Previously it was allowed to call object_unparent() for a memory region in instance_finalize() of its parent. However, such a call typically has no effect because child objects get unparented before instance_finalize().
Worse, memory regions typically gets finalized when they get unparented before instance_finalize(). This means calling object_unparent() for them in instance_finalize() is to call the function for an object already finalized, which should be avoided. Signed-off-by: Akihiko Odaki <akihiko.od...@daynix.com> --- docs/devel/memory.rst | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/docs/devel/memory.rst b/docs/devel/memory.rst index 69c5e3f914ac..83760279e3db 100644 --- a/docs/devel/memory.rst +++ b/docs/devel/memory.rst @@ -168,11 +168,10 @@ and VFIOQuirk in hw/vfio/pci.c. You must not destroy a memory region as long as it may be in use by a device or CPU. In order to do this, as a general rule do not create or -destroy memory regions dynamically during a device's lifetime, and only -call object_unparent() in the memory region owner's instance_finalize -callback. The dynamically allocated data structure that contains the -memory region then should obviously be freed in the instance_finalize -callback as well. +destroy memory regions dynamically during a device's lifetime, and do not +call object_unparent(). The dynamically allocated data structure that contains +the memory region then should be freed in the instance_finalize callback, which +is called after it gets unparented. If you break this rule, the following situation can happen: @@ -199,8 +198,9 @@ but nevertheless it is used in a few places. For regions that "have no owner" (NULL is passed at creation time), the machine object is actually used as the owner. Since instance_finalize is -never called for the machine object, you must never call object_unparent -on regions that have no owner, unless they are aliases or containers. +never called for the machine object, you must never free regions that have no +owner, unless they are aliases or containers, which you can manually call +object_unparent() for. Overlapping regions and priority --- base-commit: 31669121a01a14732f57c49400bc239cf9fd505f change-id: 20240829-memory-cfd3ee0af44d Best regards, -- Akihiko Odaki <akihiko.od...@daynix.com>
