Re: [Qemu-devel] Re: [PATCH v2 4/9] provide in-kernel apic

[Anthony Liguori <aliguori@us.ibm.com>]

Jamie Lokier wrote:
> Glauber Costa wrote:
>   
>> On Fri, Oct 09, 2009 at 11:06:41AM +0100, Jamie Lokier wrote:
>>     
>>> Glauber Costa wrote:
>>>       
>>>>> It ensures the two models are compatible.  Since they're the same device  
>>>>> from the point of view of the guest, there's no reason for them to have  
>>>>> different representations or to be incompatible.
>>>>>           
>>>> live migration between something that has in-kernel irqchip and
>>>> something that has not is likely to be a completely untested
>>>> thing. And this is the only reason we might think of it as the same
>>>> device. I don't see any value in supporting this combination
>>>>         
>>> Not just live migration.  ACPI sleep + savevm + loadvm + ACPI resume,
>>> for example.
>>>       
>> Yes, but in this case too, I'd expect the irqchipness of qemu not to change.
>>     
>
> If I've just been sent an image produced by someone running KVM, and
> my machine is not KVM-capable, or I cannot upgrade the KVM kernel
> module because it's in use by other VMs (had this problem a few
> times), there's no choice but to change the irqchipness.
>   

You cannot migrate from KVM to TCG so this use-case is irrelevant.


-- 
Regards,

Anthony Liguori