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Re: [Xen-users] ATI VGA Passthrough / Xen 4.2 / Linux 3.8.10

Thanks for posting the results Gordan, unfortunate that it isn't
working as well as we hoped.

I haven't given up _quite_ yet.

I discovered yesterday that it _looks liks_ one of my PCIe slots is
actually duff (two different GPUs both fail to detect properly in it
but work fine in other slots).

If it turns out to be a duff slot, there's no telling what else
might be duff on the motherboard and how it might affect various
things, even though several days of full load stability testing

So some more bare-metal testing seems to be called for - right now I
am not prepared to disregard the possibility that maybe I have a
hardware issue somewhere that despite EDAC and ECC on everything,
remains undetected and unreported in the logs.

I hope you manage to resolve it, though I feel the NF200 will be the larger challenge.

 2) My motherboard's PCIe slots are behind NF200 PCIe bridges (yes,
EVGA have decided in their infinite wisdom to put all 7 PCIe slots
behind NF200s, none are directly attached to the Intel NB).

ÂI'm so sorry :P. NF200 has probably caused a lot of xen tinkerers to
Âutter a few dozen cuss words a piece.

ÂI can believe that. What is the solution, though?

ÂThe thing that drives me really nuts about the issues I'm seeing
(which may or may not be specifically related to the NF200) is that it
is so intermittent. It works well enough to boot up and work with a
gaming type load for a few minutes. Then something happens that causes
the VGA card to require a reset, and it all falls apart.

My solution was to buy another motherboard, I had no luck at all
passing the devices behind the NF200, and similar to your situation
all but one PCIe slot on that board was behind that bridge.

Did you not manage to get it working at all? Or was it just
intermittent like in my case? I can typically get about 5 minutes of
gaming out of my ATI card before it all goes wrong.

Ironically, I was thinking about an Asus Sabertooth with an 8-core AMD,
but opted to go for broke and get a couple of 6-core Xeons and an
EVGA SR-2. It turns out, a solution that is 4x more expensive isn't
actually better... :(

I was unable to get it working at all. ÂThe NF200 simply threw errors that 100% prevented me from passing the device. ÂI think it was missing a number of specific features required for passthrough, and I vaguely remember running lspci -vvv to verify what was missing. ÂPerhaps not all NF200's are created equal?
 What about with PCIe devices behind NF200 bridges? I know the NF200s
don't support PCI ACS, but that is a security feature (which I have
disabled enforcement of to get this far), and AFAIK shouldn't actually
affect the basic PCI passthrough capability.

ÂQuestion: how'd you disable ACS? ÂI think it may be causing me some


Â(pci-passthrough-strict-check no)
Â(pci-dev-assign-strict-check no)

Âin /etc/xen/xend-config.sxp

ÂIf it was causing you issues, however, I'd expect you to find errors
in logs pointing at it.

As I understand the xend-config.sxp [1] is for the xm toolstack and
deprecated Xend service.

xm toolstack and xend are what I am using. I have read reports of issues
with VGA passthrough using the xl stack so I didn't even attempt to use it.

The xm toolstack was deprecated in version 4.1. ÂI read that it had not been updated in months due to a lack of maintainers. ÂI did try xm back when I started, the passthrough worked but had the same problems I had when I began testing xl. ÂI have been using xl since then. ÂMy logic was simply "why become dependent on a tool that is no-longer maintained and may be removed from the next release?"

Does anyone know whether the xm toolstack been modified since 4.1 to accommodate changes with Xen 4.2? ÂIf it has not, it might be worth considering xl.

Perhaps I am confused, or things changed while I wasn't looking, but
for me enabling Xend breaks the xl toolstack. ÂMy understanding is it
was for the xm toolstack only and deprecated with 4.2. ÂAny chance
you can share how you configured it to work? ÂApparently it is
required to get libvirt working, which I also did not know was
compatible with Xen 4.2.

It is possible I'm the one doing it wrong. I'm on EL6, and using
virt-manager (at least for things it is willing to do), and that
defaults to the xm stack and xend.

For what it's worth, it works for the most part - apart from VGA
passthrough crashing within 5 minutes of gaming.

If you are using xm then it makes sense, as libvirt seems to require xm/xend to be loaded in order to function.

There are moreÂupgrade notesÂabout xend now, so that is new to me. ÂAccording to the Xen Man Pages the xend-config.sxp file doesn't have the flags you added; can you link to resources that mentioned them? ÂI have not seen xl equivalents for your xend configuration, so I guess xm does have some features xl does not still.

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