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,DKIMWL_WL_HIGH, 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 458C1C433ED for ; Fri, 16 Apr 2021 14:26:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 07FB3610C8 for ; Fri, 16 Apr 2021 14:26:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235763AbhDPO1F (ORCPT ); Fri, 16 Apr 2021 10:27:05 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:37965 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233606AbhDPO1E (ORCPT ); Fri, 16 Apr 2021 10:27:04 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618583199; 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=t1Hv2NbQ/MlDR82Y8nOIlqSLTEiVX08oupchgjJ9jRA=; b=O1rjioiI59LvC+S4nBSeMhvzoA5ceS7spb7jFCdkjrRNpFC6fI2SWlI3K6TOtlvalhf1eK N8JyO3WbCICOTkpav9TbWyRS8TN7sLxljNHIGja8vud0uQjveKKbJMfRJFUsKy+0WG39bV fUYD+aLmoTlKKHb4d/5H4oRLVS0daMQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-125-Zj04weCaOsqjgL2F0OCe8Q-1; Fri, 16 Apr 2021 10:26:35 -0400 X-MC-Unique: Zj04weCaOsqjgL2F0OCe8Q-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C4FE0BBEE4; Fri, 16 Apr 2021 14:26:32 +0000 (UTC) Received: from [10.36.113.21] (ovpn-113-21.ams2.redhat.com [10.36.113.21]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 321F25D9C0; Fri, 16 Apr 2021 14:26:21 +0000 (UTC) Subject: Re: [PATCH V4 05/18] iommu/ioasid: Redefine IOASID set and allocation APIs To: Jason Gunthorpe Cc: "Liu, Yi L" , Jean-Philippe Brucker , "Tian, Kevin" , Jacob Pan , LKML , Joerg Roedel , Lu Baolu , David Woodhouse , "iommu@lists.linux-foundation.org" , "cgroups@vger.kernel.org" , Tejun Heo , Li Zefan , Johannes Weiner , Jean-Philippe Brucker , Alex Williamson , Jonathan Corbet , "Raj, Ashok" , "Wu, Hao" , "Jiang, Dave" References: <20210401134236.GF1463678@nvidia.com> <20210401160337.GJ1463678@nvidia.com> <4bea6eb9-08ad-4b6b-1e0f-c97ece58a078@redhat.com> <20210415230732.GG1370958@nvidia.com> <20210416140524.GI1370958@nvidia.com> From: Auger Eric Message-ID: Date: Fri, 16 Apr 2021 16:26:19 +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: <20210416140524.GI1370958@nvidia.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 4/16/21 4:05 PM, Jason Gunthorpe wrote: > On Fri, Apr 16, 2021 at 03:38:02PM +0200, Auger Eric wrote: > >> The redesign requirement came pretty late in the development process. >> The iommu user API is upstream for a while, the VFIO interfaces have >> been submitted a long time ago and under review for a bunch of time. >> Redesigning everything with a different API, undefined at this point, is >> a major setback for our work and will have a large impact on the >> introduction of features companies are looking forward, hence our >> frustration. > > I will answer both you and Jacob at once. > > This is uAPI, once it is set it can never be changed. > > The kernel process and philosophy is to invest heavily in uAPI > development and review to converge on the best uAPI possible. > > Many past submissions have take a long time to get this right, there > are several high profile uAPI examples. > > Do you think this case is so special, or the concerns so minor, that it > should get to bypass all of the normal process? That's not my intent to bypass any process. I am just trying to understand what needs to be re-designed and for what use case. > > Ask yourself, is anyone advocating for the current direction on > technical merits alone? > > Certainly the patches I last saw where completely disgusting from a > uAPI design perspective. > > It was against the development process to organize this work the way > it was done. Merging a wack of dead code to the kernel to support a > uAPI vision that was never clearly articulated was a big mistake. > > Start from the beginning. Invest heavily in defining a high quality > uAPI. Clearly describe the uAPI to all stake holders. This was largely done during several confs including plumber, KVM forum, for several years. Also API docs were shared on the ML. I don't remember any voice was raised at those moments. Break up the > implementation into patch series without dead code. Make the > patches. Remove the dead code this group has already added. > > None of this should be a surprise. The VDPA discussion and related > "what is a mdev" over a year ago made it pretty clear VFIO is not the > exclusive user of "IOMMU in userspace" and that places limits on what > kind of uAPIs expansion it should experience going forward. Maybe clear for you but most probably not for many other stakeholders. Anyway I do not intend to further argue and I will be happy to learn from you and work with you, Jacob, Liu and all other stakeholders to define a better integration. Thanks Eric > > Jason >