIYnOCu7+qUj+0Ji7n3Y1OxN aQWQKi8N4hudQQRVKHs+pzMSvT2JbKJLvaRRzh6Csxelgs4IMQvMUt5c53gCW/RXxVIetzJHRn7UR UCrBiwEEwJy951V7a5UueEqqKlI9+dRE7mk3j+s6zQd9AhTcfIdxCRkrPwCWLaefXapg=; Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1josQZ-0001Ud-Ex; Fri, 26 Jun 2020 17:46:15 +0000 Received: from [54.239.6.185] (helo=a483e7b01a66.ant.amazon.com) by xenbits.xenproject.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1josQZ-0002LT-7a; Fri, 26 Jun 2020 17:46:15 +0000 Subject: Re: [PATCH v3 for-4.14] pvcalls: Document correctly and explicitely the padding for all arches To: Ian Jackson References: <20200613184132.11880-1-julien@xen.org> <35c8373f-b691-d95e-17de-021c72faf216@xen.org> <24307.16713.764272.855818@mariner.uk.xensource.com> From: Julien Grall Message-ID: <8335fa07-7610-2a40-36fc-49d6f900026c@xen.org> Date: Fri, 26 Jun 2020 18:46:12 +0100 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <24307.16713.764272.855818@mariner.uk.xensource.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Juergen Gross , Stefano Stabellini , Wei Liu , Paul Durrant , Andrew Cooper , Julien Grall , George Dunlap , "committers@xenproject.org" , Jan Beulich , xen-devel , Roger Pau Monne , Julien Grall Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" Hi Ian, Thank you for your input! On 24/06/2020 13:04, Ian Jackson wrote: > Julien Grall writes ("Re: [PATCH v3 for-4.14] pvcalls: Document correctly and explicitely the padding for all arches"): >> (+ Committers) > ... >> As Jan and you disagree on the approach, I would like to get more input. >> >> To summarize the discussion, the document for PV calls and the public >> headers don't match when describing the padding. There is a disagreement >> on which of the two are the authority and therefore which one to fix. >> >> Does anyone else have a preference on the approach? > > Hi. > >> [Jan:] >>> I am leaning towards the header as authoritative because this has >>> always been the case in the past and nothing in xen.git says >>> otherwise. However I am not a user of pvcalls, so I don't really have >>> any big incentive to go either way. > > I think the practice of using headers as protocol specs is not a > particularly good one. Certainly my expectations anywhere outside the > Xen Project is that if there's a doc, that is at the very least on par > with any header file. Of course there are possible compatibility > implications: > >> Yeah, we are risking breaking one set of users either way :-/ >> In reality, we are using pvcalls on arm64 in a new project (but it is >> still very green). I am not aware of anybody using pvcalls on x86 >> (especially x86_32). >> >> I would prefer to honor the pvcalls.pandoc specification because that is >> what it was meant to be, and also leads to a better protocol >> specification. > > pvcalls in Linux is Tech Preview / Experimental AFAICT ? I think that > means we can de jure change things like this. SUPPORT.md suggests this is a Tech Preview, so I agree that we could still change the interface. > > And it seems that we don't think there are any actual users who would > experience compatibility problems. Right, that's what Stefano suggested. > > So I don't think the compatibility concerns are a reason not to change > the header rather than the document. > > So I think my conclusion is the same as Julien's: we should change the > header to match the doc. Ok, so you are on the same page as Stefano. I will revert to the v1 change and rework the commit message then. > >>>> For the future, I would highly suggest writing down the support >>>> decision in xen.git. This would avoid such debate on what is the >>>> authority... >>> >>> Yes that's the way to go > > Maybe it would be worth putting a note somewhere in the headers saying > the headers are provided for convenience but that the ABIs and > protocols are as specified in the docs (at least where docs exist). I will write a patch for it. Cheers, -- Julien Grall