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RE: [Xen-devel] edge-triggered interrupts in non-ACPI SMP HVM

  • To: "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: "He, Qing" <qing.he@xxxxxxxxx>
  • Date: Fri, 27 Oct 2006 16:17:10 +0800
  • Delivery-date: Fri, 27 Oct 2006 01:17:34 -0700
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: Acb5bmr5DsagoLgHQlW5UdZ56CmEKgALiFJWAAB94FA=
  • Thread-topic: [Xen-devel] edge-triggered interrupts in non-ACPI SMP HVM

It's not guest complaining, it's hypervisor who complains.
There are such lines in vioapic.c:
        DPRINTK("Forcing edge triggered APIC irq %d?\n", irq);

The guest crashed here when insmod platform-pci driver. So that means guest 
considers the irq as edge triggered. (in fact, if hypervisor does not 
intentionally crash, the guest is likely to work happily).

Later I checked Linux source, when ACPI is disabled, Linux read MP table to 
decide irq to I/O APIC binding. This is where it sets the trigger mode of irqs. 
See arch/i386/kernel/mpparse.c and arch/i386/kernel/io_apic.c

Mp talbe is constructed in hvmloader/mp_table.c, which has only ISA bus...

>-----Original Message-----
>From: Keir Fraser [mailto:Keir.Fraser@xxxxxxxxxxxx]
>Sent: 2006年10月27日 15:50
>To: He, Qing; xen-devel@xxxxxxxxxxxxxxxxxxx
>Subject: Re: [Xen-devel] edge-triggered interrupts in non-ACPI SMP HVM
>On 27/10/06 3:20 am, "He, Qing" <qing.he@xxxxxxxxx> wrote:
>> However, there is only one bus entry in that table, ISA. All the
>> interrupts is related to ISA bus and their trigger mode is set to
>> `follow bus', which Linux sets to edge triggered later.
>> I don't know whether lacking a PCI bus entry was OK, but now it turns
>> out to have problem with the pv driver. Is this going to be fixed?
>That's odd, since the guest should see the PV platform device as a PCI
>device just like any other (IDE, rtl8139, ...). So I wonder why the guest
>only complains about the PV platform device?
> -- Keir

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