[Xen-users] PCI passthrough of cciss HBA

[Matthias Reif <mattreif@xxxxxxxxxxxxx>]

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?

Thanks
Matthias



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

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