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Re: [Xen-devel] Interrupt synchronisation and HVM

To: James Harper <james.harper@xxxxxxxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Interrupt synchronisation and HVM
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Fri, 25 Jul 2008 07:56:02 +0100
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The evtchn_upcall_mask is not respected for HVM guests. When you set
HVM_PARAM_CALLBACK_IRQ to 0, no more interrupts will be generated at the PIC
or IO-APIC. But any interrupts queued up at either of those will eventually
get propagated to the CPU. Is there a way to de-register from an IRQ and
hence get Windows to mask the PIC/IO-APIC line?

 -- Keir

On 25/7/08 06:34, "James Harper" <james.harper@xxxxxxxxxxxxxxxx> wrote:

> Am I correct in saying that setting HVM_PARAM_CALLBACK_IRQ to 0 disables
> interrupts in a HVM domain?
> 
> I'm finding that an interrupt in a HVM domain is getting called well
> after I do the above. My theory is that there is something about the way
> HVM stuff works that an interrupt could be 'in the pipeline' and could
> still occur even though I set HVM_PARAM_CALLBACK_IRQ to 0 and mask off
> the interrupts (evtchn_upcall_mask = 1 for all CPU's)
> 
> If that could happen, I'll need to work around it...
> 
> Thanks
> 
> james
> 
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