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From: hitmoon <zxq_yx_007@163.com>
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Date: Tue, 23 Feb 2016 13:11:56 +0800
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Subject: Re: [Qemu-devel] [PATCH v4 5/9] hw/timer: QOM'ify m48txx_sysbus
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: Igor Mitsyanko <i.mitsyanko@gmail.com>, Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>, QEMU Developers <qemu-devel@nongnu.org>, Michael Walle <michael@walle.cc>, qemu-arm <qemu-arm@nongnu.org>, "Edgar E. Iglesias" <edgar.iglesias@gmail.com>, Guan Xuetao <gxt@mprc.pku.edu.cn>, =?UTF-8?Q?Andreas_F=c3=a4rber?= <afaerber@suse.de>


在 2016年02月22日 19:03, Peter Maydell 写道:
> On 22 February 2016 at 10:28, hitmoon <zxq_yx_007@163.com> 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 add a new  structure for m48t59_isa as follows:

static const VMStateDescription vmstate_m48t59_isa = {
     .name = "m48t59-isa",
     .version_id = 1,
     .minimum_version_id = 1,
     .fields = (VMStateField[]) {
         VMSTATE_UINT8(state.lock, M48txxISAState),
         VMSTATE_UINT16(state.addr, M48txxISAState),
         VMSTATE_VBUFFER_UINT32(state.buffer, M48txxISAState, 0, NULL, 
0, state.size),
         VMSTATE_END_OF_LIST()
     }
};

is this correct?