Michael Roth <mdr...@linux.vnet.ibm.com> writes:
> Currently objects specified on the command-line are only partially
> cleaned up when 'object_del' is issued in either HMP or QMP: the
> object itself is fully finalized, but the QemuOpts are not removed.
> This results in the following behavior:
>
> x86_64-softmmu/qemu-system-x86_64 -monitor stdio \
> -object memory-backend-ram,id=ram1,size=256M
>
> QEMU 2.7.91 monitor - type 'help' for more information
> (qemu) object_del ram1
> (qemu) object_del ram1
> object 'ram1' not found
> (qemu) object_add memory-backend-ram,id=ram1,size=256M
> Duplicate ID 'ram1' for object
> Try "help object_add" for more information
>
> which can be an issue for use-cases like memory hotplug.
>
> This happens on the HMP side because hmp_object_add() attempts to
> create a temporary QemuOpts entry with ID 'ram1', which ends up
> conflicting with the command-line-created entry, since it was never
> cleaned up during the previous hmp_object_del() call.
>
> We address this by adding a check in user_creatable_del(), which
> is called by both qmp_object_del() and hmp_object_del() to handle
> the actual object cleanup, to determine whether an option group entry
> matching the object's ID is present and removing it if it is.
>
> Note that qmp_object_add() never attempts to create a temporary
> QemuOpts entry, so it does not encounter the duplicate ID error,
> which is why this isn't generally visible in libvirt.
>
> Cc: "Dr. David Alan Gilbert" <dgilb...@redhat.com>
> Cc: Markus Armbruster <arm...@redhat.com>
> Cc: Eric Blake <ebl...@redhat.com>
> Cc: Daniel Berrange <berra...@redhat.com>
> Cc: qemu-sta...@nongnu.org
> Signed-off-by: Michael Roth <mdr...@linux.vnet.ibm.com>
> Reviewed-by: Daniel P. Berrange <berra...@redhat.com>
> ---
> qom/object_interfaces.c | 7 +++++++
> tests/check-qom-proplist.c | 4 ++--
> 2 files changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/qom/object_interfaces.c b/qom/object_interfaces.c
> index ded4d84..b462a74 100644
> --- a/qom/object_interfaces.c
> +++ b/qom/object_interfaces.c
> @@ -5,6 +5,7 @@
> #include "qapi-visit.h"
> #include "qapi/qobject-output-visitor.h"
> #include "qapi/opts-visitor.h"
> +#include "qemu/config-file.h"
>
> void user_creatable_complete(Object *obj, Error **errp)
> {
> @@ -209,6 +210,12 @@ void user_creatable_del(const char *id, Error **errp)
> error_setg(errp, "object '%s' is in use, can not be deleted", id);
> return;
> }
> +
> + /* if object was defined on the command-line, remove its corresponding
> + * option group entry
> + */
Consider adding wings to both ends of multi-line comments.
> + qemu_opts_del(qemu_opts_find(qemu_find_opts_err("object", NULL), id));
qemu_find_opts_err() can't fail. If it did, qemu_opts_find() would
crash. Okay.
Elsewhere, we use qemu_opts_find(qemu_find_opts(NAME)), which would
report an error to stderr / monitor before crashing. Also okay.
Perhaps the cleanest (but not the tersest) way to skin this cat:
qemu_opts_find(qemu_find_opts_err(&error_abort)).
Your choice.
> +
> object_unparent(obj);
> }
>
> diff --git a/tests/check-qom-proplist.c b/tests/check-qom-proplist.c
> index e3f56ca..c5d4b60 100644
> --- a/tests/check-qom-proplist.c
> +++ b/tests/check-qom-proplist.c
> @@ -437,9 +437,9 @@ static void test_dummy_createcmdl(void)
> * check for this in user_creatable_del() and remove the QemuOpts if
> * it is present.
> *
> - * FIXME: add an assert to verify that the QemuOpts is cleaned up
> - * once the corresponding cleanup code is added.
> + * The below check ensures this works as expected.
> */
> + g_assert(qemu_opts_find(&qemu_object_opts, "dev0") == NULL);
There's also g_assert_null(), which could result in a more helpful
message when the assertion fails. Your choice.
> }
>
> static void test_dummy_badenum(void)
