Re: NetBSD Dom0 and (kind of) power management

[Christoph Egger <Christoph_Egger%gmx.de@localhost>]

On 18.03.11 08:34, Jukka Ruohonen wrote:
> On Fri, Mar 18, 2011 at 07:54:47AM +0100, Christoph Egger wrote:
>> The key point is that the Dom0 has virtual cpus. And you don't know
>> which vcpu is scheduled on which physical cpu.
>>
>> Dom0 has to invoke hypercalls for all kind of things that must happen
>> on the physical cpus.
>> C- and P-States belong to those "things".
> 
> That is of course the basic scheme.
> 
> But when reading the hypervisor code and looking at some Intel's presentations
> (see e.g. [1]), the Xen 4.0 hypervisor implements (or rather, duplicates) its
> own full-blown, Linux-dependent, CPU PM facility.
> 
> From the x86 and ACPI standpoint this seems to imply that not only are the
> basic things like hypercalls necessary, but we would have to implement normal
> x86 drivers and interfaces to match the ever-changing Linux/Xen APIs. I don't
> think that is desirable, so in my opinion the old "dom0-based" approach is
> more reasonable for NetBSD.

We can always speak up on xen-devel and say why this or that hypercall
is bad along with a proposal that fits for NetBSD.

> - Jukka.
> 
> [1] http://www.xen.org/files/xensummit_oracle09/XenSummit09pm.pdf
>