Re: [Qemu-devel] Snapshots not bound to an architecture?

[Anthony Liguori <anthony@codemonkey.ws>]

Paul Brook wrote:
> On Tuesday 07 October 2008, Anthony Liguori wrote:
>   
>> Blue Swirl wrote:
>>     
>>> Hi,
>>>
>>> While testing the savevm/loadvm functions, I noticed that it's
>>> possible to attempt to load a snapshot made for entirely different
>>> architecture. There are a lot of warnings, of course.
>>>
>>> Could we prevent this somehow? Or is there a use case for this, for
>>> example loading a snapshot made on i386 to an x86_64 emulator?
>>>       
>> I think we should introduce a machine section for save/restore that
>> included that information.  It should also be versioned in such a way
>> that it could be incremented whenever a new piece of hardware is added
>> to the default machine type.
>>     
>
> Using a single version number to determine the "base" machine is IMHO a bad 
> idea.

I should have said, that I expected this to be an intermediate step.

>  The base peripherals should be identified (and mismatches detected) 
> that same way as any other peripherals.
>   

Yes.  This is particularly important in the context of hot plug because 
the bus/dev/fn of the plugged device may be different than if the device 
were just added directly.

> The simplest way to avoid loading the wrong type of machine is to give the 
> cpus different names (e.g. cpu_i386/cpu_amd64) instead of just calling 
> them "cpu".
>   

Yes, that works too, but it breaks backwards compatibility in a way 
that's hard to reconcile.  Bumping the version of "cpu" and including a 
machine type identifier would also work and would be easier to do in a 
backwards compatible way.

Regards,

Anthony Liguori

> Paul
>