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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2014-07-24 at 11:36 +0100, Julien Grall wrote:
> 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:
> â Each secondary CPUâs cpu node shall have a status property with a 
> value of âdisabledâ.

Oh well, it was only a convenience for me anyway.
Ian

> 
> Regards,
> 



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