Re: [RFC 1/4] memory: add memory_region_init_io_with_dev interface

[Jason Wang <jasowang@redhat.com>]

On 2020/9/10 下午10:37, Li Qiang wrote:
> Alexander Bulekov <alxndr@bu.edu> 于2020年9月9日周三 下午10:28写道：
>> On 200909 1258, Li Qiang wrote:
>>> Gerd Hoffmann <kraxel@redhat.com> 于2020年9月9日周三 下午12:49写道：
>>>> On Wed, Sep 09, 2020 at 10:15:47AM +0800, Jason Wang wrote:
>>>>> On 2020/9/9 上午12:41, Li Qiang wrote:
>>>>>> Currently the MR is not explicitly connecting with its device instead of
>>>>>> a opaque. In most situation this opaque is the deivce but it is not an
>>>>>> enforcement. This patch adds a DeviceState member of to MemoryRegion
>>>>>> we will use it in later patch.
>>>>>
>>>>> I don't have a deep investigation. But I wonder whether we could make sure
>>>>> of owner instead of adding a new field here.
>>>> Should be possible.  There is object_dynamic_cast() which can be used to
>>>> figure whenever a given owner object is a device.
>>>>
>>> I found most caller of 'memory_region_init_io' will set the owner to
>>> the device object.
>>> But some of them will just set it to NULL. Do will have a clear rule
>>> that the device's MR
>>> 'owner' should be the device object? If yes, we can use this field.
>>>
>> Those seem to be devices that havent't been QOM-imfied yet?  Maybe those
>> devices are unlikely to be affected by these issues, though...
>>
> No it seems not related QOM-ified.
>
>> For i386, it seems like parallel, port80, portF0, pckbd, and xen_pvdevice .. ?
>> I'm guessing none of these do DMA.
>>
> In fact xen_pvdevice is MMIO but the handlers does nothing.
>
> There are some other example than i386 such as the riscv in
> hw/riscv/sifive_uart.c
>
> If we have a rule to force the 'MR's owner to the device then we can
> fix these NULL owner MR.
>
> Thanks,
> Li Qiang


I guess maybe we can start from the ones whose owner is a device and 
convert the rest on top (if necessary)?

Thanks


>
>> +CC Stefan, since he replied to the other thread.
>>
>>> Thanks,
>>> Li Qiang
>>>
>>>> take care,
>>>>    Gerd
>>>>