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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id B8900C43334 for ; Thu, 23 Jun 2022 10:19:48 +0000 (UTC) Received: from localhost ([::1]:33420 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1o4JwB-0003Y6-Hr for qemu-devel@archiver.kernel.org; Thu, 23 Jun 2022 06:19:47 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:53512) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1o4Jq7-00083p-Ms for qemu-devel@nongnu.org; Thu, 23 Jun 2022 06:13:31 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:34938) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1o4Jq3-0003ck-6g for qemu-devel@nongnu.org; Thu, 23 Jun 2022 06:13:30 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1655979206; 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: in-reply-to:in-reply-to:references:references; bh=GJsov3FRHExvTrVt+NnDWqd4nVtfkI9+w+0xLT0hCHo=; b=RjKZgDUuK7ZMR/HMGN1pqBRgGiqPcCBMyOUa8gsf9bTsP6o6MNux3wQCDWIeoL47Vd/k7h ywDeonA0U26kdsx5WMauVJQrAvfebzwxzD4INUm0IOMDxaSbif9e+pbqGG4lWLFzHZLlqO bAZDEg3p8sZtpFpDIrzvdua5/y9hpOg= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-251-kD77fO9fPdurIGvswOT3Aw-1; Thu, 23 Jun 2022 06:13:23 -0400 X-MC-Unique: kD77fO9fPdurIGvswOT3Aw-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id A316629DD9B8; Thu, 23 Jun 2022 10:13:22 +0000 (UTC) Received: from localhost (unknown [10.39.194.10]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5EE66C2810D; Thu, 23 Jun 2022 10:13:22 +0000 (UTC) From: Cornelia Huck To: Thomas Huth , qemu-s390x@nongnu.org, Christian Borntraeger , Eric Farman Cc: qemu-devel@nongnu.org Subject: Re: [PATCH 2/2] pc-bios/s390-ccw/virtio: Read device config after feature negotiation In-Reply-To: <749f88c5-379c-6284-f3c7-c8074191c8a9@redhat.com> Organization: Red Hat GmbH References: <20220623071131.412457-1-thuth@redhat.com> <20220623071131.412457-3-thuth@redhat.com> <87bkuj93b6.fsf@redhat.com> <749f88c5-379c-6284-f3c7-c8074191c8a9@redhat.com> User-Agent: Notmuch/0.36 (https://notmuchmail.org) Date: Thu, 23 Jun 2022 12:13:21 +0200 Message-ID: <878rpn8z7i.fsf@redhat.com> MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.85 on 10.11.54.8 Received-SPF: pass client-ip=170.10.129.124; envelope-from=cohuck@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Jun 23 2022, Thomas Huth wrote: > On 23/06/2022 10.44, Cornelia Huck wrote: >> On Thu, Jun 23 2022, Thomas Huth wrote: >> >>> Feature negotiation should be done first, since some fields in the >>> config area can depend on the negotiated features and thus should >>> rather be read afterwards. >> >> I suppose we don't negotiate any features that might affect the size of >> the config space? Anyway, restricting ourselves to the minimum length >> should be fine. > > Actually, even the virtio spec 0.9.5 already talks about > VIRTIO_BLK_F_BLK_SIZE and VIRTIO_BLK_F_GEOMETRY being necessary to get the > corresponding values in the config space ... so we're currently depending on > the good will of QEMU to also provide the values without these feature bits. Eww. The bad thing about QEMU being so relaxed is that you don't catch issues like that... but if it works for now, there's at least no pressure. > I'm already thinking about providing a patch to properly request these > feature bits in the s390-ccw bios ... but the whole code there is so ugly > that I need some time to think about the right steps to clean it up first. It's not ugly, it has grown organically :) (just like that overgrown spot in my garden ;)