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

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 19/02/2010 19:14, "Michael D Labriola" <mlabriol@xxxxxxxx> wrote:

>> IRQ on domU.  :-)
>> 
>> Now we just have to get a better fix for dom0 than commenting out the
>> entire note_interrupt() function...
> 
> Actually, I just verified that that patch makes the note_interrupt()
> gutting unnecessary.  With just that one line changed, I'm up and running
> perfectly.

Yeah, that probably means that pv_ops already has logic to disable that
spurious interrupt logic when an interrupt is shared between multiple
guests. If your domU was failing to bind to the interrupt line, that would
mean the interrupt would not appear to be shared (from dom0 kernel pov) and
then when the domU-passed-thru device starts generating interrupts dom0
acted on them as really spurious (since it thinks it owns all devices that
might generate that interrupt). So the note_interrupt() hack treated that
symptom but not the actual original cause of the troubles.

Interestingly, that does mean this is a way an errant domU can really spoil
dom0's day....

 -- Keir



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