Re: [Xen-users] PCI passthru

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> I have been trying to get PCI passthru to work for a while now.
> I am running 3.3-unstable on Centos 5.1. I have a Intel XEON
> 5140 CPU, with the latest BIOS.

I'll assume that you're wanting to pass through to a PV domain.  HVM domains 
can have PCI devices assigned as long as your hardware has VT-d (most 
doesn't, currently!).  Passing to a PV domain should still work, regardless.

> I would like to be able to pass the SAS raid controller from
> dom0 to dumU.

Please be aware that assigning a PCI device to a domU without having VT-d 
enabled makes it as privileged as dom0: a determined attacker who gains 
control of the domain has the ability to own an entire host.  A domU with PCI 
passthrough isn't given direct control over the whole machine but it can, in 
principle, abuse its PCI device to get it.

You might also want to do a quick googling / searching of the mailing list 
archives to make sure nobody has had any problems with these before.  Some 
PCI devices are unco-operative in various ways (either due to hardware or 
driver problems) and that can make them fail to work under PCI passthrough.

> Do I need to do anything special to domU? It is running Fedora
> core 4.

You need to be running a suitable kernel on it.  I'd suggest that you try 
using your dom0's kernel (and modules), since that will definitely match the 
correct interfaces.

> Is there any real documentation available on how to configure
> PCI passthru on both dom0 and dumU?

There's some here:
http://www.cl.cam.ac.uk/research/srg/netos/xen/readmes/user/user.html#SECTION03230000000000000000

And some more here:
http://wiki.xensource.com/xenwiki/Assign_hardware_to_DomU_with_PCIBack_as_module

Take the docs with a pinch of salt, since they sometimes get out of date.

Cheers,
Mark

-- 
Push Me Pull You - Distributed SCM tool (http://www.cl.cam.ac.uk/~maw48/pmpu/)

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