Re: [PATCH 05/11] qdev: Make DeviceState.id independent of QemuOpts

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

24.09.2021 18:10, Kevin Wolf wrote:
> Am 24.09.2021 um 16:02 hat Vladimir Sementsov-Ogievskiy geschrieben:
>> 24.09.2021 12:04, Kevin Wolf wrote:
>>> DeviceState.id is a pointer to a string that is stored in the QemuOpts
>>> object DeviceState.opts and freed together with it. We want to create
>>> devices without going through QemuOpts in the future, so make this a
>>> separately allocated string.
>>>
>>> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
>>
>> Interesting that in hw/xen/xen-legacy-backend.c
>> g_strdup_printf-allocated id is passed to qdev_set_id prior this
>> patch. So, the patch seems to fix that small leak. Worth to mention?
> 
> Ok, I can mention it explicitly.
> 
>>> ---
>>>    include/hw/qdev-core.h              | 2 +-
>>>    include/monitor/qdev.h              | 2 +-
>>>    hw/arm/virt.c                       | 2 +-
>>>    hw/core/qdev.c                      | 1 +
>>>    hw/pci-bridge/pci_expander_bridge.c | 2 +-
>>>    hw/ppc/e500.c                       | 2 +-
>>>    softmmu/qdev-monitor.c              | 5 +++--
>>>    7 files changed, 9 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
>>> index 34c8a7506a..1857d9698e 100644
>>> --- a/include/hw/qdev-core.h
>>> +++ b/include/hw/qdev-core.h
>>> @@ -176,7 +176,7 @@ struct DeviceState {
>>>        Object parent_obj;
>>>        /*< public >*/
>>> -    const char *id;
>>> +    char *id;
>>>        char *canonical_path;
>>>        bool realized;
>>>        bool pending_deleted_event;
>>> diff --git a/include/monitor/qdev.h b/include/monitor/qdev.h
>>> index eaa947d73a..389287eb44 100644
>>> --- a/include/monitor/qdev.h
>>> +++ b/include/monitor/qdev.h
>>> @@ -9,6 +9,6 @@ void qmp_device_add(QDict *qdict, QObject **ret_data, Error **errp);
>>>    int qdev_device_help(QemuOpts *opts);
>>>    DeviceState *qdev_device_add(QemuOpts *opts, Error **errp);
>>> -void qdev_set_id(DeviceState *dev, const char *id);
>>> +void qdev_set_id(DeviceState *dev, char *id);
>>>    #endif
>>> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
>>> index 1d59f0e59f..f933d48d3b 100644
>>> --- a/hw/arm/virt.c
>>> +++ b/hw/arm/virt.c
>>> @@ -1459,7 +1459,7 @@ static void create_platform_bus(VirtMachineState *vms)
>>>        MemoryRegion *sysmem = get_system_memory();
>>>        dev = qdev_new(TYPE_PLATFORM_BUS_DEVICE);
>>> -    dev->id = TYPE_PLATFORM_BUS_DEVICE;
>>> +    dev->id = g_strdup(TYPE_PLATFORM_BUS_DEVICE);
>>>        qdev_prop_set_uint32(dev, "num_irqs", PLATFORM_BUS_NUM_IRQS);
>>>        qdev_prop_set_uint32(dev, "mmio_size", vms->memmap[VIRT_PLATFORM_BUS].size);
>>>        sysbus_realize_and_unref(SYS_BUS_DEVICE(dev), &error_fatal);
>>> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
>>> index cefc5eaa0a..d918b50a1d 100644
>>> --- a/hw/core/qdev.c
>>> +++ b/hw/core/qdev.c
>>> @@ -956,6 +956,7 @@ static void device_finalize(Object *obj)
>>>        }
>>>        qemu_opts_del(dev->opts);
>>> +    g_free(dev->id);
>>>    }
>>>    static void device_class_base_init(ObjectClass *class, void *data)
>>> diff --git a/hw/pci-bridge/pci_expander_bridge.c b/hw/pci-bridge/pci_expander_bridge.c
>>> index 7112dc3062..10e6e7c2ab 100644
>>> --- a/hw/pci-bridge/pci_expander_bridge.c
>>> +++ b/hw/pci-bridge/pci_expander_bridge.c
>>> @@ -245,7 +245,7 @@ static void pxb_dev_realize_common(PCIDevice *dev, bool pcie, Error **errp)
>>>        } else {
>>>            bus = pci_root_bus_new(ds, "pxb-internal", NULL, NULL, 0, TYPE_PXB_BUS);
>>>            bds = qdev_new("pci-bridge");
>>> -        bds->id = dev_name;
>>> +        bds->id = g_strdup(dev_name);
>>>            qdev_prop_set_uint8(bds, PCI_BRIDGE_DEV_PROP_CHASSIS_NR, pxb->bus_nr);
>>>            qdev_prop_set_bit(bds, PCI_BRIDGE_DEV_PROP_SHPC, false);
>>>        }
>>> diff --git a/hw/ppc/e500.c b/hw/ppc/e500.c
>>> index 95451414dd..960e7efcd3 100644
>>> --- a/hw/ppc/e500.c
>>> +++ b/hw/ppc/e500.c
>>> @@ -1006,7 +1006,7 @@ void ppce500_init(MachineState *machine)
>>>        /* Platform Bus Device */
>>>        if (pmc->has_platform_bus) {
>>>            dev = qdev_new(TYPE_PLATFORM_BUS_DEVICE);
>>> -        dev->id = TYPE_PLATFORM_BUS_DEVICE;
>>> +        dev->id = g_strdup(TYPE_PLATFORM_BUS_DEVICE);
>>>            qdev_prop_set_uint32(dev, "num_irqs", pmc->platform_bus_num_irqs);
>>>            qdev_prop_set_uint32(dev, "mmio_size", pmc->platform_bus_size);
>>>            sysbus_realize_and_unref(SYS_BUS_DEVICE(dev), &error_fatal);
>>> diff --git a/softmmu/qdev-monitor.c b/softmmu/qdev-monitor.c
>>> index 034b999401..1207e57a46 100644
>>> --- a/softmmu/qdev-monitor.c
>>> +++ b/softmmu/qdev-monitor.c
>>> @@ -592,7 +592,8 @@ static BusState *qbus_find(const char *path, Error **errp)
>>>        return bus;
>>>    }
>>> -void qdev_set_id(DeviceState *dev, const char *id)
>>> +/* Takes ownership of @id, will be freed when deleting the device */
>>> +void qdev_set_id(DeviceState *dev, char *id)
>>>    {
>>>        if (id) {
>>>            dev->id = id;
>>> @@ -690,7 +691,7 @@ DeviceState *qdev_device_add(QemuOpts *opts, Error **errp)
>>>            }
>>>        }
>>> -    qdev_set_id(dev, qemu_opts_id(opts));
>>> +    qdev_set_id(dev, g_strdup(qemu_opts_id(opts)));
>>>        /* set properties */
>>>        if (qemu_opt_foreach(opts, set_property, dev, errp)) {
>>>
>>
>> In hw/pci/pci_bridge.c
>>
>> we do
>>
>>     br->bus_name = dev->qdev.id
>>
>> It seems bad, as we now stole dynamic pointer, that may be freed later.
> 
> If it's bad now, it was as bad before because previously it was just a
> pointer stolen from the QemuOpts that is freed in the same function as
> dev->id after this patch.
> 

Ah, right, OK.

> I think the code is correct (it's just another field of the same device,
> the real bus name is just a copy of it, and the bus can't outlive the
> device that owns it anyway), but it might be bad style.
> 


Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>


-- 
Best regards,
Vladimir