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Re: [Xen-devel] trigger an interrupt in HVM

To: James Harper <james.harper@xxxxxxxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] trigger an interrupt in HVM
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Thu, 21 Aug 2008 08:43:43 +0100
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Thread-topic: [Xen-devel] trigger an interrupt in HVM
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On 21/8/08 01:22, "James Harper" <james.harper@xxxxxxxxxxxxxxxx> wrote:

> I need to trigger an interrupt on the HVM Xen PCI device. Is this
> possible?
> Could I just set vcpu_info->evtchn_upcall_pending = 1 and then do a
> notify hypercall?

There is no such hypercall. In PV guests we can do any hypercall and the
evtchn_upcall_pending will be picked up. This isn't the case for an HVM
guest -- the IRQ is only asserted if an event is set pending by the
hypervisor itself.

If you must be able to trigger event delivery via the HVM IRQ mechanism from
within your HVM guest then I suggest you allocate an IPI event channel and
do a notify hypercall on that. That will have the side effect of triggering
an interrupt and 'flushing through' all other pending events.

 -- Keir

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