Re: [Xen-devel] [PATCH v4 07/10] xen/arm: call gic_clear_lrs on entry to the hypervisor

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 21 Mar 2014, Ian Campbell wrote:
> On Wed, 2014-03-19 at 12:32 +0000, Stefano Stabellini wrote:
> 
> Can this not be folded back into the patch which added this function?

Yes, it can.


> > This change is needed by other patches later on. It is going to make
> > sure that the calculation in Xen of the highest priority interrupt
> > currently inflight is correct and accurate and not based on stale data.
> 
> Hrm, can we not do this on demand just at the point where we are about
> to make such a calculation? There are going to be lots of hypervisor
> entries which don't want to do anything at all with interrupts, aren't
> there?

The alternative would be calling gic_clear_lrs at the beginning of
gic_inject and gic_events_need_delivery, that is called by
local_events_need_delivery*.  It could be called multiple times before
returning to guest.

However gic_clear_lrs only iterates over the LRs in lr_mask, so even
calling it multiple times shouldn't cause more work, the only slow down
would be due to the spin_lock.

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