On 11/30/2016 05:06 PM, Michael Roth wrote: > 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.
Nice analysis. > > 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 checks in {qmp,hmp}_object_del 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. Phew. Yeah, libvirt avoiding HMP where possible saves a lot of hassles. > +++ b/hmp.c > @@ -2072,6 +2072,16 @@ void hmp_object_del(Monitor *mon, const QDict *qdict) > > user_creatable_del(id, &err); > hmp_handle_error(mon, &err); > + > + /* if object was defined on the command-line, remove its corresponding > + * option group entry > + */ > + if (err == NULL) { > + QemuOptsList *opt_group = qemu_find_opts_err("object", &err); > + if (opt_group) { > + qemu_opts_del(qemu_opts_find(opt_group, id)); > + } > + } This one looks okay. > } > > void hmp_info_memdev(Monitor *mon, const QDict *qdict) > diff --git a/qmp.c b/qmp.c > index 0028f0b..87c545d 100644 > --- a/qmp.c > +++ b/qmp.c > @@ -686,6 +686,16 @@ void qmp_object_add(const char *type, const char *id, > void qmp_object_del(const char *id, Error **errp) > { > user_creatable_del(id, errp); > + > + /* if object was defined on the command-line, remove its corresponding > + * option group entry > + */ > + if (!(errp && *errp)) { But this is wrong. Please spin a v2 that uses a local Error object, then use error_propagate(err, errp). Making anything conditional on whether an error occurred requires a local object, since the caller can pass in NULL, but you want your cleanup to happen even when the caller doesn't care about errors. > + QemuOptsList *opt_group = qemu_find_opts_err("object", errp); > + if (opt_group) { > + qemu_opts_del(qemu_opts_find(opt_group, id)); > + } > + } > } > > MemoryDeviceInfoList *qmp_query_memory_devices(Error **errp) > -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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