From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44205) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eEFHl-00084q-7e for qemu-devel@nongnu.org; Mon, 13 Nov 2017 09:00:30 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eEFHh-0003Gb-0U for qemu-devel@nongnu.org; Mon, 13 Nov 2017 09:00:25 -0500 Received: from mx1.redhat.com ([209.132.183.28]:43004) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eEFHg-0003GB-L0 for qemu-devel@nongnu.org; Mon, 13 Nov 2017 09:00:20 -0500 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B73CE7EA9A for ; Mon, 13 Nov 2017 14:00:19 +0000 (UTC) From: Markus Armbruster References: <1509617407-21191-1-git-send-email-thuth@redhat.com> <1509617407-21191-3-git-send-email-thuth@redhat.com> Date: Mon, 13 Nov 2017 15:00:03 +0100 In-Reply-To: <1509617407-21191-3-git-send-email-thuth@redhat.com> (Thomas Huth's message of "Thu, 2 Nov 2017 11:10:06 +0100") Message-ID: <87vaiecm8s.fsf@dusky.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Qemu-devel] [PATCH v3 2/2] qdev: Check for the availability of a hotplug controller before adding a device List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Thomas Huth Cc: qemu-devel@nongnu.org, Eduardo Habkost , Igor Mammedov , "Dr. David Alan Gilbert" , Paolo Bonzini , david@redhat.com Thomas Huth writes: > The qdev_unplug() function contains a g_assert(hotplug_ctrl) statement, > so QEMU crashes when the user tries to device_add + device_del a device > that does not have a corresponding hotplug controller. This could be > provoked for a couple of devices in the past (see commit 4c93950659487c7ad > or 84ebd3e8c7d4fe955 for example), and can currently for example also be > triggered like this: > > $ s390x-softmmu/qemu-system-s390x -M none -nographic > QEMU 2.10.50 monitor - type 'help' for more information > (qemu) device_add qemu-s390x-cpu,id=x > (qemu) device_del x > ** > ERROR:qemu/qdev-monitor.c:872:qdev_unplug: assertion failed: (hotplug_ctrl) > Aborted (core dumped) > > So devices clearly need a hotplug controller when they should be usable > with device_add. > The code in qdev_device_add() already checks whether the bus has a proper > hotplug controller, Where? Hmm, I guess it's this one: if (qdev_hotplug && bus && !qbus_is_hotpluggable(bus)) { error_setg(errp, QERR_BUS_NO_HOTPLUG, bus->name); return NULL; } > but for devices that do not have a corresponding bus, > there is no appropriate check available yet. In that case we should check > whether the machine itself provides a suitable hotplug controller and > refuse to plug the device if none is available. > > Reviewed-by: Igor Mammedov > Signed-off-by: Thomas Huth > --- > hw/core/qdev.c | 28 ++++++++++++++++++++-------- > include/hw/qdev-core.h | 1 + > qdev-monitor.c | 5 +++++ > 3 files changed, 26 insertions(+), 8 deletions(-) > > diff --git a/hw/core/qdev.c b/hw/core/qdev.c > index 1111295..f739753 100644 > --- a/hw/core/qdev.c > +++ b/hw/core/qdev.c > @@ -253,19 +253,31 @@ void qdev_set_legacy_instance_id(DeviceState *dev, int alias_id, > dev->alias_required_for_version = required_for_version; > } > > +HotplugHandler *qdev_get_machine_hotplug_handler(DeviceState *dev) > +{ > + MachineState *machine; > + MachineClass *mc; > + Object *m_obj = qdev_get_machine(); > + > + if (object_dynamic_cast(m_obj, TYPE_MACHINE)) { > + machine = MACHINE(m_obj); > + mc = MACHINE_GET_CLASS(machine); > + if (mc->get_hotplug_handler) { > + return mc->get_hotplug_handler(machine, dev); > + } > + } > + > + return NULL; > +} > + > HotplugHandler *qdev_get_hotplug_handler(DeviceState *dev) > { > - HotplugHandler *hotplug_ctrl = NULL; > + HotplugHandler *hotplug_ctrl; > > if (dev->parent_bus && dev->parent_bus->hotplug_handler) { > hotplug_ctrl = dev->parent_bus->hotplug_handler; > - } else if (object_dynamic_cast(qdev_get_machine(), TYPE_MACHINE)) { > - MachineState *machine = MACHINE(qdev_get_machine()); > - MachineClass *mc = MACHINE_GET_CLASS(machine); > - > - if (mc->get_hotplug_handler) { > - hotplug_ctrl = mc->get_hotplug_handler(machine, dev); > - } > + } else { > + hotplug_ctrl = qdev_get_machine_hotplug_handler(dev); > } > return hotplug_ctrl; > } qdev_get_machine_hotplug_handler() factored out of qdev_get_hotplug_handler(). Okay. Announcing it in the commit message could've saved me a few review brainwaves. > diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h > index 0a71bf8..51473ee 100644 > --- a/include/hw/qdev-core.h > +++ b/include/hw/qdev-core.h > @@ -286,6 +286,7 @@ DeviceState *qdev_try_create(BusState *bus, const char *name); > void qdev_init_nofail(DeviceState *dev); > void qdev_set_legacy_instance_id(DeviceState *dev, int alias_id, > int required_for_version); > +HotplugHandler *qdev_get_machine_hotplug_handler(DeviceState *dev); > HotplugHandler *qdev_get_hotplug_handler(DeviceState *dev); > void qdev_unplug(DeviceState *dev, Error **errp); > void qdev_simple_device_unplug_cb(HotplugHandler *hotplug_dev, > diff --git a/qdev-monitor.c b/qdev-monitor.c > index 9188d20..38c0fc2 100644 > --- a/qdev-monitor.c > +++ b/qdev-monitor.c > @@ -614,6 +614,11 @@ DeviceState *qdev_device_add(QemuOpts *opts, Error **errp) > if (qdev_hotplug && bus && !qbus_is_hotpluggable(bus)) { error_setg(errp, QERR_BUS_NO_HOTPLUG, bus->name); return NULL; } if (!migration_is_idle()) { error_setg(errp, "device_add not allowed while migrating"); return NULL; } /* create device */ dev = DEVICE(object_new(driver)); > if (bus) { > qdev_set_parent_bus(dev, bus); > + } else if (qdev_hotplug && !qdev_get_machine_hotplug_handler(dev)) { > + /* No bus, no machine hotplug handler --> device is not hotpluggable */ Long line. > + error_setg(&err, "Device '%s' can not be hotplugged on this machine", > + driver); > + goto err_del_dev; > } > > qdev_set_id(dev, qemu_opts_id(opts)); Hmm. We need to check "can hotplug" in two separate ways, with bus and without bus. Can we keep the two ways on one place? Something like if (qdev_hotplug) { if (bus && !qbus_is_hotpluggable(bus)) { error_setg(errp, QERR_BUS_NO_HOTPLUG, bus->name); return NULL; } if (!bus && !qdev_get_machine_hotplug_handler(dev)) { error_setg(&err, "Machine doesn't support hot-plugging device '%s'" driver); return NULL; } }