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

To: Florian Wagner <f_wagner@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Xen, IRQ-sharing and PCI passthrough
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Tue, 07 Jul 2009 08:22:40 +0100
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On 07/07/2009 07:19, "Florian Wagner" <f_wagner@xxxxxxxxxx> wrote:

> My take on this: Xen (or rather the dom0 kernel?) disables the shared
> IRQ, which at that time is still in use by the other card. In my case
> this crashes the machine, since the IRQ is shared with the RAID
> controller (sometimes resulting in destroyed filesystems).
> 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?

Newer versions of Xen, and suitably modern ports of the XenLinux patchset,
support MSI interrupts. That would avoid the whole issue of interrupt
sharing, if either the RIO Specialix or your RAID card supports MSI.

Otherwise, can you not rely on cleanly shutting down the domU? Th eproblem
is probably that the interrupt line gets wedged high because the domU device
has an interrupt pending but the domU is no longer around to service it.

 -- Keir

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