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

[Avi Kivity <avi@redhat.com>]

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.

> Most importantly though, the code should reflect how things behave.  
> It's extremely difficult to look at the apic code and figure out what 
> bits are used and what bits aren't used when the in-kernel apic is 
> enabled.

That doesn't mean they need to be separate devices.

-- 
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