Quoting Auger Eric (2017-08-09 09:04:54)
> 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);
Hi Eric,
Sorry for missing your reply previously. That comment does indeed need
some adjusting after patch 3. Will fix it up for v2.
>
> Thanks
>
> Eric
> > }
> >
> > static void device_class_init(ObjectClass *class, void *data)
> >
>
