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=-0.8 required=3.0 tests=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 1C9C0C0650F for ; Tue, 30 Jul 2019 11:37:11 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 E299E206E0 for ; Tue, 30 Jul 2019 11:37:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E299E206E0 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:59938 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hsQRK-0008Q3-7U for qemu-devel@archiver.kernel.org; Tue, 30 Jul 2019 07:37:10 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:54367) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hsQQ8-000762-Bs for qemu-devel@nongnu.org; Tue, 30 Jul 2019 07:35:57 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hsQQ7-0004NQ-C9 for qemu-devel@nongnu.org; Tue, 30 Jul 2019 07:35:56 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51452) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hsQQ7-0004NC-6E for qemu-devel@nongnu.org; Tue, 30 Jul 2019 07:35:55 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6C04C3092649; Tue, 30 Jul 2019 11:35:54 +0000 (UTC) Received: from gondolin (dhcp-192-232.str.redhat.com [10.33.192.232]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7CBC319C67; Tue, 30 Jul 2019 11:35:48 +0000 (UTC) Date: Tue, 30 Jul 2019 13:35:46 +0200 From: Cornelia Huck To: Andrea Bolognani Message-ID: <20190730133546.056f8b19.cohuck@redhat.com> In-Reply-To: References: <20190729125755.45008-1-slp@redhat.com> Organization: Red Hat GmbH MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.43]); Tue, 30 Jul 2019 11:35:54 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [RFC] virtio-mmio: implement modern (v2) personality (virtio-1) X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: peter.maydell@linaro.org, qemu-devel@nongnu.org, Sergio Lopez , mst@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, 30 Jul 2019 12:25:30 +0200 Andrea Bolognani wrote: > On Mon, 2019-07-29 at 14:57 +0200, Sergio Lopez wrote: > [...] > > /* virtio-mmio device */ > > > > static Property virtio_mmio_properties[] = { > > DEFINE_PROP_BOOL("format_transport_address", VirtIOMMIOProxy, > > format_transport_address, true), > > + DEFINE_PROP_BOOL("modern", VirtIOMMIOProxy, modern, false), > > DEFINE_PROP_END_OF_LIST(), > > }; > > Not a QEMU developer so forgive me if I say something silly, but IIUC > you'd be able to opt into the new feature by using eg. > > -device virtio-net-device,modern=on > > However, virtio-pci devices already have a mechanism to control the > VirtIO protocol version, where you use > > -device virtio-net-pci,disable-modern=no,disable-legacy=yes > > to get a VirtIO 1.x-only device and > > -device virtio-net-pci,disable-modern=no,disable-legacy=no > > for a transitional device. > > Can you please make sure virtio-mmio uses the existing interface > instead of introducing a new one? > FWIW, I really hate virtio-pci's disable-modern/disable-legacy... for a starter, what is 'modern'? Will we have 'ultra-modern' in the future? It is also quite backwards with the 'disable' terminology. We also have a different mechanism for virtio-ccw ('max_revision', which covers a bit more than virtio-1; it doesn't have a 'min_revision', as negotiating the revision down is fine), so I don't see why virtio-mmio should replicate the virtio-pci mechanism. Also, IIUC, virtio-mmio does not have transitional devices, but either version 1 (legacy) or version 2 (virtio-1). It probably makes more sense to expose the device version instead; either as an exact version (especially if it isn't supposed to go up without incompatible changes), or with some min/max concept (where version 1 would stand a bit alone, so that would probably be a bit awkward.)