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=-4.1 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 7E197C433E5 for ; Tue, 21 Jul 2020 07:06:22 +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 4721B21702 for ; Tue, 21 Jul 2020 07:06:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="HisOa32H" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4721B21702 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]:58544 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jxmM1-0005bz-IK for qemu-devel@archiver.kernel.org; Tue, 21 Jul 2020 03:06:21 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:36404) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jxmL9-0004p2-C5 for qemu-devel@nongnu.org; Tue, 21 Jul 2020 03:05:27 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:57449 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jxmL7-00017C-Qb for qemu-devel@nongnu.org; Tue, 21 Jul 2020 03:05:27 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1595315125; 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=kXIABjJzir6vJLp4Jsf94FB0ty9gB3NwlhdUDzO5hxY=; b=HisOa32HZrCQYVEsIOrnXXzKLAgSKwFcOvIZa7Kzv+vbzUHET3SeOI/jwtmSaLh6AXmNMC IYXYc9LmJvd0HNwf59cjsZL6rDV+weU/kaEMPlV0xJIqfQdHWNJPC39Ye3pKJFha9iTNZk 9U9HT3ykwjrwrYYGLApGIz3vKAODolk= 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-33-oWCFghNnOJaMR5_HUdlOpA-1; Tue, 21 Jul 2020 03:05:21 -0400 X-MC-Unique: oWCFghNnOJaMR5_HUdlOpA-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 EFFE618C63C0; Tue, 21 Jul 2020 07:05:19 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-112-143.ams2.redhat.com [10.36.112.143]) by smtp.corp.redhat.com (Postfix) with ESMTPS id DE11B60BF1; Tue, 21 Jul 2020 07:05:16 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 7B4FC111CA27; Tue, 21 Jul 2020 09:05:15 +0200 (CEST) From: Markus Armbruster To: "Michael S. Tsirkin" Subject: Re: Intended purpose of virtio-rng's QOM link "rng"? References: <87d04qfco3.fsf@dusky.pond.sub.org> <20200720112838-mutt-send-email-mst@kernel.org> Date: Tue, 21 Jul 2020 09:05:15 +0200 In-Reply-To: <20200720112838-mutt-send-email-mst@kernel.org> (Michael S. Tsirkin's message of "Mon, 20 Jul 2020 11:56:32 -0400") Message-ID: <87mu3tbb6c.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=armbru@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=207.211.31.120; envelope-from=armbru@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/21 01:46:39 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action 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: Halil Pasic , Christian Borntraeger , Cornelia Huck , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" "Michael S. Tsirkin" writes: > On Mon, Jul 20, 2020 at 05:07:08PM +0200, Markus Armbruster wrote: >> What is the intended purpose of object_property_set_link() in >> >> static void virtio_rng_pci_realize(VirtIOPCIProxy *vpci_dev, Error **errp) >> { >> VirtIORngPCI *vrng = VIRTIO_RNG_PCI(vpci_dev); >> DeviceState *vdev = DEVICE(&vrng->vdev); >> >> if (!qdev_realize(vdev, BUS(&vpci_dev->bus), errp)) { >> return; >> } >> >> object_property_set_link(OBJECT(vrng), "rng", OBJECT(vrng->vdev.conf.rng), >> NULL); >> } >> >> ? >> >> I'm asking because the function *always* fails. I believe it's been >> failing for years. >> >> Similar code in the CCW buddy. Also virtio-crypto-pci and >> virtio-crypto-ccw link "cryptodev". >> >> I tried moving it before qdev_realize(), where it doesn't fail. But >> then *I* fail, namely at finding any effect in QOM. > > I suspect that's because there's already a link with that name > created by virtio core. Is that right? Looks like it, in virtio_rng_device_realize(): if (vrng->conf.rng == NULL) { ... make up @default_backend ... object_property_set_link(OBJECT(dev), "rng", default_backend, &error_abort); } The object_property_set_link actually sets vrng->vdev.conf.rng (but it takes quite some digging to see that; MICAHI[*] at work). For virtio-crypto, the link is vcrypto->vdev.conf.cryptodev. virtio_crypto_pci_realize() first checks its already set: if (vcrypto->vdev.conf.cryptodev == NULL) { error_setg(errp, "'cryptodev' parameter expects a valid object"); return; } >> If it's really useless, I'll send a patch to drop it. All four are useless; will send patches. >> If it has a use, tell me more, so I can test my patch to move it. Thanks! [*] Make It Complicated And Hide It.