Re: [Qemu-devel] passing interrupts from QEMU to KVM

[Peter Maydell]

On 19 July 2012 15:13, Alexander Graf <address@hidden> wrote:
> On 07/19/2012 02:00 PM, Peter Maydell wrote:
>> On 19 July 2012 12:43, Avi Kivity <address@hidden> wrote:
>>> Let's make them even more similar, by removing !in_kernel_irqchip.
>>
>> Mmm, I do rather want to just mandate use of the VGIC...
>> (somebody will probably come along later and try to get A9
>> guests working with KVM acceleration but I don't think it
>> will be me :-))
>
> Heh. I would really like to keep the !in_kernel_irqchip path (so only an EXT
> IRQ line exposed) available for PPC at least. It has helped tremendously in
> the past to be able to just throw a few debug printfs into QEMU and/or
> compare with TCG what's happening when things go wrong.

I think the difficulty here is that QEMU's in_kernel_irqchip
test is being used for two things:
 * which APIC model etc should we use?
 * details of the synchronous vs asynchronous model (for instance
whether halt is handled by cpus.c depends on this: cpu_thread_is_idle
always returns false if kvm_irqchip_in_kernel())

because for x86 these two things happen for historical reasons
to be in sync. The non-x86 architectures probably need to separate
them out so that we are always using the 'asynchronous inject'
model but may (architecture-dependent) allow the user to pick
which irqchip model gets used.

-- PMM