[Xen-devel] Re: Paravirtualizing bits of acpi access

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

Rafael J. Wysocki 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.
>   
OK, that's what we want.  Dom0 is the control domain which is 
responsible for the bulk of the hardware; Xen itself has very little 
hardware knowledge.
> 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.
>   
In this case we're talking about the special privileged domain which can 
be considered to be on the "host" side of the line. 

That said, I'd be interested in looking at a suspend operations-based 
approach if you think its the right way to go.  But I'm concerned that 
we'd end up with a big set of very similar-looking parallel functions 
just to deal with some difference in detail near the bottom.  Can you 
give me a pointer to where this gets put together for acpi?
Thanks,
   J

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