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

To: "He, Qing" <qing.he@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] edge-triggered interrupts in non-ACPI SMP HVM
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Fri, 27 Oct 2006 09:11:13 +0100
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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



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