Re: [Xen-devel] Interrupt for HVM guests

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 05/06/2009 19:43, "Emre Can Sezer" <ecsezer@xxxxxxxx> wrote:

> I am trying to figure out how an HVM guest is passed an interrupt.  Say
> that a network packet has arrived and the QEMU driver in dom0 has to
> notify an HVM guest of the packet's arrival.  Could someone please give
> a brief, high-level description of this process?  I read the Intel
> Architectures Software Developer's Guide on VM Execution bits and
> Virtual interrupts and also some Xenwiki stuff about it but I'm still
> not sure what's going on.  I don't have any device pass-through or
> stubdom or PV Drivers for my HVM guest.  I would also appreciate
> references to some Xen files/functions related to this process.

Following will give you enough to grep around for the details:
Hypercall is HVMOP_set_pci_intx_level: qemu-dm uses this to assert a PCI
INTx virtual interrupt line. Handled by hvm_pci_intx_assert() ->
vioapic_irq_positive_edge() -> vioapic_deliver() -> ioapic_inj_irq() ->
vlapic_set_irq()&vcpu_kick(). Final function there wakes the guest vcpu
which on vmentry calls vmx_intr_assist() -> hvm_vcpu_has_pending_irq() ->
vlapic_has_pending_irq(), which will return a pending vector.
Vmx_intr_assist() then delivers that vector via vmx_inject_extint().
Hardware then delivers the interrupt automatically during vmentry.

 -- Keir



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