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Date: Tue, 20 Dec 2011 14:57:39 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v5 06/16] apic: Introduce backend/frontend
 infrastructure for KVM reuse
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: kvm@vger.kernel.org, "Michael S. Tsirkin" <mst@redhat.com>, Marcelo Tosatti <mtosatti@redhat.com>, qemu-devel <qemu-devel@nongnu.org>, Blue Swirl <blauwirbel@gmail.com>, Jan Kiszka <jan.kiszka@web.de>, Avi Kivity <avi@redhat.com>

On 12/20/2011 02:54 PM, Anthony Liguori wrote:
>> In QOM parlance Jan implemented this:
>>
>> abstract class Object
>>     abstract class Device
>>         class APIC: { backend: link<APICBackend> }
>>     abstract class APICBackend
>>         class QEMU_APICBackend
>>         class KVM_APICBackend
>
> I don't fundamentally object to modeling it like this provided that it's
> modeled (and visible) through qdev and not done through a one-off
> infrastructure.

There is no superclass of DeviceState, hence doing it through qdev would 
mean introducing a new bus type and so on.  This would be a superb 
example of a useless bus that can disappear with QOM, but I don't see 
why we should take the pain to add it in the first place. :)

We sure can revisit this when the subclassing and interface 
infrastructures of QOM are merged.

Paolo