[Xen-users] Same IRQ in dom0 and domU by different hardware causes dom0 crash

[Iñaki Baz Castillo <ibc@xxxxxxxxxxxx>]

Hi, this is my first mail in this list. I've installed Xen in Debian Etch and 
created a virtual domU Debian Etch as well.

In domU I've installed an Asterisk and want to use a Beronet ISDN card:

  ~# lspci
  0a:01.0 ISDN controller: GmbH ISDN network Controller [HFC-4S] (rev 01)

So I pass the iSDN card PCI to domU by adding in dom0 "/boot/grub/menu.lst":
---
module /boot/vmlinuz-2.6.18-4-xen-686 root=/dev/sda1 ro pciback.hide=(0a:01.0)
---

After that, I see the PCI in domU:

  ~# lspci
  00:00.0 ISDN controller: GmbH ISDN network Controller [HFC-4S] (rev 01)


-- PROBLEM --
My first problem is that dom0 and domU share IRQ 18:

** dom0 **
  ~# cat /proc/interrupts
              CPU0           CPU1
   18:      14140          0        Phys-irq  uhci_hcd:usb3

** domU **
  ~# cat /proc/interrupts
              CPU0
   18:      16507        Phys-irq  HFC-multi

Obviously, the interrupts so big number by IRQ18 in dom0 is "false", they are 
in fact interruptions of the HFC card in domU.

If I reboot or destroy domU I get a dom0 message:
  Disabling IRQ #18

and dom0 looses net, keyboard and so. I must restart it.


-- WORKAROUND --
I can quit the module "uhci_hcd" in dom0 which is using IRQ 18 and the problem 
dissapears, but of course it's not a good/clean solution.

But I have another problem with this workaround: I'd like to quit this module 
for the start by adding to "/etc/modprobe.d/blacklist":
  blacklist  uhci_hcd

but it doesnt' work and the module is loaded anyway. I can't understand 
because I use that method to avoid loading other modules in the same Debian 
Etch and it works. Any idea about this problem?


-- SOLUTION --
I'd like a way to dissable IRQ 18 in dom0. Anyway I think that the only 
solution is by editing the Bios and dissabling or chanching that IRQ (haven't 
tryied it yet) but I'd like to listen to other suggestions.


-- POSSIBLE BUG? --
Waht I really care is this IRQ sharing between dom0 and domU by different 
hardware. Is it really normal?
I've found other case exactly the same as mine without no response:
  http://lists.xensource.com/archives/html/xen-users/2006-05/msg00967.html



Thanks for any help.

Regards.


--
*Iñaki Baz Castillo*
ibc@xxxxxxxxxxxx

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