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=-4.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 A45ADC46466 for ; Mon, 5 Oct 2020 16:01:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 726092068E for ; Mon, 5 Oct 2020 16:01:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="PP+m1cjH" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727335AbgJEQB0 (ORCPT ); Mon, 5 Oct 2020 12:01:26 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:58002 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727204AbgJEQBZ (ORCPT ); Mon, 5 Oct 2020 12:01:25 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1601913684; 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=WzM75OJ7dMVOtSH9g1wN1IBCIBR91LOKcFE/xZZuN3E=; b=PP+m1cjHHxMXtHQTM9HqWBX4DkKYpoRHX3ubPH63vJDQu93fotrwySi3ckmtaR9BCMqZo0 dn7OuK+Bk+9B9bR4e8vvOB3Zx2FmLoG2+KY0+WXi/OabFhbnlYicL7srHSBwnFXIQBUjpD z/biTB21zBxAg/DKJsBeTy6UQ/GXRME= 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-24-8PACy3Q2Nu-ACd69Gp7OEA-1; Mon, 05 Oct 2020 12:01:18 -0400 X-MC-Unique: 8PACy3Q2Nu-ACd69Gp7OEA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 4885C107ACF7; Mon, 5 Oct 2020 16:01:16 +0000 (UTC) Received: from gondolin (ovpn-112-191.ams2.redhat.com [10.36.112.191]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5DCCB60C84; Mon, 5 Oct 2020 16:01:10 +0000 (UTC) Date: Mon, 5 Oct 2020 18:01:07 +0200 From: Cornelia Huck To: Matthew Rosato Cc: Alex Williamson , schnelle@linux.ibm.com, pmorel@linux.ibm.com, borntraeger@de.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, gerald.schaefer@linux.ibm.com, linux-s390@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 3/5] vfio-pci/zdev: define the vfio_zdev header Message-ID: <20201005180107.5d027441.cohuck@redhat.com> In-Reply-To: <8a71af3b-f8fc-48b2-45c6-51222fd2455b@linux.ibm.com> References: <1601668844-5798-1-git-send-email-mjrosato@linux.ibm.com> <1601668844-5798-4-git-send-email-mjrosato@linux.ibm.com> <20201002154417.20c2a7ef@x1.home> <8a71af3b-f8fc-48b2-45c6-51222fd2455b@linux.ibm.com> Organization: Red Hat GmbH MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 5 Oct 2020 09:52:25 -0400 Matthew Rosato wrote: > On 10/2/20 5:44 PM, Alex Williamson wrote: > > Can you discuss why a region with embedded capability chain is a better > > solution than extending the VFIO_DEVICE_GET_INFO ioctl to support a > > capability chain and providing this info there? This all appears to be > > read-only info, so what's the benefit of duplicating yet another > > It is indeed read-only info, and the device region was defined as such. > > I would not necessarily be opposed to extending VFIO_DEVICE_GET_INFO > with these defined as capabilities; I'd say a primary motivating factor > to putting these in their own region was to avoid stuffing a bunch of > s390-specific capabilities into a general-purpose ioctl response. Can't you make the zdev code register the capabilities? That would put them nicely into their own configurable part. > > But if you're OK with that notion, I can give that a crack in v3. > > > capability chain in a region? It would also be possible to define four > > separate device specific regions, one for each of these capabilities > > rather than creating this chain. It just seems like a strange approach > > I'm not sure if creating separate regions would be the right approach > though; these are just the first 4. There will definitely be additional > capabilities in support of new zPCI features moving forward, I'm not > sure how many regions we really want to end up with. Some might be as > small as a single field, which seems more in-line with capabilities vs > an entire region. If we are expecting more of these in the future, going with GET_INFO capabilities when adding new ones seems like the best approach.