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=-11.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 9B6D9C47089 for ; Wed, 26 May 2021 14:34:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7D540611CD for ; Wed, 26 May 2021 14:34:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234784AbhEZOgD (ORCPT ); Wed, 26 May 2021 10:36:03 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:58424 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234694AbhEZOgB (ORCPT ); Wed, 26 May 2021 10:36:01 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1622039669; 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=cqBPgPyUlAbZ7Kk+oGgbHiAKQDgT/aGEeIFiCp5+zq4=; b=Z7JqM08OFktzokQsVJFJPz4qA/0FVcsIKa2K7nDkn+dKbmDctbQ+JCAppNnGZQ4xI+LOO7 LR47e+F1Dp0nWIIotkMq18nTt5uTZh99vZh6mho3IWmA6ZJMt62Fj6JdLnBYv7TS9ROywa utL93K+A8xXIV8v6koCQc+ASqyfJeuw= 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-384-D2hxjXQtPpStZr2pCmQUGA-1; Wed, 26 May 2021 10:34:25 -0400 X-MC-Unique: D2hxjXQtPpStZr2pCmQUGA-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 3911A107AD35; Wed, 26 May 2021 14:34:24 +0000 (UTC) Received: from gondolin.fritz.box (ovpn-113-79.ams2.redhat.com [10.36.113.79]) by smtp.corp.redhat.com (Postfix) with ESMTP id C85BA1037F21; Wed, 26 May 2021 14:34:22 +0000 (UTC) Date: Wed, 26 May 2021 16:34:20 +0200 From: Cornelia Huck To: Halil Pasic , "Michael S. Tsirkin" , Jason Wang Cc: linux-s390@vger.kernel.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org Subject: Re: [PATCH RFC 0/2] virtio-ccw: allow to disable legacy virtio Message-ID: <20210526163420.4620f342.cohuck@redhat.com> In-Reply-To: <20210304132715.1587211-1-cohuck@redhat.com> References: <20210304132715.1587211-1-cohuck@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 10.5.11.22 Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org On Thu, 4 Mar 2021 14:27:13 +0100 Cornelia Huck wrote: Just found this old series sitting there... does anyone have an opinion on the general approach? > Unlike virtio-pci, virtio-ccw is currently always a transitional > driver (i.e. it always includes support for legacy devices.) The > differences between legacy and virtio-1+ virtio-ccw devices are not > that big (the most interesting things are in common virtio code > anyway.) > > It might be beneficial to make support for legacy virtio generally > configurable, in case we want to remove it completely in a future > where we all have flying cars. As a prereq, we need to make it > configurable for virtio-ccw. > > Patch 1 introduces a parameter; now that I look at it, it's probably > not that useful (not even for testing), so I'm inclined to drop it > again. > > Patch 2 adds a new config symbol for generic legacy virtio support, > which currently does not do anything but being selected by the > legacy options for virtio-pci and virtio-ccw. A virtio-ccw driver > without legacy support will require a revision of 1 or higher to > be supported by the device. > > A virtio-ccw driver with legacy turned off works well for me with > transitional devices and fails onlining gracefully for legacy devices > (max_revision=0 in QEMU). > > (I also have some code that allows to make devices non-transitional > in QEMU, but I haven't yet found time to polish the patches.) > > Cornelia Huck (2): > virtio/s390: add parameter for minimum revision > virtio/s390: make legacy support configurable > > arch/s390/Kconfig | 11 ++ > drivers/s390/virtio/Makefile | 1 + > drivers/s390/virtio/virtio_ccw.c | 179 ++++++++---------------- > drivers/s390/virtio/virtio_ccw_common.h | 113 +++++++++++++++ > drivers/s390/virtio/virtio_ccw_legacy.c | 138 ++++++++++++++++++ > drivers/virtio/Kconfig | 8 ++ > 6 files changed, 330 insertions(+), 120 deletions(-) > create mode 100644 drivers/s390/virtio/virtio_ccw_common.h > create mode 100644 drivers/s390/virtio/virtio_ccw_legacy.c > > > base-commit: cf6acb8bdb1d829b85a4daa2944bf9e71c93f4b9