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Re: [Xen-devel] Xen, IRQ-sharing and PCI passthrough

To: "Florian Wagner" <f_wagner@xxxxxxxxxx>
Subject: Re: [Xen-devel] Xen, IRQ-sharing and PCI passthrough
From: "Jan Beulich" <JBeulich@xxxxxxxxxx>
Date: Tue, 07 Jul 2009 08:32:28 +0100
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>>> Florian Wagner <f_wagner@xxxxxxxxxx> 07.07.09 08:19 >>>
>Is there some other way to fix this than making sure the cards don't
>share IRQs (which is quite a hassle when building a significant number
>of machines with this configuration but with slightly different
>hardware)? A fix from a newer Xen release we could backport to our
>Debian kernel perhaps?

Assuming your kernel has a call to irq_ignore_unhandled() out of
note_interrupt(), there's nothing but using hardware's help (i.e. VT-d
interrupt remapping) to get this addressed: The pv passthrough
mechanism assumes that guests you assign physical devices to are well
behaved, and your guest isn't (it fails to disable the interrupt at the


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