From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53379) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dzr6X-0000hS-Ta for qemu-devel@nongnu.org; Wed, 04 Oct 2017 17:21:23 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dzr6W-0002qX-Js for qemu-devel@nongnu.org; Wed, 04 Oct 2017 17:21:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45174) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dzr6W-0002pA-Br for qemu-devel@nongnu.org; Wed, 04 Oct 2017 17:21:20 -0400 Date: Wed, 4 Oct 2017 18:21:16 -0300 From: Eduardo Habkost Message-ID: <20171004212116.GD4015@localhost.localdomain> References: <1507049162-27026-1-git-send-email-thuth@redhat.com> <20171004133659.1f656303@nial.brq.redhat.com> <591132a9-c4e5-47cd-bab9-f017a116c2ae@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <591132a9-c4e5-47cd-bab9-f017a116c2ae@redhat.com> Subject: Re: [Qemu-devel] [PATCH] 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: Igor Mammedov , qemu-devel@nongnu.org, Paolo Bonzini , Markus Armbruster , "Dr. David Alan Gilbert" , Peter Maydell On Wed, Oct 04, 2017 at 09:29:54PM +0200, Thomas Huth wrote: > On 04.10.2017 13:36, Igor Mammedov wrote: > > On Tue, 3 Oct 2017 18:46:02 +0200 > > Thomas Huth wrote: > > > >> 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). So devices clearly need a hotplug > >> controller when they are suitable for device_add. > >> The code in qdev_device_add() already checks whether the bus has a proper > >> hotplug controller, but for devices that do not have a corresponding bus, > >> there is no appropriate check available. 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. > >> > >> Signed-off-by: Thomas Huth > >> --- > >> This is the follow-up patch from my earlier try "hw/core/qdev: Do not > >> allow hot-plugging without hotplug controller" ... AFAICS the function > >> qdev_device_add() is now the right spot to do the check. > >> > >> hw/core/qdev.c | 28 ++++++++++++++++++++-------- > >> include/hw/qdev-core.h | 1 + > >> qdev-monitor.c | 9 +++++++++ > >> 3 files changed, 30 insertions(+), 8 deletions(-) > >> > >> diff --git a/hw/core/qdev.c b/hw/core/qdev.c > >> index 606ab53..a953ec9 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; > >> } > >> diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h > >> index 0891461..5aa536d 100644 > >> --- a/include/hw/qdev-core.h > >> +++ b/include/hw/qdev-core.h > >> @@ -285,6 +285,7 @@ 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 8fd6df9..2891dde 100644 > >> --- a/qdev-monitor.c > >> +++ b/qdev-monitor.c > >> @@ -626,6 +626,15 @@ DeviceState *qdev_device_add(QemuOpts *opts, Error **errp) > >> return NULL; > >> } > >> > >> + /* In case we don't have a bus, there must be a machine hotplug handler */ > >> + if (qdev_hotplug && !bus && !qdev_get_machine_hotplug_handler(dev)) { > > current machine hotplug handler serves both cold and hot-plug so in reality it's > > just 'plug' handler. > > > > Is there a point -device/device_add devices on board that doesn't have 'hotplug' > > handler that would wire device up properly? > > Sorry, I did not get that question ... do you mean whether there's any > code that uses qdev_device_add() to add a device without hotplug > controller? I don't think so. It's currently only used by > qmp_device_add() for the QMP/HMP command, in vl.c for -device and in the > USB code for xen-usb host device. So this function currently really only > makes sense for devices that have a hotplug controller. I assume you are talking only about hotpluggable devices. With -device, qdev_device_add() is also used for devices that don't have a hotplug controller, but this is supposed to be true only for non-hotpluggable devices. -- Eduardo