Re: [Qemu-devel] [PATCH v3 4/5] xics: directly register ICPState objects to vmstate

[David Gibson]

On Wed, Jun 07, 2017 at 07:17:17PM +0200, Greg Kurz wrote:
> The ICPState objects are currently registered to vmstate as qdev objects.
> Their instance ids are hence computed automatically in the migration code,
> and thus depends on the order the CPU cores were plugged.
> 
> If the destination had its CPU cores plugged in a different order than the
> source, then ICPState objects will have different instance_ids and load
> the wrong state.
> 
> Since CPU objects have a reliable cpu_index which is already used as
> instance_id in vmstate, let's use it for ICPState as well.
> 
> Signed-off-by: Greg Kurz <address@hidden>
> ---
>  hw/intc/xics.c |    5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)

So, this is definitely a good idea w.r.t. future compatibility.  But,
won't it break migration compat as a once off, since the devices will
be found under their new id instead of the qdev id?

> 
> diff --git a/hw/intc/xics.c b/hw/intc/xics.c
> index 330441ff7fe8..3d76b43876c5 100644
> --- a/hw/intc/xics.c
> +++ b/hw/intc/xics.c
> @@ -348,10 +348,14 @@ static void icp_realize(DeviceState *dev, Error **errp)
>      }
>  
>      qemu_register_reset(icp_reset, dev);
> +    vmstate_register(NULL, icp->cs->cpu_index, &vmstate_icp_server, icp);
>  }
>  
>  static void icp_unrealize(DeviceState *dev, Error **errp)
>  {
> +    ICPState *icp = ICP(dev);
> +
> +    vmstate_unregister(NULL, &vmstate_icp_server, icp);
>      qemu_unregister_reset(icp_reset, dev);
>  }
>  
> @@ -359,7 +363,6 @@ static void icp_class_init(ObjectClass *klass, void *data)
>  {
>      DeviceClass *dc = DEVICE_CLASS(klass);
>  
> -    dc->vmsd = &vmstate_icp_server;
>      dc->realize = icp_realize;
>      dc->unrealize = icp_unrealize;
>  }
> 

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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