Re: KVM in-kernel APIC update

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Gregory Haskins wrote:
>>>> On Wed, Apr 4, 2007 at  4:32 PM, in message <20070404203235.GA11369-X9Un+BFzKDI@public.gmane.org>,
>>>>         
> Ingo Molnar <mingo-X9Un+BFzKDI@public.gmane.org> wrote: 
>   
>>> My current thoughts are that we at least move the IOAPIC into the 
>>> kernel as well. [...]
>>>       
>> yes. And then do the final 10% move of handling the i8529A in KVM too. 
>>     
>
> Hi Ingo,
>   We are in full agreement on this point, and has been my preferred model from the beginning.  The only issue with this approach is that it requires a fairly disruptive patch to QEMUs "pic_set_irq()" feature which many people have drawn exception to so far.  (In case you weren't following from the beginning, its the "QEMU PIC indirection patch...." thread). 
>   

You can hack it with if (use_kvm) { ... } (or, more likely, 
use_kvm_platform_/


> If we dont care about supporting "--no-kvm" anymore, this problem becomes trivially easy.....we can just link in a different pic module into QEMU and be done with it.  The problem as I see it is that we really have a lot of value in being able to switch between kvm and pure qemu mode via --no-kvm, especially for debugging.  Therefore, IMHO we need to be able to dynamically switch between PIC emulation code.  
>
>   

-no-kvm is critical, it's an important debugging tool.  Also keeping 
emulation in qemu is important for <= 2.6.21 (or maybe 22) users, which 
will not have the in-kernel platform devices.

> If we *do* want to go with this model, *and* we decide that the approach I have taken with QEMU is a reasonable way to do it, then I would suggest we go about it by getting the patch accepted in QEMU upstream.  I would gladly take on this duty if we all agree this is the right approach.
>   

I think getting the patch in is beneficial.  Perhaps after re-review in 
light of all the discussion.



-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.


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