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

[Alexander Graf <agraf@suse.de>]

On 07/19/2012 04:16 PM, Peter Maydell wrote:
> On 19 July 2012 15:13, Alexander Graf <agraf@suse.de> wrote:
>> On 07/19/2012 02:00 PM, Peter Maydell wrote:
>>> On 19 July 2012 12:43, Avi Kivity <avi@redhat.com> 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.

Or we just remove the !in_kernel path for x86. Then everyone else can be 
asynchronous even for user space interrupt controller emulation.


Alex