[Qemu-devel] Re: [PATCH] vmstate: fix vmstate_subsection_load

[TeLeMan]

On Wed, Jul 28, 2010 at 18:43, Juan Quintela <address@hidden> wrote:
> TeLeMan <address@hidden> wrote:
>>  If the new version adds the new subsection for some vmstate, the old
>> version will load the new version's vmstate unsuccessfully. So we have
>> to ignore the unrecognized subsections.
>
> No.  That was the whole point of subsections.  If one subsection is
> sent, target machine has to understand it.  If it don't understand it,
> it fails.
>
> If subsection is not needed, it is the responsability of the source to
> not send it.
>
> This was one of the design requirements.  Subsections are optional but
> it is the source which decides which ones to send/not to send.  The
> target has to understand everything that it gets or fail the migration.
>

If the target must understand everything, the vmstate's version will
be useless because the old version target maybe cannot load the new
version target's vmstate.