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

To: Jan Beulich <JBeulich@xxxxxxxxxx>, Florian Wagner <f_wagner@xxxxxxxxxx>
Subject: Re: [Xen-devel] Xen, IRQ-sharing and PCI passthrough
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Tue, 07 Jul 2009 08:39:22 +0100
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On 07/07/2009 08:32, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:

>>>> 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
> device).

Another thought is that the toolstack should be trying to reset the device
during domain destroy. I'm not certain that's always possible and always
done though (HVM passthru is better tested than PV passthru).

 -- Keir

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