On 04.07.2010, at 11:17, Alexander Graf wrote:
>
> On 04.07.2010, at 11:10, Avi Kivity wrote:
>
>> On 07/04/2010 12:04 PM, Alexander Graf wrote:
>>>
>>> My biggest concern about putting things in the device-tree is that I was
>>> trying to keep things as separate as possible. Why does the firmware have
>>> to know that it's running in KVM?
>>
>> It doesn't need to know about kvm, it needs to know that a particular
>> hypercall protocol is available.
>
> Considering how the parts of the draft that I read about sound like, that's
> not the inventor's idea. PPC people love to see the BIOS be part of the
> virtualization solution. I don't. That's the biggest difference here and
> reason for us going different directions.
>
> I think what they thought of is something like
>
> if (in_kvm()) {
> device_tree_put("/hypervisor/exit", EXIT_TYPE_MAGIC);
> device_tree_put("/hypervisor/exit_magic", EXIT_MAGIC);
> }
>
> which then the OS reads out. But that's useless, as the hypercalls are
> hypervisor specific. So why make the detection on the Linux side generic?
In fact, it's even worse. Right now with KVM for PPC we have 3 different ways
of generating the device tree:
1) OpenBIOS (Mac emulation)
2) Qemu libfdt (BookE)
3) MOL OF implementation
So I'd have to touch even more projects. Just for the sake of splitting out
something that belongs together anyway. And probably even create new interfaces
just for that sake (qemu asking the kernel which type of hypercalls the vm
should use) even though the guest could just query all that itself.
Alex
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