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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 16:30:38 +0800
  • Delivery-date: Fri, 27 Oct 2006 01:31:02 -0700
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: Acb5bmr5DsagoLgHQlW5UdZ56CmEKgALiFJWAAB94FAAADz8HwAAcdlQ
  • Thread-topic: [Xen-devel] edge-triggered interrupts in non-ACPI SMP HVM

>-----Original Message-----
>From: Keir Fraser [mailto:Keir.Fraser@xxxxxxxxxxxx]
>Sent: 2006年10月27日 16:11
>To: He, Qing; xen-devel@xxxxxxxxxxxxxxxxxxx
>Subject: Re: [Xen-devel] edge-triggered interrupts in non-ACPI SMP HVM
>On 27/10/06 9:17 am, "He, Qing" <qing.he@xxxxxxxxx> wrote:
>> 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...
>Yes, but why does the guest set only this PCI device's IRQ to
>edge-triggered? Why not the rtl8139, for example? Neither is explicitly
>listed in the MP tables, so where does this differing behaviour come from?
> -- Keir

Per my understanding, rtl8139 works fine even if it is edge-triggered, because 
there is no interrupt sharing. So if there is no platform pci device, it is 
possible for guest to set all devices to edge triggered without complaining 
anything. (I do know that if I comment out sanity checks in HV, platform pci 
device works fine in edge triggered mode, and there will be no complaints.)


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