Children are automatically unparented so manually unparenting is
unnecessary.
Worse, automatic unparenting happens before the instance_finalize()
callback of the parent gets called, so object_unparent() calls in
the callback will refer to objects that are already unparented, which
is semantically incorrect.
Remove the instruction to call object_unparent(), and the exception
of the "do not call object_unparent()" rule for instance_finalize().
Signed-off-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Link: https://lore.kernel.org/r/20250924-use-v4-1-07c6c598f53d@rsg.ci.i.u-tokyo.ac.jp
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Currently, QEMU refcounts the MR by always taking it from the owner.
It's common that one object will have multiple MR objects embeded in the
object itself. All the MRs in this case share the same lifespan of the
owner object.
It's also common that in the instance_init() of an object, MR A can be a
container of MR B, C, D, by using memory_region_add_subregion*() set of
memory region APIs.
Now we have a circular reference issue, as when adding subregions for MR A,
we essentially incremented the owner's refcount within the instance_init(),
meaning the object will be self-boosted and its refcount can never go down
to zero if the MRs won't get detached properly before object's finalize().
Delete subregions within object's finalize() won't work either, because
finalize() will be invoked only if the refcount goes to zero first. What
is worse, object_finalize() will do object_property_del_all() first before
object_deinit(). Since embeded MRs will be properties of the owner object,
it means they'll be freed _before_ the owner's finalize().
To fix that, teach memory API to stop refcount on MRs that share the same
owner. Because if they share the lifecycle of the owner, then they share
the same lifecycle between themselves, hence the refcount doesn't help but
only introduce troubles.
Meanwhile, allow auto-detachments of MRs during finalize() of MRs even
against its container, as long as they belong to the same owner.
The latter is needed because now it's possible to have MRs' finalize()
happen in any order when they share the same lifespan with a same owner.
In this case, we should allow finalize() to happen in any order of either
the parent or child MR. Loose the mr->container check in MR's finalize()
to allow auto-detach. Double check it shares the same owner.
Proper document this behavior in code.
This patch is heavily based on the work done by Akihiko Odaki:
https://lore.kernel.org/r/CAFEAcA8DV40fGsci76r4yeP1P-SP_QjNRDD2OzPxjx5wRs0GEg@mail.gmail.com
Cc: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Clément Mathieu--Drif <clement.mathieu--drif@eviden.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Tested-by: Peter Maydell <peter.maydell@linaro.org>
Link: https://lore.kernel.org/r/20250826221750.285242-1-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Convert the existing includes with
sed -i ,exec/memory.h,system/memory.h,g
Move the include within cpu-all.h into a !CONFIG_USER_ONLY block.
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
We do mention the limitation of single parenthood for
memory_region_add_subregion but lets also make it clear how aliases
help solve that conundrum.
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20220110175104.2908956-7-alex.bennee@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Convert the memory API documentation from plain text
to restructured text format.
This is a very minimal conversion: all I had to change
was to mark up the ASCII art parts as Sphinx expects
for 'literal blocks', and fix up the bulleted lists
(Sphinx expects no leading space before the bullet, and
wants a blank line before after any list).
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Acked-by: Aleksandar Markovic <amarkovic@wavecomp.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Cleber Rosa <crosa@redhat.com>
Message-id: 20190305172139.32662-3-peter.maydell@linaro.org
Message-id: 20190228145624.24885-3-peter.maydell@linaro.org
