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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 16:17:55 +0100 |
On 11.01.2011, at 16:12, Anthony Liguori wrote:
> On 01/11/2011 08:56 AM, Avi Kivity wrote:
>> On 01/11/2011 04:36 PM, Anthony Liguori wrote:
>>>> They need to use the same device id then. And if they share code, that
>>>> indicates that they need to be the same device even more.
>>>
>>>
>>> No, it really doesn't :-) Cirrus VGA and std VGA share a lot of code. But
>>> that doesn't mean that we treat them as one device.
>>
>> Cirrus and VGA really are separate devices. They share code because on
>> evolved from the other, and is backwards compatible with the other. i8254
>> and i8254-kvm did not evolve from each other,
>
> Actually, they did, but that's besides the point.
>
>> both are implementations of the i8254 spec, and both are 100% compatible
>> with each other (modulu bugs).
>>
>>>
>>> And BTW, there are guest visible differences between the KVM IOAPIC/PIC/PIT
>>> than the QEMU versions. The only reason PIT live migration works today is
>>> because usually delivers all interrupts quickly. But it actually does
>>> maintain state in the work queue that isn't saved. If PIT tried to
>>> implement gradual catchup, there would be no way not to expose that state
>>> to userspace.
>>
>> Why not? Whatever state the kernel keeps, we expose to userspace and allow
>> sending it over the wire.
>
> What exactly is the scenario you're concerned about?
>
> Migration between userspace HPET and in-kernel HPET?
>
> One thing I've been considering is essentially migration filters. It would
> be a set of rules that essentially were "hpet-kvm.* = hpet.*" which would
> allow migration from hpet to hpet-kvm given a translation of state. I think
> this sort of higher level ruleset would make it easier to support migration
> between versions of the device model.
>
> Of course, that only gives you a forward path. It doesn't give you a
> backwards path.
Why not? Just include the version in the rule set and define a backwards rule
if it's easy to do. If not, migration isn't possible.
Alex
- Re: [Qemu-devel] Re: [PATCH 26/35] kvm: Eliminate KVMState arguments, (continued)
- 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, 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, 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, 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, Avi Kivity, 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, 2011/01/10