[Xen-devel] HVM windows - PCI IRQ firing on both CPU's

["James Harper" <james.harper@xxxxxxxxxxxxxxxx>]

I'm just doing some testing on the gplpv drivers with different ways of
handling interrupts, and I'm trying a scheme where each xen device (eg
vbd/vif) driver attaches to the same IRQ as the pci driver, and each
handles it in sequence.

In testing though, I noticed the following when logging what each ISR is
doing:

60.32381439 - evtchn event on port 5
60.32384109 - port 5 handler (does some work)
60.32386780 - port 6 handler
60.32389069 - port 7 handler
0.00616564 - evtchn nothing to do
0.00619481 - port 5 handler
0.00621962 - port 6 handler
0.00624393 - port 7 handler

The first number is the timestamp (why is the TSC so far out of whack
between CPU's??? Is that a hardware thing or a Xen thing? It causes huge
problems with 'ping' too!!!), the second is the isr that is running.

Why is the ISR getting run again immediately on the other CPU? Is this
an OS thing or am I not acking the interrupt correctly?

Thanks

James

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