Re: [Xen-devel] [PATCH] xen: arm: ignore CPUs which are not marked available in the DT

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi Ian,

On 23/07/14 19:36, Ian Campbell wrote:
> On Wed, 2014-07-23 at 18:15 +0100, Julien Grall wrote:
> > On 07/23/2014 05:45 PM, Ian Campbell wrote:
> > > Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> > > ---
> > >   xen/arch/arm/smpboot.c |    3 +++
> > >   1 file changed, 3 insertions(+)
> > >
> > > diff --git a/xen/arch/arm/smpboot.c b/xen/arch/arm/smpboot.c
> > > index cf149da..4b0a738 100644
> > > --- a/xen/arch/arm/smpboot.c
> > > +++ b/xen/arch/arm/smpboot.c
> > > @@ -134,6 +134,9 @@ void __init smp_init_cpus(void)
> > >           if ( !dt_device_type_is_equal(cpu, "cpu") )
> > >               continue;
> > >
> > > +        if ( !dt_device_is_available(cpu) )
> > > +            continue;
> > > +
> > I can't find a such things on the Linux device tree bindings.
> status is a generic property which is common to all nodes, it comes from
> ePAPR.
>
> >   Do you
> > have a use case where CPU are marked disabled?
> I use it locally when booting with models -- it allows me to turn off
> cpus in the base .dts file using a wrapper instead of having to edit the
> original.
I read the ePAPR and the property status on CPU node. AFAIU, the 
property doesn't have this meaning for a such node.
This property means the CPU is in quiescent state and property to bring 
up the CPU is provides in the device tree node.
Section 5.5.2.2:

Before starting a client program on the boot cpu, the boot program shall 
set certain properties in the
device tree passed to the client as follows:
• Each secondary CPU’s cpu node shall have a status property with a 
value of “disabled”.
Regards,

--
Julien Grall

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