Gregory Haskins wrote:
> Agreed. I was thinking that the interface for the "IOAPIC in kernel" model
> would look something like the way the pic_send_irq() function looks, except
> it would also convey BUS/IOAPIC id.
>
> so: kvm_inject_interrupt(int bus, int pin, int value);
>
> and the "kvmpic" driver would currently translate as bus = 0 (giving us
> IRQ0-23). E.g.
>
> kvmpic_send_irq(int irq, int value)
> {
> kvm_inject_interrupt(0, irq, value);
> }
>
With appropriate modeling of edge vs level triggered, and translation of
pin to vector, yes.
>
>
>> Everything should keep working, that is a must. We just need the
>> interfaces to follow the hardware faithfully. The issue with the ioapic
>> eoi is worrying me performance wise, though; it looks like we need to
>> push the ioapic too if we are to have no- compromise performance on
>> unmodified OSes.
>>
>
> Not sure if this will make you feel better, but it appears as though both the
> QEMU and the in-kernel model that I inherited don't accurately support IOAPIC
> EOI already. From that you can infer that there must not be any
> level-sensitive interrupts in use today. Since the system seems to only have
> the legacy ISA model (which dictates edge triggers, IIRC), this makes sense.
> However, if we want to support level triggers in the future, we will have to
> address this. I would be uncomfortable designing something that doesn't take
> the IOAPIC EOI into account, even if its not immediately used.
>
>
pci is level triggered, so maybe the guests just handle the inaccuracy.
>> For unmodified guests, use the existing pci irq routing. I certainly
>> wouldn't want to debug anything else. For modified guests, there's no
>> real problem.
>>
>
> Ill take your word for it ;) I spent a few minutes looking through the linux
> kernel trying to figure out how to get a hint about a free vector without
> assigning one statically in the header files and came up empty handed. Im
> sure there is a way (or maybe static is ok?).
>
>
No idea really, but the paravirt_ops stuff probably provides the right
hooks.
--
error compiling committee.c: too many arguments to function
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