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Re: [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments
From: |
Alexander Graf |
Subject: |
Re: [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments |
Date: |
Tue, 11 Jan 2011 15:06:40 +0100 |
On 11.01.2011, at 15:00, Anthony Liguori wrote:
> On 01/11/2011 03:01 AM, Avi Kivity wrote:
>> On 01/10/2011 10:23 PM, Anthony Liguori wrote:
>>>>> I don't see how ioapic, pit, or pic have a system scope.
>>>> They are not bound to any CPU like the APIC which you may have in mind.
>>>
>>> And none of the above interact with KVM.
>>
>> They're implemented by kvm. What deeper interaction do you have in mind?
>
> The emulated ioapic/pit/pic do not interact with KVM at all.
>
> The KVM versions should be completely separate devices.
>
>>
>>>
>>> They may be replaced by KVM but if you look at the PIT, this is done by
>>> having two distinct devices. The KVM specific device can (and should) be
>>> instantiated with kvm_state.
>>>
>>> The way the IOAPIC/APIC/PIC is handled in qemu-kvm is nasty. The kernel
>>> devices are separate devices and that should be reflected in the device
>>> tree.
>>
>> I don't see why. Those are just two different implementations for the same
>> guest visible device.
>
> Right, they should appear the same to the guest but the fact that they're two
> different implementations should be reflected in the device tree.
>
>> It's like saying IDE should be seen differently if it's backed by qcow2 or
>> qed.
>
> No, it's not at all.
>
> Advantages of separating KVM devices:
>
> 1) it becomes very clear what functionality is handled in the kernel verses
> in userspace (you can actually look at the code and tell)
>
> 2) a user can explicitly create either the emulated version of the device or
> the in-kernel version of the device (no need for -no-kvm-irqchip)
>
> 3) a user can pass parameters directly to the in-kernel version of the device
> that are different from the userspace version (like selecting different
> interrupt catch-up methods)
Disadvantages:
1) you lose migration / savevm between KVM and non-KVM VMs
I'm not saying this is unsolvable, but it's certainly something that bothers me
:). Some sort of meta-device for KVM implemented devices and emulated devices
would be nice. That device would then be the one state gets saved/restored from.
Alex
- [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments, (continued)
- [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments, Anthony Liguori, 2011/01/06
- [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments, Jan Kiszka, 2011/01/07
- [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments, Anthony Liguori, 2011/01/07
- [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments, Jan Kiszka, 2011/01/08
- [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments, Anthony Liguori, 2011/01/10
- [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments, Jan Kiszka, 2011/01/10
- Re: [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments, Anthony Liguori, 2011/01/10
- Re: [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments, Jan Kiszka, 2011/01/10
- Re: [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments, Avi Kivity, 2011/01/11
- Re: [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments, Anthony Liguori, 2011/01/11
- Re: [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments,
Alexander Graf <=
- Re: [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments, Anthony Liguori, 2011/01/11
- Re: [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments, Avi Kivity, 2011/01/11
- Re: [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments, Anthony Liguori, 2011/01/11
- Re: [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments, Avi Kivity, 2011/01/11
- Re: [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments, Anthony Liguori, 2011/01/11
- Re: [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments, Alexander Graf, 2011/01/11
- Re: [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments, Avi Kivity, 2011/01/11
- Re: [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments, Anthony Liguori, 2011/01/11
- Re: [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments, Avi Kivity, 2011/01/11
- Re: [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments, Anthony Liguori, 2011/01/11