Re: [Xen-users] pci passthrough how to that works?

[Matthias Reif <mattreif@xxxxxxxxxxxxx>]

xen-users-bounces@xxxxxxxxxxxxxxxxxxx wrote on 07/01/2010
09:32:23 AM:

> Hi,
> 
> I'm running Centos 5.3 for dom0 and domUs and using Xen 3.4.1 (AMD
V  
> enabled Sun box).
> 
> Using lspci, I see that my device I wished ignored by dom0 so that
I  
> can use it for 1 of my domUs is;
> 
> 07:00.0
> 
> In grub.conf, I added this to my module line;
> 
> pciback.permissive pciback.hide (07:00.0)
> 
> Upon reboot, lspci on dom0 still shows that pci device.
> 
> I've also modded my modprob.conf;
> 
> options pciback hide=(07:00.0)
> 
> Any ideas how I can get pci passthrough to work?
> 
> - Brian
> 

The pciback module needs to be loaded into initrd,
so it can seize the device at boot time.
Your boot log should confirm this if it says something
like "unknwon kernel option pciback.hide
ignoring."

Try something like this:

mkinitrd -f --preload=pciback /boot/initrd-$(uname
-r).img $(uname -r)

Also, pciback has to be loaded before the driver for
your device. This is not always the case.
I tried to seize a SCSI controller to pass a tape
drive to a domU, but its driver had to be loaded
first to get access to the disks where the initrd
etc is stored (I presume). When pciback was loaded
the driver had already taken control of the device.
If that's the case, late binding may be an option
for you, where you unbind the driver from the 
device after the system has booted and then bind it
to pciback prior to starting your domU.

Eg.
# echo -n 0000:07:00.0 > /sys/bus/pci/drivers/<your_driver_name>/unbind
# echo -n 0000:07:00.0 > /sys/bus/pci/drivers/pciback/new_slot
# echo -n 0000:07:00.0 > /sys/bus/pci/drivers/pciback/bind


Matthias




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