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

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 29 Mar 2013, Nicolas Pitre wrote:
> On Fri, 29 Mar 2013, Stefano Stabellini wrote:
> 
> > If PSCI initializes correctly and PSCI SMP operations are available, use 
> > them.
> > This is required for SMP support in Dom0 on Xen.
> > 
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > CC: will.deacon@xxxxxxx
> > CC: arnd@xxxxxxxx
> > CC: marc.zyngier@xxxxxxx
> > CC: linux@xxxxxxxxxxxxxxxx
> > CC: nico@xxxxxxxxxx
> 
> I'd suggest you also include in your series the patch I posted earlier 
> providing a runtime mdesc->smp_init method as well.

OK.


> 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.

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