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Re: [Qemu-devel] [PATCH v5 06/16] apic: Introduce backend/frontend infra

From: Jan Kiszka
Subject: Re: [Qemu-devel] [PATCH v5 06/16] apic: Introduce backend/frontend infrastructure for KVM reuse
Date: Wed, 21 Dec 2011 00:45:43 +0100
User-agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv: Gecko/20080226 SUSE/ Thunderbird/ Mnenhy/

On 2011-12-21 00:41, Anthony Liguori wrote:
> On 12/20/2011 04:20 PM, Jan Kiszka wrote:
>> On 2011-12-20 22:55, Anthony Liguori wrote:
>>> The components of the path are the *property* names of the parent
>>> device.  In the case of the local APIC, you would have something like:
>>> /cpus/cpu0/apic
>>> /cpus/cpu1/apic
>>> Which would be links on the composition tree.  The name wouldn't change
>>> even if the type of this object changed.
>> Perfect! That was what I forgot about and what makes it possible to
>> return to the original two-device model.
>>> You'll probably have a flag or
>>> something in the cpu object that lets you determine whether the child is
>>> created as a kvm-apic or just a normal apic.
>> I rather hope you will be able to ask the device for its type instead
>> replicating that information.
> Yes, but that's not what I was getting at.
> I think you are currently planning on enabling/disabling the in-kernel
> apic through a machine option?

Yes, because it is a VM-wide flag, nothing you can control per irqchip,
per chipset or whatever. It must be consistent for the whole VM, means
all CPUs, the chipset, the IOAPIC (which may or may not (PIIX3) be part
of it) etc. It also affects KVM internals that are not directly bound to
device models.


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