Re: [Xen-devel] [PATCH v8 03/10] xen/arm: inflight irqs during migration

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 24 Jul 2014, Ian Campbell wrote:
> On Thu, 2014-07-24 at 17:45 +0100, Stefano Stabellini wrote:
> > > Are you sure about the second physical IRQ always hitting on the source
> > > pCPU though? I'm unclear about where the physical ITARGETSR gets written
> > > in the scheme you are proposing.
> > 
> > It gets written right away if there are no inflight irqs.
> 
> There's no way that something can be pending in the physical GIC at this
> point? i.e. because it happened since we took the trap?

If it is pending is OK: ARM ARM states that writes to itarget affect
pending irqs too. Only active irqs are not affected. But we deal with
that case separately.


> >  Otherwise it
> > gets written when clearing the LRs. That's why we are sure it is going
> > to hit the old cpu. If the vcpu gets descheduled after EOIing the irq,
> > that is also fine because Xen is going to clear the LRs on hypervisor
> > entry.
> 
> Ian.
> 

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