Re: KVM in-kernel APIC update

["Gregory Haskins" <ghaskins-Et1tbQHTxzrQT0dZR+AlfA@public.gmane.org>]

>>> 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.....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.


> 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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