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From: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <2f665608-cf35-2774-ddf7-05efacd55e5e@redhat.com>
Date: Mon, 4 Mar 2019 11:50:18 +0100
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Subject: Re: [Qemu-devel] [PATCH] lsi: implement basic SBCL functionality
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: Sven Schnelle <svens@stackframe.org>, QEMU Developers <qemu-devel@nongnu.org>, Fam Zheng <fam@euphon.net>

On 04/03/19 11:19, Peter Maydell wrote:
> On Fri, 15 Feb 2019 at 09:38, Paolo Bonzini <pbonzini@redhat.com> wrote=
:
>>
>> On 14/02/19 23:04, Sven Schnelle wrote:
>>> @@ -2202,6 +2224,7 @@ static const VMStateDescription vmstate_lsi_scs=
i =3D {
>>>          VMSTATE_UINT8(stime0, LSIState),
>>>          VMSTATE_UINT8(respid0, LSIState),
>>>          VMSTATE_UINT8(respid1, LSIState),
>>> +        VMSTATE_UINT8(sbcl, LSIState),
>>
>> This breaks live migration.  You need to bump the version number highe=
r
>> in vmstate_lsi_scsi and use "VMSTATE_UINT8_V(sbcl, LSIState, 1)" so th=
at
>> the field is only marshalled/unmarshalled for version 1 of the migrati=
on
>> state.
>=20
> I thought we preferred to do this with migration subsections
> rather than versioning fields these days ? In this case I
> think a subsection that says "needed if sbcl is non-zero" would
> do the right thing.

Yes, we prefer migration subsections but the only advantage is support
for backwards migration.  LSI is not a device for which I would
guarantee that backwards migration works at all, and it is not the
default controller for any board whose machine types are versioned.

Paolo