Re: [PATCH 27/27] KVM: PPC: Add Documentation about PV interface

On 04.07.2010, at 11:17, Alexander Graf wrote:

=20
On 04.07.2010, at 11:10, Avi Kivity wrote:
=20

quoted

On 07/04/2010 12:04 PM, Alexander Graf wrote:

quoted

=20
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?

quoted

=20
It doesn't need to know about kvm, it needs to know that a particular =

hypercall protocol is available.

=20
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.

=20
I think what they thought of is something like
=20
if (in_kvm()) {
 device_tree_put("/hypervisor/exit", EXIT_TYPE_MAGIC);
 device_tree_put("/hypervisor/exit_magic", EXIT_MAGIC);
}
=20
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