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 C517FC3DA49 for ; Fri, 2 Aug 2024 08:02:08 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sZnEE-0008Jh-RS; Fri, 02 Aug 2024 04:01:34 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sZnEC-0008Ig-Mn for qemu-devel@nongnu.org; Fri, 02 Aug 2024 04:01:32 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sZnEA-0004xy-CF for qemu-devel@nongnu.org; Fri, 02 Aug 2024 04:01:32 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1722585688; 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=u/sTUvm1SB+z7dTfDlvvhnjSHGNpwLqP2R3D/TauNp4=; b=MRU/B3E8Ggw92OlRjAUKeS47bg2ORBh8SlwPZOrGElOyZ5w64KxuzwAXcsMDUSpjcBrh6y bvAk72LybqqG4ZuZFThu9n42fjyZwn7PgzvMB3AheKJFa+mO3iQQ7mRtFRID2+drj6ivSE JgFJfPtxJpY/pfoJofdnM+aNY9foz8M= Received: from mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-99-5XTNc4Y5O4mPUY-wUXPyBg-1; Fri, 02 Aug 2024 04:01:25 -0400 X-MC-Unique: 5XTNc4Y5O4mPUY-wUXPyBg-1 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 8A094195421A; Fri, 2 Aug 2024 08:01:24 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.65]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id CBF60300018D; Fri, 2 Aug 2024 08:01:22 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 9085421E6682; Fri, 2 Aug 2024 10:01:20 +0200 (CEST) From: Markus Armbruster To: Stefan Hajnoczi Cc: qemu-devel@nongnu.org, Paolo Bonzini , Eduardo Habkost , pkrempa@redhat.com, Daniel P. =?utf-8?Q?Berrang=C3=A9?= Subject: Re: [PATCH v2 1/2] qdev-monitor: avoid QemuOpts in QMP device_add In-Reply-To: <20240801140552.1021693-2-stefanha@redhat.com> (Stefan Hajnoczi's message of "Thu, 1 Aug 2024 10:05:51 -0400") References: <20240801140552.1021693-1-stefanha@redhat.com> <20240801140552.1021693-2-stefanha@redhat.com> Date: Fri, 02 Aug 2024 10:01:20 +0200 Message-ID: <875xsj73qn.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.131, 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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=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: 2.1.29 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-bounces+qemu-devel=archiver.kernel.org@nongnu.org Stefan Hajnoczi writes: > The QMP device_add monitor command converts the QDict arguments to > QemuOpts and then back again to QDict. This process only supports scalar > types. Device properties like virtio-blk-pci's iothread-vq-mapping (an > array of objects) are silently dropped by qemu_opts_from_qdict() during > the QemuOpts conversion even though QAPI is capable of validating them. > As a result, hotplugging virtio-blk-pci devices with the > iothread-vq-mapping property does not work as expected (the property is > ignored). > > Get rid of the QemuOpts conversion in qmp_device_add() and call > qdev_device_add_from_qdict() with from_json=3Dtrue. Using the QMP > command's QDict arguments directly allows non-scalar properties. > > The HMP is also adjusted since qmp_device_add()'s now expects properly > typed JSON arguments and cannot be used from HMP anymore. Move the code > that was previously in qmp_device_add() (with QemuOpts conversion and > from_json=3Dfalse) into hmp_device_add() so that its behavior is > unchanged. > > This patch changes the behavior of QMP device_add but not HMP > device_add. QMP clients that sent incorrectly typed device_add QMP > commands no longer work. This is a breaking change but clients should be > using the correct types already. See the netdev_add QAPIfication in > commit db2a380c8457 for similar reasoning and object-add in commit > 9151e59a8b6e. Unlike those commits, we continue to rely on 'gen': false > for the time being. > > Move the drain_call_rcu() invocation into qdev_device_add_from_qdict() > so all callers benefit from it automatically. This avoids code > duplication. > > Markus helped me figure this out and even provided a draft patch. The > code ended up very close to what he