Re: [Xen-devel] PCI passthrough w/ shared IRQ in xen/master

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 19/02/2010 16:15, "Mark Hurenkamp" <mark.hurenkamp@xxxxxxxxx> wrote:

> When you do passthrough the device which has a shared IRQ, the domU will
> load the appropriate driver, but Xen refuses to assign the IRQ to the
> domU.
> In your case (and mine as well), the driver in domU is not aware that it
> has no IRQ, and thus starts generating interupts which are then caught by
> Dom0 as spurious interrupts, in my case even causing Dom0 to crash at
> times.

Are you sure the domU doesn't get the interrupts as well? Correct behaviour
in Xen will be to send the interrupt to both dom0 and domU - since Xen can't
work out which of the two it properly belongs to (and it could be both).

I would suggest try commenting out the content of the function
kernel/irq/spurious.c:note_interrupt(). That will stop dom0 from reacting to
the 'spurious' irqs that it sees and ignore them instead. See if that works
for you.

 -- Keir

> My way around this, is to try and move the other device IRQs out of the
> way (the ones that matter seem to be MSI capable), but i understand that's
> not always possible.
> If your other device is PCI based, and has no MSI, then for now I'm
> affraid you're out of luck...
> 
> Like you, I do hope this is considered a bug that will be fixed in a later
> release... anyone know what the xen policy is on this?



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