Re: [Xen-users] Re: PCI passthrough of cciss HBA

[Matthias Reif <mattreif@xxxxxxxxxxxxx>]

xen-users-bounces@xxxxxxxxxxxxxxxxxxx wrote on 30/09/2009
07:05:39 PM:

> Matthias Reif wrote:
> > 
> > All,
> > 
> > I would like to run the following issue past the list to confirm
that my 
> > problem analysis makes sense or whether I missed something:
> > 
> > We have a HP ML370G6 server with VT-x and VT-d enabled in the
BIOS. It 
> > is equipped with two Smart Array HBAs - one connected to the
HDD array 
> > (SmartArray P800) and one connected to an LTO tape drive (SmartArray
> > P212). Both controllers use the same driver on the dom0 (cciss).
> > 
> > dom0 OS = CentOS 5.3 Linux 2.6.18-164.el5xen x86_64
> > Xen = 3.4.1
> > 
> > My plan was to use PCI passthrough to give a domU unrestricted
access to 
> > the tape drive. However, I have been unable to get pciback to
seize the 
> > P212 controller at boot time.
> > 
> > Firstly, I modified the initrd to preload the pciback module:
> > 
> > # mkinitrd -f --preload=pciback /boot/initrd-$(uname -r).img
$(uname -r)
> > 
> > Then I added the following lines to modprobe.conf:
> > 
> > options pciback hide=(0000:10:00.0)
> > install cciss /sbin/modprobe pciback ; /sbin/modprobe --first-time
> > --ignore-install cciss
> > 
> > grub.conf:
> > 
> > title CentOS (2.6.18-164.el5xen)
> >        root (hd0,0)
> >        kernel /boot/xen.gz-3.4.1 iommu=1
> >        module /boot/vmlinuz-2.6.18-164.el5xen
ro root=LABEL=/
> >        module /boot/initrd-2.6.18-164.el5xen.img
> > 
> > 
> > NB: Passing pciback.hide=(0000:10:00.0) as a kernel parameter
does not 
> > work:
> > 
> > kernel: Unknown boot option `pciback.hide=(10:00.0)': ignoring
> > 
> > I believe this is because the pciback driver is compiled as a
module in 
> > the CentOS stock kernel.
> > 
> > 
> > After booting with the above config the cciss driver has taken
control 
> > of PCI device 000:10:00.0 instead of the pciback module.
> > 
> > 
> > It seems the pciback module is loaded after the HBA driver (cciss)
and 
> > therefore does not get a chance to seize the Smart Array P212
> > controller. This is most likely because the pciback driver is
compiled 
> > as a module instead of into the kernel. The cciss driver is loaded
first 
> > to gain access to the hard drive array (via the P800 controller)
and to 
> > load the pciback module and its configuration. At that point
it is too 
> > late for pciback to gain control of the Smart Array Controller
as the 
> > cciss driver has already bound to it.
> > 
> > I belive to fix this I would have to recompile the CentOS kernel
with 
> > the pciback compiled in statically. Is that correct or is there
any 
> > other way?
> > 
> 
> 
> Using the pciback kernel or module option is not the only way to have
> pciback seize a device. You could use calls to the sysfs structure
to 
> unbind the device from the cciss driver and then assign it to pciback.
> 
> Something along those lines might work after loading pciback:
> 
> echo -n '0000:10:00.0' > /sys/bus/pci/drivers/cciss/unbind
> echo -n '0000:10:00.0' > /sys/bus/pci/drivers/pciback/new_slot
> echo -n '0000:10:00.0' > /sys/bus/pci/drivers/pciback/bind
> 
> Make sure you are not using any of the resources (i.e. exclude this
is 
> vgscan or automounts) to avoid unexpected results...
> 

Thanks for your suggestion. I tried your approach,
but for some reason the unbind command freezes. There is nothing in the
logs that indicates why.

Thanks
Matthias



SOUTH PACIFIC SEEDS
PO Box 934, GRIFFITH N.S.W. 2680. AUSTRALIA
Phone: 02 6962 7333      Fax: 02 6964 1311

---

CAUTION: The information contained
in this e-mail is privileged and confidential. If you are reading this
message and you are not the intended recipient, you are hereby notified
that any use, dissemination, distribution or reproduction of all or part
of the contents is prohibited. If you receive this message in error, please
notify the sender immediately. Any opinions or views expressed in this
message are those of the individual sender and may not represent those
of their employer.

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users