suggested. > > Suggested-by: Markus Armbruster > Cc: Daniel P. Berrang=C3=A9 > Signed-off-by: Stefan Hajnoczi > --- > system/qdev-monitor.c | 56 ++++++++++++++++++++++--------------------- > 1 file changed, 29 insertions(+), 27 deletions(-) > > diff --git a/system/qdev-monitor.c b/system/qdev-monitor.c > index 6af6ef7d66..8a756b1a91 100644 > --- a/system/qdev-monitor.c > +++ b/system/qdev-monitor.c > @@ -725,6 +725,17 @@ err_del_dev: > if (dev) { > object_unparent(OBJECT(dev)); > object_unref(OBJECT(dev)); > + > + /* > + * Drain all pending RCU callbacks. This is done because > + * some bus related operations can delay a device removal > + * (in this case this can happen if device is added and then > + * removed due to a configuration error) > + * to a RCU callback, but user might expect that this interface > + * will finish its job completely once qmp command returns result > + * to the user > + */ > + drain_call_rcu(); > } > return NULL; > } Moving this from qmp_device_add() adds RCU draining to call chains not going through qmp_device_add(). Can adding it hurt? I guess it can't. Can it fix bugs? I don't know. Let's review the callers of qdev_device_add_from_qdict(): * qdev_device_add() - called from qmp_device_add() No change. - called from device_init_func() called from qemu_create_cli_devices() See below. - called from usbback_portid_add() called from usbback_process_port() called from usbback_backend_changed() =C2=B7 called from usbback_init() =C2=B7 called as XenDevOps method backend_changed() This is Xen. We now drain pending RCU callbacks. Impact? Beats me. * qemu_create_cli_devices() called from qmp_x_exit_preconfig() - as QMP command with -preconfig, phase must be PHASE_MACHINE_INITIALIZED - called from qemu_init() without -preconfig We now drain pending RCU callbacks. Can any be pending at this early point? If not, the change is a no-op. * failover_add_primary() called from virtio_net_set_features() called as VirtioDeviceClass method set_features() This is virtio-net failover. We now drain pending RCU callbacks. Impact? Beats me. My gut feeling is "improvement, possibly even a bug fix". It deserves its own commit, doesn't it? > @@ -849,34 +860,10 @@ void hmp_info_qdm(Monitor *mon, const QDict *qdict) >=20=20 > void qmp_device_add(QDict *qdict, QObject **ret_data, Error **errp) > { > - QemuOpts *opts; > DeviceState *dev; >=20=20 > - opts =3D qemu_opts_from_qdict(qemu_find_opts("device"), qdict, errp); > - if (!opts) { > - return; > - } > - if (!monitor_cur_is_qmp() && qdev_device_help(opts)) { > - qemu_opts_del(opts); > - return; > - } > - dev =3D qdev_device_add(opts, errp); > - if (!dev) { > - /* > - * Drain all pending RCU callbacks. This is done because > - * some bus related operations can delay a device removal > - * (in this case this can happen if device is added and then > - * removed due to a configuration error) > - * to a RCU callback, but user might expect that this interface > - * will finish its job completely once qmp command returns result > - * to the user > - */ > - drain_call_rcu(); > - > - qemu_opts_del(opts); > - return; > - } > - object_unref(OBJECT(dev)); > + dev =3D qdev_device_add_from_qdict(qdict, true, errp); > + object_unref(dev); > } >=20=20 > static DeviceState *find_device_state(const char *id, Error **errp) > @@ -967,8 +954,23 @@ void qmp_device_del(const char *id, Error **errp) > void hmp_device_add(Monitor *mon, const QDict *qdict) > { > Error *err =3D NULL; > + QemuOpts *opts; > + DeviceState *dev; >=20=20 > - qmp_device_add((QDict *)qdict, NULL, &err); > + opts =3D qemu_opts_from_qdict(qemu_find_opts("device"), qdict, &err); > + if (!opts) { > + goto out; > + } > + if (qdev_device_help(opts)) { > + qemu_opts_del(opts); > + return; > + } > + dev =3D qdev_device_add(opts, &err); > + if (!dev) { > + qemu_opts_del(opts); > + } > + object_unref(dev); > +out: > hmp_handle_error(mon, err); > } Remainder looks good to me.