Re: [Xen-devel] ARM Generic Timer interrupt

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2014-05-27 at 13:11 +0100, Stefano Stabellini wrote:
> > But, I have question:
> > Should the Hypervisor masks virtual timer IRQ on his own?
> > It is a guest's resource and the guest itself should decide what to do.
> > For example, I see that Linux Kernel (3.8) sets and clears timer interrupt 
> > mask by itself.
> 
> In principle I agree with you that the vtimer is a guest resource.
> However in practice if we don't mask the irq we can easily get into an
> interrupt storm situation: if the guest doesn't handle the interrupt
> immediately we could keep receiving the vtimer irq in the hypervisor and
> busy loop around it.

Do we not do a priority drop on the interrupt when we receive it, so we
won't get any more interrupts from the timer until it acks the
interrupt?

Just to be clear: The behaviour of the physical timer is not that it is
automatically masked when it fires?

Ian.


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