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

[Glauber Costa]

On Thu, Oct 08, 2009 at 04:31:57PM +0200, Avi Kivity wrote:
> On 10/08/2009 04:26 PM, Anthony Liguori wrote:
>> Avi Kivity wrote:
>>> On 10/08/2009 03:55 PM, Anthony Liguori wrote:
>>>>
>>>> You should probably just setup VMState such that it directly saves  
>>>> kvm_lapic_state and then have the pre/post functions call the 
>>>> kernel ioctls to sync it.  There's not a whole lot of point 
>>>> switching the state between two different structures.
>>>
>>> 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.
>>
>> The problem is, the in-kernel apic is not part of the qemu source  
>> tree.  If we add a field to the qemu apic, then we would break the  
>> in-kernel apic and vice-versa.  It's far easier to just have the  
>> in-kernel apic as a separate model.
>>
>
> You need to handle it anyway due to save/restore; that is the new field  
> and whatever functionality it has must be optional.
Not necessarily. You can grab the structures directly from the kernel definition
, copy that over, issue the ioctl, and just make sure the source and destination
have compatible kernels.