[Xen-devel] Re: Losing PS/2 Interrupts

[Thomas Goetz <tcgoetz@xxxxxxxxx>]

On May 19, 2011, at 5:45 PM, Thomas Goetz wrote:

> I'm running PVOPs 2.6.38 on Xen 4.0.2 RC3 and while booting a guest I lose 
> interrupts for the PS/2 trackpad. The trackpad stops functioning because the 
> device is waiting for service. I added a work around that calls 
> i8042_interupt form a timer if it hasn't been called in 1s and it started 
> working again. I added some code to Xen to count IRQ 12 and compared that to 
> the IRQ 12 count in //proc/interrupts (I stopped PS/2 activity and waited for 
> PS/2 interrupt activity to stop before taking the counts). I lose one 
> interrupt in Dom0 every time the trackpad freezes.
> 
> 
> (XEN) IRQ 12 count 21048
> 12:      21047          0  xen-pirq-ioapic-edge  i8042   <--- lost an 
> interrupt in dom0
> ...
> 
> (XEN) IRQ 12 count 48540
> 12:      48537          0  xen-pirq-ioapic-edge  i8042   <--- lost 3 
> interrupts in dom0
> 
> 
> I looked at the point at which the trackpad gets it's last interrupt in a 
> trace and the other major activity at that time is the event channel that 
> services the Qemu vcpu io_req code.
> 
> This 2.6.38 tree has a merge of Stafano's 2.6.39 fixes in 
> drivers/xen/events.c.
> 
> Anyone have any ideas or suggestions?
> 


More data. The number of missing interrupts is equal to the number of times 
__do_IRQ_guest called send_guest_pirq and incremented already_pending. The 
number of IRQ 12 interrupts reported by /proc/interrupts is the same as the 
count of times __xen_evtchn_do_upcall called generic_handle_irq_desc for IRQ 
12. So the issue has to be between send_guest_pirq in Xen and  
__xen_evtchn_do_upcall in dom0.


-Tom Goetz






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