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

From: Alexander Graf
Subject: Re: [Qemu-devel] passing interrupts from QEMU to KVM
Date: Thu, 19 Jul 2012 16:30:43 +0200
User-agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:14.0) Gecko/20120713 Thunderbird/14.0

On 07/19/2012 04:16 PM, Peter Maydell wrote:
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.

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


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