Re: KVM in-kernel APIC update

[Anthony Liguori <aliguori-r/Jw6+rmf7HQT0dZR+AlfA@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). 
>
> If we dont care about supporting "--no-kvm" anymore, this problem becomes trivially easy.....

No, this would be a big mistake.  We'll just end up with another qemu-dm.

> 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.  
>
> 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 you should post the patch on qemu-devel if for nothing else to 
begin the discussion.

Regards,

Anthony Liguori

>   
>> for PV/accel drivers we dont need any extra ACPI enumeration -  the 
>> hypercall API is good enough to connect to the hypervisor, and i suspect 
>> all guest OSs we care about allow drivers to allocate an IRQ vector for 
>> a new device, without having that device enumerated in ACPI.
>>     
>
> If you know how to do this in Linux, please share!  I was looking for this earlier and came up empty handed.  All I could find was the places where the PCI/MP/ACPI type things assigned vectors to devices they new about.  It's probably "operator-ignorance" ;)
>
> Regards,
> -Greg
>
>
>
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