[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH for-2.10 3/3] qdev: defer DEVICE_DEL event until
From: |
Greg Kurz |
Subject: |
Re: [Qemu-devel] [PATCH for-2.10 3/3] qdev: defer DEVICE_DEL event until instance_finalize() |
Date: |
Mon, 31 Jul 2017 19:11:19 +0200 |
On Wed, 26 Jul 2017 20:30:55 -0500
Michael Roth <address@hidden> 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 <address@hidden>
> ---
Reviewed-by: Greg Kurz <address@hidden>
> 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;
> - }
> }
>
> static void device_class_init(ObjectClass *class, void *data)
pgpv92yhaCkdM.pgp
Description: OpenPGP digital signature