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[Xen-users] RE: DomU can't access PCI Parallel port (was SVM not detecte

To: "Brian P. Martin" <Brian@xxxxxxxxxxxxxxxxxxxx>
Subject: [Xen-users] RE: DomU can't access PCI Parallel port (was SVM not detected on Opteron 1220)
From: <djmagee@xxxxxxxxxxxx>
Date: Wed, 29 Jul 2009 11:23:44 -0400
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Thread-topic: DomU can't access PCI Parallel port (was SVM not detected on Opteron 1220)
As far as I know there's no way to explicitly map ioports or irqs;
xen/dom0 takes care of this for you.  There has been some discussion
lately about IRQ sharing and PV passthrough, as the requirements seem to
change with versions of xen. (Most development seems to be geared
towards iommu assisted passthrough.)  You may have to fiddle with
pciback.permissive settings, but I have no experience needing to do this
so I couldn't tell you what the procedure is.

The best way to get help from this list will be to post all the relevant
logs and configuration files you have.  This includes your
/var/log/xen/qemu-...log for the domain, and any relevant system
messages in the domu.  I'd include lspci -vvv output from the domu, and
try to see if you get any messages when you load the appropriate driver
for the card in domu, for example, check dmesg or syslog after a
modprobe parport (or whatever the driver is, it's been years since I've
used anything on a parallel port), and see if there's any output
whatsoever pertaining to your device.

-----Original Message-----
From: Brian P. Martin [mailto:Brian@xxxxxxxxxxxxxxxxxxxx] 
Sent: Wednesday, July 29, 2009 12:31 AM
To: djmagee@xxxxxxxxxxxx
Cc: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: DomU can't access PCI Parallel port (was SVM not detected on
Opteron 1220)


> Your DomUs will only see the emulated hardware.  To see your real
> hardware inside a DomU you will have to pass it through.  Without the
> appropriate hardware, you'll only be able to pass-through hardware to
> PV guest.  Since you're on AMD, I'm going to have to assume you don't
> have IOMMU hardware, as they haven't sold any yet that I know.  Google
> searches for the right keywords will reveal more than enough info you
> can piece together to achieve this, but here's a short summary:
> Make sure pciback is available in your Dom0 kernel (either built-in or
> as a module).
> Identify PCI device you want to hide, likely using lspci
> If pciback is builtin, then you'd have to add a 'pciback.hide=(...)'
> the Dom0 kernel line in grub and restart
> Otherwise, you can hide the device after startup as described here:
> a
> s_module
> Assign the device to your DomU with a pci = [ '...' ] line the
> configuration file
> I don't have any experience with PV passthrough, but it should be
> easier, though less stable/secure than HVM passthrough.  Also, lately,
> xen pci pass-through development has focused mostly on iommu backed
> passthrough, and I've read messages suggesting there are more
> restrictions to pv passthrough in more recent versions of xen.

Thanks for the great summary.  I've already been through this, but your
helped me check my work.  DomU still seems to know that the device is
but can't talk to it.  In addition to the pci= statement, do I need to
IOPORTs and/or IRQs? 


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