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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CF95CC433EF for ; Tue, 5 Oct 2021 15:05:40 +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 44566613AC for ; Tue, 5 Oct 2021 15:05:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 44566613AC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:53880 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mXm0h-0002og-Bz for qemu-devel@archiver.kernel.org; Tue, 05 Oct 2021 11:05:39 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:54436) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mXlaA-00005S-LN for qemu-devel@nongnu.org; Tue, 05 Oct 2021 10:38:14 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:48767) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mXla8-0007PK-Lz for qemu-devel@nongnu.org; Tue, 05 Oct 2021 10:38:14 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1633444691; 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=w3qBCN3qgXQmu2+h2E+UziQNNWRxZWvrSOkNo/LO4tM=; b=Z4t5WJrj9abamRjgqID3dqh5YsudKEvD0JPTMESdg7sK6U29eWg0Y6nPeyS/xUiR/XkXAC Tci8AkhpDs46wlmxdcqw4PHgGsTValDIZN+HY6/IOIndiDnwBB2vhUba3OwKL9/blWzsA9 QMS5dGWN0KvZgGWMPdyeSLflLubJOhQ= 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-558-k7imYVoXOd2wXRrWpZ-PJA-1; Tue, 05 Oct 2021 10:37:56 -0400 X-MC-Unique: k7imYVoXOd2wXRrWpZ-PJA-1 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 mimecast-mx01.redhat.com (Postfix) with ESMTPS id A8ED18064A5; Tue, 5 Oct 2021 14:37:54 +0000 (UTC) Received: from redhat.com (unknown [10.39.193.80]) by smtp.corp.redhat.com (Postfix) with ESMTPS id DDADF1F451; Tue, 5 Oct 2021 14:37:34 +0000 (UTC) Date: Tue, 5 Oct 2021 16:37:33 +0200 From: Kevin Wolf To: Damien Hedde Subject: Re: [PATCH 09/11] qdev: Avoid QemuOpts in QMP device_add Message-ID: References: <20210924090427.9218-1-kwolf@redhat.com> <20210924090427.9218-10-kwolf@redhat.com> <89bbeed4-dec6-007a-175e-38a12e5bbfa1@greensocs.com> MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=170.10.133.124; envelope-from=kwolf@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=-0.066, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, 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: lvivier@redhat.com, pkrempa@redhat.com, berrange@redhat.com, ehabkost@redhat.com, qemu-block@nongnu.org, mst@redhat.com, libvir-list@redhat.com, quintela@redhat.com, qemu-devel@nongnu.org, armbru@redhat.com, its@irrelevant.dk, pbonzini@redhat.com, jfreimann@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 27.09.2021 um 13:39 hat Kevin Wolf geschrieben: > Am 27.09.2021 um 13:06 hat Damien Hedde geschrieben: > > On 9/24/21 11:04, Kevin Wolf wrote: > > > Directly call qdev_device_add_from_qdict() for QMP device_add instead of > > > first going through QemuOpts and converting back to QDict. > > > > > > Note that this changes the behaviour of device_add, though in ways that > > > should be considered bug fixes: > > > > > > QemuOpts ignores differences between data types, so you could > > > successfully pass a string "123" for an integer property, or a string > > > "on" for a boolean property (and vice versa). After this change, the > > > correct data type for the property must be used in the JSON input. > > > > > > qemu_opts_from_qdict() also silently ignores any options whose value is > > > a QDict, QList or QNull. > > > > > > To illustrate, the following QMP command was accepted before and is now > > > rejected for both reasons: > > > > > > { "execute": "device_add", > > > "arguments": { "driver": "scsi-cd", > > > "drive": { "completely": "invalid" }, > > > "physical_block_size": "4096" } } > > > > > > Signed-off-by: Kevin Wolf > > > --- > > > softmmu/qdev-monitor.c | 18 +++++++++++------- > > > 1 file changed, 11 insertions(+), 7 deletions(-) > > > > > > diff --git a/softmmu/qdev-monitor.c b/softmmu/qdev-monitor.c > > > index c09b7430eb..8622ccade6 100644 > > > --- a/softmmu/qdev-monitor.c > > > +++ b/softmmu/qdev-monitor.c > > > @@ -812,7 +812,8 @@ void hmp_info_qdm(Monitor *mon, const QDict *qdict) > > > qdev_print_devinfos(true); > > > } > > > -void qmp_device_add(QDict *qdict, QObject **ret_data, Error **errp) > > > +static void monitor_device_add(QDict *qdict, QObject **ret_data, > > > + bool from_json, Error **errp) > > > { > > > QemuOpts *opts; > > > DeviceState *dev; > > > @@ -825,7 +826,9 @@ void qmp_device_add(QDict *qdict, QObject **ret_data, Error **errp) > > > qemu_opts_del(opts); > > > return; > > > } > > > - dev = qdev_device_add(opts, errp); > > > + qemu_opts_del(opts); > > > + > > > + dev = qdev_device_add_from_qdict(qdict, from_json, errp); > > > > Hi Kevin, > > > > I'm wandering if deleting the opts (which remove it from the "device" opts > > list) is really a no-op ? > > It's not exactly a no-op. Previously, the QemuOpts would only be freed > when the device is destroying, now we delete it immediately after > creating the device. This could matter in some cases. > > The one case I was aware of is that QemuOpts used to be responsible for > checking for duplicate IDs. Obviously, it can't do this job any more > when we call qemu_opts_del() right after creating the device. This is > the reason for patch 6. > > > The opts list is, eg, traversed in hw/net/virtio-net.c in the function > > failover_find_primary_device_id() which may be called during the > > virtio_net_set_features() (a TYPE_VIRTIO_NET method). > > I do not have the knowledge to tell when this method is called. But If this > > is after we create the devices. Then the list will be empty at this point > > now. > > > > It seems, there are 2 other calling sites of > > "qemu_opts_foreach(qemu_find_opts("device"), [...]" in net/vhost-user.c and > > net/vhost-vdpa.c > > Yes, you are right. These callers probably need to be changed. Going > through the command line options rather than looking at the actual > device objects that exist doesn't feel entirely clean anyway. So I tried to have a look at the virtio-net case, and ended up very confused. Obviously looking at command line options (even of a differrent device) from within a device is very unclean. With a non-broken, i.e. type safe, device-add (as well as with the JSON CLI option introduced by this series), we can't have a QemuOpts any more that is by definition unsafe. So this code needs a replacement. My naive idea was that we just need to look at runtime state instead. Don't search the options for a device with a matching 'failover_pair_id' (which, by the way, would fail as soon as any other device introduces a property with the same name), but search for actual PCIDevices in qdev that have pci_dev->failover_pair_id set accordingly. However, the logic in failover_add_primary() suggests that we can have a state where QemuOpts for a device exist, but the device doesn't, and then it hotplugs the device from the command line options. How would we ever get into such an inconsistent state where QemuOpts contains a device that doesn't exist? Normally devices get their QemuOpts when they are created and device_finalize() deletes the QemuOpts again. Any suggestions how to get rid of the QemuOpts abuse in the failover code? If this is a device that we previously managed to rip out without deleting its QemuOpts, can we store its dev->opts (which is a type safe QDict after this series) somewhere locally instead of looking at global state? Preferably I would even like to get rid of dev->opts because we really should look at live state rather than command line options after device creation, but I guess one step at a time. (Actually, I'm half tempted to just break it because no test cases seem to exist, so apparently nobody is really interested in it.) Kevin