Xen devel - Mar 2009 - patch to assign PCI device on VM without address translation

Hi everybody,
we are two french students working for EADS to assign PCI device to VM with
Xen.
We had a problem to use some National Instruments PCI Card. These cards have
2 Base Address Register of 4K each, and their driver write in the
BAR1''s
address in a register of BAR0. But since the driver can''t know physical
addresses, it write the wrong address, and the card can''t initialize
her
BAR.
We worked on it several days, and come up with a solution : force physical
and virtual BAR addresses to match.
We are currently doing that thanks to a small change in the function
"pt_pci_write_config" in the file tools/ioemu-remote/hw/pass-through.c
from
the xen unstable tree.
We add a "if" which check what BAR address the function has be given
as
argument. If this address is the usual address where Xen map the BAR of our
card, we change it''s value for the physical one.
We made tests with this patch, and our cards worked fine.
So we would like to make a patch for Xen to add a mode "1:1 mapping"
for
assigned device, using a configuration file (something like the
xend-pci-quirks.sxp file in etc/xen) where each users could add their own
card.

Since we set our background, and if you''re still reading, we assume
that you
think this patch could be useful.
Now, it''s question time :
    Do you think we should move virtual addresses to match physical
addresses (changes in QEmu) or move physical addresses to match virtual
adresses (change in Dom0)?
    Do you have any idea how addresses are choosen, in a VM or in the Dom0,
or in which order?

Thanks to you for reading,
We''ll be glad to hear your comment about our idea. Feel free to send us
a
private e-mail just to share your point of view, or answer on the mailing
list.
Best regards,
Léonard & Guillaume


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