Re: [Xen-devel] [PATCH v4 2/2] arm: prefer PSCI for SMP bringup

[Nicolas Pitre <nicolas.pitre@xxxxxxxxxx>]

On Fri, 29 Mar 2013, Stefano Stabellini wrote:

> On Fri, 29 Mar 2013, Nicolas Pitre wrote:
> > This way the 
> > priority order would be:
> > 
> > - If mdesc->smp_init is non null then use that.
> > 
> > - Otherwise, if PSCI is available then use that.
> > 
> > - Otherwise use mdesc->smp.
> > 
> > This way, if the PSCI default has to be overriden (like in the MCPM case 
> > because it needs to wrap PSCI itself, or to cover Rob's concern) then 
> > this can be achieved at run time on a per mdesc basis.
> 
> Actually that's not a bad idea, it could make everybody happy.
> What about the following, in this precise order:
> 
> - if a xen hypervisor node is present on device tree, use PSCI;
> - otherwise if mdesc->smp_init is non null then use it;
> - otherwise if PSCI is available then use it;
> - otherwise use mdesc->smp.
> 
> It's the most practical solution to satisfy everybody's needs.

Regardless of my previous email suggesting a mdesc for xen, I still 
don't understand why you need this absolute priority for Xen.  Isn't my 
original suggestion sufficient?

The likely reason why mdesc->smp_init might be needed is to provide an 
extra encapsulation layer before actually using PSCI instead of using it 
directly.  Why would you need to bypass that?


Nicolas

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