Re: [PATCH v5 4/8] vt82c686: Introduce abstract TYPE_VIA_ISA and base vt82c686b_isa on it

[Philippe Mathieu-Daudé]

+Gerd

On 3/9/21 5:00 PM, Dr. David Alan Gilbert wrote:
> * David Gibson (david@gibson.dropbear.id.au) wrote:
>> On Thu, Mar 04, 2021 at 11:42:10PM +0100, Philippe Mathieu-Daudé wrote:
>>> On 3/4/21 9:16 PM, BALATON Zoltan wrote:
>>>> On Thu, 4 Mar 2021, Philippe Mathieu-Daudé wrote:
>>>>> On 3/2/21 10:11 PM, BALATON Zoltan wrote:
>>>>>> To allow reusing ISA bridge emulation for vt8231_isa move the device
>>>>>> state of vt82c686b_isa emulation in an abstract via_isa class.
>>>>>>
>>>>>> Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
>>>>>> ---
>>>>>>  hw/isa/vt82c686.c        | 70 ++++++++++++++++++++++------------------
>>>>>>  include/hw/pci/pci_ids.h |  2 +-
>>>>>>  2 files changed, 40 insertions(+), 32 deletions(-)
>>>>>>
>>>>>> diff --git a/hw/isa/vt82c686.c b/hw/isa/vt82c686.c
>>>>>> index 72234bc4d1..5137f97f37 100644
>>>>>> --- a/hw/isa/vt82c686.c
>>>>>> +++ b/hw/isa/vt82c686.c
>>>>>> @@ -609,24 +609,48 @@ static const TypeInfo vt8231_superio_info = {
>>>>>>  };
>>>>>>
>>>>>>
>>>>>> -OBJECT_DECLARE_SIMPLE_TYPE(VT82C686BISAState, VT82C686B_ISA)
>>>>>> +#define TYPE_VIA_ISA "via-isa"
>>>>>> +OBJECT_DECLARE_SIMPLE_TYPE(ViaISAState, VIA_ISA)
>>>>>>
>>>>>> -struct VT82C686BISAState {
>>>>>> +struct ViaISAState {
>>>>>>      PCIDevice dev;
>>>>>>      qemu_irq cpu_intr;
>>>>>>      ViaSuperIOState *via_sio;
>>>>>>  };
>>>>>>
>>>>>> +static const VMStateDescription vmstate_via = {
>>>>>> +    .name = "via-isa",
>>>>>
>>>>> You changed the migration stream name, so I think we have
>>>>> a problem with migration... No clue how to do that properly.
>>>>
>>>> I don't think these machines support migration or state description of
>>>> vt86c686b was not missing something before these patches that would make
>>>> it not work anyway so I did not worry about this too much. I doubt
>>>> anybody wants to migrate a fuloong2e machine so this should not be a
>>>> problem in practice but maybe you can mention it in the release notes if
>>>> you think that would be necessary.
>>>
>>> Maybe just add in the description:
>>>
>>>  This change breaks migration back compatibility, but
>>>  this is not an issue for the Fuloong2E machine.
>>
>> Hrm.  If migration was never supported, why is there a vmstate
>> description there at all though?
>>
>> That said, I don't think breaking compat is a problem: that's only an
>> issue where we actually have versioned machine types, which covers
>> only pc, pseries, arm virt and a very few others.  I don't think this
>> device was used on any of them.
> 
> Except 'vt82c686b-usb-uhci' is a generic PCI device that anyone can
> instantiate, so it's not actually Fuloong specific.

I tend to see this as a bug, as this is a function specific to the
southbridge chipset and isn't meant to be used apart...

If this isn't a feature but really a bug, a simple way to clean this
is to make struct UHCIInfo and usb_uhci_common_realize() public, and
type_register "vt82c686b-usb-uhci" elsewhere.

Gerd would that work with you?