Re: [Qemu-devel] [PATCH v4 5/9] hw/timer: QOM'ify m48txx_sysbus (pass 2)

[xiaoqiang zhao]

>> 在 2016年2月22日，19:03，Peter Maydell <address@hidden> 写道：
>> 
>>> On 22 February 2016 at 10:28, hitmoon <address@hidden> wrote:
>>> 在 2016年02月22日 17:24, Peter Maydell 写道:
>>> Just noticed this won't work as it is -- the vmstate
>>> struct is for the M48t59State*, but the ISA and
>>> Sysbus wrappers have their own structs which are
>>> what the dc->vmsd will be wanting to operate on.
>>> You'd need extra VMState structs I think and
>>> somebody who knows migration better than me to say
>>> whether that is a migration compat break.
> 
>> It seems that the old code also use the same vmstate structure. Maybe it's a
>> common structure which will not be used at the same time.
> 
> The old code passes vmstate_register() a pointer to the
> M48t59State, and so the offsets in the vmstate line up correctly
> with the fields it wants to access. If you use dc->vmsd then the
> pointer that is (implicitly) used is the pointer to the device
> structure itself, which is not the same address as the
> M48t59State embedded inside that struct.
> 
> You'd basically need to have extra VMState structures for the
> devices themselves which just said "inside this M48txxISAState
> is an M48t59State", and "inside this M48txxSysBusState is a
> M48t59State" and referred to the existing vmstate for the
> M48t59State.
> 
> thanks
> -- PMM

I will have a closer look.