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Date: Tue, 1 Mar 2011 13:53:46 +0000
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From: Peter Maydell <peter.maydell@linaro.org>
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Subject: [Qemu-devel] Re: [PATCH 1/2] hw/arm_sysctl.c: Add the Versatile
	Express system registers
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To: quintela@redhat.com
Cc: patches@linaro.org, Bahadir Balban <bbalban@b-labs.com>, qemu-devel@nongnu.org, Amit Mahajan <amit.mahajan@b-labs.com>, =?UTF-8?B?RGF3aWQgQ2nEmcW8YXJraWV3aWN6?= <dawidc@b-labs.com>

2011/3/1 Juan Quintela <quintela@redhat.com>:
> Peter Maydell <peter.maydell@linaro.org> wrote:
>
> Hi
>
>> @@ -41,6 +44,9 @@ static const VMStateDescription vmstate_arm_sysctl =3D=
 {
>> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0VMSTATE_UINT32(flags, arm_sysctl_state=
),
>> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0VMSTATE_UINT32(nvflags, arm_sysctl_sta=
te),
>> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0VMSTATE_UINT32(resetlevel, arm_sysctl_=
state),
>> + =C2=A0 =C2=A0 =C2=A0 =C2=A0VMSTATE_UINT32(sys_cfgdata, arm_sysctl_stat=
e),
>> + =C2=A0 =C2=A0 =C2=A0 =C2=A0VMSTATE_UINT32(sys_cfgctrl, arm_sysctl_stat=
e),
>> + =C2=A0 =C2=A0 =C2=A0 =C2=A0VMSTATE_UINT32(sys_cfgstat, arm_sysctl_stat=
e),
>> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0VMSTATE_END_OF_LIST()
>> =C2=A0 =C2=A0 =C2=A0}
>> =C2=A0};
>
> Three options (about migration):
> - left things as they are and become incompatible without changing versio=
ns
> - if you don't care about backward compatibility, just add +1 to all the
> =C2=A0version fields and you are done.
> - add this fields only for the new version.
>
> IMHO 1st one is the worse option. =C2=A0I will go with the middle one (as=
 far
> as I know, nobody on arm uses interversion migration (as far as I know,
> nobody uses migration at all).

OK, so in:
static const VMStateDescription vmstate_arm_sysctl =3D {
    .name =3D "realview_sysctl",
    .version_id =3D 1,
    .minimum_version_id =3D 1,

I just bump the '1' in both cases to '2' ?

I've only ever used the save/restore for debugging purposes.
We know for certain that nobody can have been doing migration
with versatile platforms before this year, because we only
added save/load support to arm_sysctl.c in December 2010 :-)

(What's the equivalent version-bump that needs to be done
when entries are added to target-arm/machine.c's save and
restore code?)

thanks
-- PMM