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

["Mark Hurenkamp" <mark.hurenkamp@xxxxxxxxx>]

> Is this a bug in something (kernel or hypervisor) or a known limitation
> with pci passthrough...  I sure hope it's a bug, cause I need to fill all
> my PCI slots with cards that are going to get passed into different
> domUs...  :-/

I'm also very curious if this will be resolved at some point, so far I've
run into similar problems using both 3.4-testing as well as 4.0.

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.

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?


Mark.




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