Hi Michael, On 27/07/2017 03:30, Michael Roth wrote: > DEVICE_DEL is currently emitted when a Device is unparented, as > opposed to when it is finalized. The main design motivation for this > seems to be that after unparent()/unrealize(), the Device is no > longer visible to the guest, and thus the operation is complete > from the perspective of management. > > However, there are cases where remaining host-side cleanup is also > pertinent to management. The is generally handled by treating these > resources as aspects of the "backend", which can be managed via > separate interfaces/events, such as blockdev_add/del, netdev_add/del, > object_add/del, etc, but some devices do not have this level of > compartmentalization, namely vfio-pci, and possibly to lend themselves > well to it. > > In the case of vfio-pci, the "backend" cleanup happens as part of > the finalization of the vfio-pci device itself, in particular the > cleanup of the VFIO group FD. Failing to wait for this cleanup can > result in tools like libvirt attempting to rebind the device to > the host while it's still being used by VFIO, which can result in > host crashes or other misbehavior depending on the host driver. > > Deferring DEVICE_DEL still affords us the ability to manage backends > explicitly, while also addressing cases like vfio-pci's, so we > implement that approach here. > > An alternative proposal involving having VFIO emit a separate event > to denote completion of host-side cleanup was discussed, but the > prevailing opinion seems to be that it is not worth the added > complexity, and leaves the issue open for other Device implementations > solve in the future. > > Signed-off-by: Michael Roth <mdr...@linux.vnet.ibm.com> > --- > hw/core/qdev.c | 23 ++++++++++++----------- > 1 file changed, 12 insertions(+), 11 deletions(-) > > diff --git a/hw/core/qdev.c b/hw/core/qdev.c > index 08c4061..d14acba 100644 > --- a/hw/core/qdev.c > +++ b/hw/core/qdev.c > @@ -1067,7 +1067,6 @@ static void device_finalize(Object *obj) > NamedGPIOList *ngl, *next; > > DeviceState *dev = DEVICE(obj); > - qemu_opts_del(dev->opts); > > QLIST_FOREACH_SAFE(ngl, &dev->gpios, node, next) { > QLIST_REMOVE(ngl, node); > @@ -1078,6 +1077,18 @@ static void device_finalize(Object *obj) > * here > */ > } > + > + /* Only send event if the device had been completely realized */ > + if (dev->pending_deleted_event) { > + g_assert(dev->canonical_path); > + > + qapi_event_send_device_deleted(!!dev->id, dev->id, > dev->canonical_path, > + &error_abort); > + g_free(dev->canonical_path); > + dev->canonical_path = NULL; > + } > + > + qemu_opts_del(dev->opts); > } > > static void device_class_base_init(ObjectClass *class, void *data) > @@ -1107,16 +1118,6 @@ static void device_unparent(Object *obj) > object_unref(OBJECT(dev->parent_bus)); > dev->parent_bus = NULL; > } > - > - /* Only send event if the device had been completely realized */ > - if (dev->pending_deleted_event) { > - g_assert(dev->canonical_path); > - > - qapi_event_send_device_deleted(!!dev->id, dev->id, > dev->canonical_path, > - &error_abort); > - g_free(dev->canonical_path); > - dev->canonical_path = NULL; > - } is the code below, introduced in patch 1/device_set_realized() still relevant? /* always re-initialize since we clean up in device_unparent() instead * of unrealize() */ g_free(dev->canonical_path);
Thanks Eric > } > > static void device_class_init(ObjectClass *class, void *data) >