Greetings,
I configured my dom0 to hand a 3com NIC through to a guest:
# Unbind a PCI network card from its network driver
echo -n .&checktime(0000,04,0,':')d.0 > /sys/bus/pci/drivers/3c59x/unbind
# and now tell PCI Backend to watch the slot.
modprobe pciback
sleep 5
echo -n .&checktime(0000,04,0,':')d.0 > /sys/bus/pci/drivers/pciback/new_slot
# Now that the backend is watching for the slot, bind to it
echo -n .&checktime(0000,04,0,':')d.0 > /sys/bus/pci/drivers/pciback/bind
This works fine; the guest sees the NIC after the guest's py file is updated
appropriately:
pci = [ '04:0d.0' ]
What happens:
This setup works for awhile.
The interrupt for the NIC is shared with another device used by dom0. In the
best case, dom0 and the guest are running on separate CPUS, and the
interrupt driver in dom0 is called whenever a packet comes in the guest,
which is unnecessary work, imho. In the worst case, when dom0 and the guest
are sharing a CPU, and the dom0 device sharing the interrupt is something
like the disk subsystem, dom0 and the guest appear to steal interrupts from
one another, and dom0 and all the guests grind to a halt (no disk I/O in
this example).
I've tried various techniques (kernel parameters in dom0) to ensure that the
interrupt assigned to the guest's NIC is *not* shared in order to avoid
this problem, to no avail.
Any suggestions for how to influence the interrupts that are assigned to
devices in dom0? It seems that there are a number of physical interrupts
that are not used, and some are shared:
 CPU0
 1: 2 Phys-irq-level i8042
 6: 5 Phys-irq-level floppy
 8: 1 Phys-irq-level rtc
 9: 0 Phys-irq-level acpi
 14: 89901 Phys-irq-level libata
 15: 9347 Phys-irq-level libata
 16: 0 Phys-irq-level uhci_hcd:usb1
 17: 682628 Phys-irq-level uhci_hcd:usb2, peth0
 18: 96245 Phys-irq-level aic7xxx
 19: 356 Phys-irq-level Intel 82801BA-ICH2, eth1
256: 263502 Dynamic-irq-level timer0
257: 0 Dynamic-irq-level resched0
258: 0 Dynamic-irq-level callfunc0
259: 3823 Dynamic-irq-level xenbus
260: 180 Dynamic-irq-level console
261: 18936 Dynamic-irq-level blkif-backend
262: 9431 Dynamic-irq-level blkif-backend
263: 20035 Dynamic-irq-level blkif-backend
264: 44080 Dynamic-irq-level vif1.0
265: 12878 Dynamic-irq-level blkif-backend
266: 1071 Dynamic-irq-level vif4.0
267: 3352 Dynamic-irq-level vif2.0
268: 17074 Dynamic-irq-level blkif-backend
269: 5598 Dynamic-irq-level vif5.0
270: 118463 Dynamic-irq-level vif3.0
One would think that if the physical interrupts are available, and the
device can be configured to use them, that no sharing would occur until the
system allocated all the physical interrupts.. 
TIA,
Mike
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel