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

[Juan Quintela]

Paolo Bonzini <address@hidden> wrote:
> On 07/28/2010 02:51 PM, TeLeMan wrote:

> Even if they are mandatory, subsections still improve the situation
> here, because they provide a clean way to "branch" off an upstream
> vmstate version.  At least the failure will be clear, because an
> unsupported subsection is easily detected when migrating to (or
> restoring with) upstream.
>
> Instead, for example RHEL5.5's "version 9" cpu save format will often
> crash upstream version 9 with a SIGSEGV.

Old kvm (pre start of merge with qemu) and qemu device versions are out
of sync.  You can't migrate between them at all.  Basically you can't
migrate from anything older than qemu-0.12.  In qemu-0.12 firmware for
devices got moved to pci bars and memory layout changed in such a way
that it is not compatible at all.

Later, Juan.