Re: Paravirtualizing bits of acpi access

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Sunday 22 March 2009, Ingo Molnar wrote:
> 
> * Rafael J. Wysocki <rjw@sisk.pl> wrote:
> 
> > On Sunday 22 March 2009, Jeremy Fitzhardinge wrote:
> > > Rafael J. Wysocki wrote:
> > > > Well, why don't you implement the platform suspend operations for Xen?
> > > > I guess you don't want ACPI _PTS to be executed during suspend as well.
> > > >   
> > > 
> > > I don't know.  What's _PTS?
> > 
> > It's an ACPI method called to prepare the platform to enter the sleep state
> > (the name stands for "prepare to sleep").  Executing it may affect the
> > hardware.
> > 
> > > I think for the most part we want Linux to do most of the acpi 
> > > work of bringing the machine into an idle state.  Its just that 
> > > Xen is responsible for the very low level cpu context 
> > > save/restore, because the Linux kernel is still running on vcpus 
> > > rather than the physical cpus.
> > 
> > I think you really should not execute any global ACPI methods to 
> > suspend a guest, because that may affect the host.  That's why I 
> > think it's better to regard Xen as a platform and implement a 
> > separate set of suspend operations for it.
> 
> I'd agree with that. That also allows the reuse of existing 
> callbacks, right?

Yes, it does.

Rafael