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Re: [Xen-devel] [PATCH v4 14/18] xen/arm: IRQ: Store IRQ type in arch_irq_desc

On Fri, 2014-05-02 at 09:49 +0100, Julien Grall wrote:
> Hi Ian,
> Sorry for the delay, for some unknown reason I skipped this mail.
> On 23/04/14 15:04, Ian Campbell wrote:
> >> +         * CPU0 otherwise we may miss the type if the IRQ type has been
> >> +         * set early.
> >
> > what does "set early" mean, how early is early? Initialised before
> > secondary CPUs were brought up perhaps?
> Yes. I will replace "set early" by "initialised before secondary CPUs 
> were brought up"
> >
> >          /* PPIs are included in local_irqs, we copy the IRQ type from
> >           * CPU0 when bringing up secondary cpus in order to pick up any
> >           * configuration done before this CPU came up. For interrupts
> >           * configured after this point this is done in XXX().
> I guess you suggest to replace the previous comment by this one, right?

If it is factually accurate, yes.

> > Why is the copying not conditional on CPU!=0?
> As the CPU were not online (therefore its per_cpu regions is not there) 
> at the time we setup the IRQ we have to unconditionally set the IRQ type.

But CPU0 must have been online when we setup the IRQ.

IOW if CPU==0 then isn't 
        desc->arch.type = per_cpu(local_irq_desc, 0)[irq].arch.type;
equivalent to
        desc->arch.type = desc->arch.type


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