Re: [Xen-devel] [PATCH 5/7] xen/arm: wake up secondary cpus

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 26 Oct 2012, Ian Campbell wrote:
> On Fri, 2012-10-26 at 12:18 +0100, Stefano Stabellini wrote:
> > On Fri, 26 Oct 2012, Ian Campbell wrote:
> > > On Thu, 2012-10-25 at 18:45 +0100, Stefano Stabellini wrote:
> > > > > >  
> > > > > >  boot_cpu:
> > > > > > @@ -98,6 +98,10 @@ boot_cpu:
> > > > > >     PRINT(" booting -\r\n")
> > > > > >  #endif
> > > > > >  
> > > > > > +   /* Wake up secondary cpus */
> > > > > > +   teq   r12, #0
> > > > > > +   bleq  kick_cpus
> > > > > 
> > > > > Does this have to be done this early? Couldn't we defer it to C land
> > > > > where it would be easier to isolate the processor/platform specific
> > > > > behaviour?
> > > > 
> > > > Yes, it does because we need to send an interrupt to cpus running in
> > > > secure mode, so this has to happen before we drop off secure state and 
> > > > we
> > > > enter hypervisor state.
> > > 
> > > Hrm, so maybe this stuff does belong in mode_switch.S after all?
> > > 
> > > Or is there perhaps some register (e.g. in the GIC?) which would allow
> > > non-secure hyp mode to sent an event to a processor in secure monitor
> > > mode?
> > 
> > Whether the target processor in secure mode receives the interrupt or
> > not, depends only on the GIC configuration on the target processor.
> > I don't think there is anything we can do from cpu0 in non-secure mode.
> 
> Isn't this controlled by the GICD_GROUP register, which can be set from
> cpu0 but affects all cpus?

GICD_GROUP0 is banked


> Or is it the case that we need to do this poke before mode_switch.S
> makes all interrupts into grp1 interrupts?

I don't think we can do that, it is the receiver cpu that would need to
do it

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